p1 of 10 26-Aug-10 USB-FileSys / USB-Config HW149-8 www.hexwax.com
USB-FileSysTM
Driver-free USB embedded file system (Previously USB-Config)
Summary
USB-FileSys is a low cost USB FAT file system. Its
memory area is accessed by a host controller using SPI
commands, and, when plugged into a USB port,
simultaneously appears on a PC like a file system on a
removable disk.
For low duty configuration and diagnostic applications,
USB-FileSys can use its own on-chip pre-formatted
8kByte flash memory area. For moderate file storage
and transfer, USB-FileSys can be interfaced to
Microchip 25AA1024 EEPROM for 128kByte storage.
For large file storage and transfer applications, USB-
FileSys can be interfaced to SD™ cards, and integrated
circuits with SD™ card interfaces, of up to 1GBbyte.
(Internal and SD options for 28-pin devices only.)
USB-FileSys uses the Mass Storage Device (MSD) USB
profile. It works without drivers on PCs running
Windows (ME or later), Mac (OS 9 or later) or Linux (4.0
or later). It is available pre-programmed as a 28-pin DIL
package and a 20 pin SSOP package.
Features
FAT12 / FAT16 file system, no licensing needed
True MSD plug and play, no drivers required
Works with internal flash memory, 25AA1024
external memory (128Kbyte) and SD compatible
cards and integrated circuits up to 1GB.
Partial support for long file names
USB 2.0 compatible
Applications
Consumer products, e.g. photo frames
Data logging
File transfer
Device configuration & diagnostics
Mechanical Specifications
Device pinout
Table 1. Device Pinout
Pin
DIL SS Name Description
20 1 Vdd Power positive input
9 2 OSC1 Oscillator input
10 3 OSC2 Oscillator output
1Media
Vpp
Media detect
TEAclipper Vpp
4RST#
Vpp
Device reset (Active low)
TEAclipper Vpp
11 5 MISO-M Data input from SPI memory
12 6 MOSI-M Data output to SPI memory
13 7 SCK-M Clock output to SPI memory
7 8 SSn-H Slave select input from host
18 9 MISO-H Data output to host
4 10 SSn-M Slave select output to SPI memory
22 11 SCK-H Clock input from host
3 12 Activity USB Activity Indicator
21 13 MOSI-H Data input from host
24 14 Sleep# Sleep control input (Active low)
5 15 PTO# Power take-off OK indicator (active low)
26 16 USB-S USB voltage sense
14 17 Vusb USB supply filter
15 D- USB data -
27 18 PGC TEAclipper PGC
16 D+ USB data+
28 19 PGD TEAclipper PGD
8,19 20 Vss Power ground reference
Firmware Factory Ltd
3 Plough Yard, Ground Floor
London EC2A 3LP, UK
sales@firmwarefactory.com
support@firmwarefactory.com
USB-FileSys
Looks like
Flash Drive
Serial Memory
Data Store
USB
Host
Figure 2
Embedded
Product
p2 of 10 26-Aug-10 USB-FileSys / USB-Config HW149-8 www.hexwax.com
Electrical Specifications
Table 2. Electrical Specifications
Operating voltage Vdd, 28-pin device 2.7V – 5.5V
Operating voltage Vdd, 20-pin device 1.8V – 5.5V
Typical/max supply current, Vdd = 5.0 10mA / 21mA
Typical/max Sleep current, Vdd = 5.0 0.1μA / 2μA
Operating Temperature -40°C to +85°C
Maximum SPI clock rate 1MHz
Basic Operation
To the host microcontroller (‘host’), USB-FileSys looks
like a file system accessed with SPI commands. To the
PC, it looks like a flash drive.
The use of the MSD USB profile means that no driver
installation is required. It is plug-and-play compatible
with PCs running Windows (ME or later), Mac (OS 9 or
later) or Linux (4.0 or later).
Pin Functions
The pin functions are shown in table 1. Pins marked n.c.
will be configured as inputs and, in order to minimize
power consumption, should not be left floating.
The pin functions are described in detail below.
Vss, Vdd, Vusb
Vss is the power supply ground reference. Vdd should
be connected to a regulated supply, most usually the
USB power when available and a battery when USB
power is not available. Vusb should be connected, via a
470nF capacitor, to Vss. See for example C8 in figure 4.
OSC1, OSC2
OSC1 and OSC2 should be connected to a 12MHz
parallel cut crystal circuit with 22pF capacitors or a
12MHz resonator with 0.25% total tolerance.
Vpp, PGC, PCD
TEAclipper programming pins. Refer to the TEAclipper
Programming section for details. Note that the Vpp pin
may be subject to voltages as high as 13V during
programming. On the 28-pin device, PGC and PGD will
be configured as outputs in normal use and should be
left floating when not being used for programming.
Media Detect
The Media detect input pin should be pulled low with a
33K resistor if 25AA1024 memory used. If the SCK-M
pin is biased low indicating that internal memory is used,
the Media detect pin is ignored.
The Media detect input pin should be high during normal
operation with SD memory. If SD memory removable,
Media detect should be taken low when it is removed. If
the device is connected to a PC, a soft detach and re-
attach will be performed on media removal. The SD
memory must be physically removed so that a power-up
reset is performed when it is re-inserted.
In order to allow USB-FileSys to be programmed in-
circuit, it must be possible to configure the application
circuit so that this input appears to be pulled high via a
22k resistor, or pulled low with a 33k resistor.
RST#
The 20-pin device has an active low pin in place of the
media detect pin. This should normally be biased high
with a 22k resistor.
D+, D-
USB data I/O. Refer to the USB Connectors section for
details of their connections.
USB Voltage Sense
This input should be high when the device is plugged
into a USB host. Refer to figure 5 for a typical method
of deriving this input from the USB supply input.
USB Activity Indication
Output that can either be used for connecting to an
activity indication LED, or for generating an interrupt
when an USB write event occurs.
If configured as an activity indicator, it is high for
approximately 100ms when USB status is changing, or
a USB command is being processed other than Test
Unit Ready. (Test Unit Ready is ignored because
operating systems send it approximately once per
second to verify the drive is still available.)
If configured as an interrupt, it can be set to output high
when the PC is executing a write to any sector, or a
write to the root directory entries. The primary purpose
of these functions is to allow the host to capture the date
and time information when the PC closes a file.
PTO#
The “Power Take-Off” output is low when power may be
drawn by the application circuit from the USB supply.
USB-FileSys device is configured to request up to
100mA, allowing the device to operate from unpowered
hubs. It may be reconfigured to request up to 500mA
using the Set Configuration command. If this is done
the device will work from PCs and powered hubs only.
If PTO# is high, the device should draw no more than
100μA. In no event should an external power source
inject power into the USB Vdd line.
Sleep
The Sleep input is be regularly polled. If it is low, the
device and its slave memory enter a low-power sleep
state. When sleep goes high, the device will resume
normal operation within 70ms.
SCK-M, MISO-M, MOSI-M, SSn-M
If SD or 25AA1024 memory is used, these pins are the
SPI serial interface to the memory. 4k7 pull-up resistors
are required on all these lines.
If internal memory is used, SCK-M should be biased low.
SCK-H, MISO-H, MOSI-H, SSn-H
In SPI communications with the embedded host, USB-
FileSys acts as an SPI slave device. USB-FileSys is
selected by transitioning SSn from high to low. At that
time, SCLK should be low (CPOL=0). On the rising
edge of SCLK, one bit of data is read on MOSI
(CPHA=0). On the falling edge of SCLK, the data on
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MOSI may be changed by the master. (This is also
known as Mode D or 0,0 operation.) See figure 3. The
actual commands are specified in the Host Commands
section.
Hi-Z Hi-Z
SSn
SCLK
MOSI
MISO
...
...
...
Command Response
...
1MHz max
Figure 3. SPI Timing Diagram
All commands from the host are followed by a response
from USB-FileSys. Since the time generated to
generate a response is indeterminate, USB-FileSys will
output bytes of value 0xFF until it can generate a valid
response. After issuing a command, the host should
repeatedly read data from USB-FileSys, waiting for a
byte with a value other than 0xFF. The Write File and
Set File Entry commands are each composed of two
such Command-Response exchanges.
USB-FileSys has been tested with SPI clock rates up to
1MHz.
Memory
Internal Memory
In order to maximize available storage space, the
internal memory is pre-formatted as a 16-sector FAT12
file system with 512 bytes per sector. (4 of these
sectors are required for the file system and root
directories.) Reformatting by the PC is not permitted.
The root directory can contain up to 16 entries, including
the volume name. Since long file names require
multiple directory entries, they are not recommended.
The volume is normally supplied containing no files. If
ordered in 5K+ quantities, files may be pre-loaded.
To indicate to USB-FileSys that the internal memory
should be used, the SCK-M input should be pulled low.
Pages of internal memory may be erased and rewritten
approximately 100K times. If file sizes change
frequently, the greatest wear will occur in the FAT tables
and the directory entry. Therefore if a file is to be written
to frequently, its size should be fixed.
This option is only available for the 28-pin device.
TQFP and SSOP packages are available, but they are
not in general distribution. Contact us for further
information.
External Memory – 25AA1024
For moderate storage applications, a Microchip
25AA1024 memory (128kByte storage) may be
connected to the MISO-M, MOSI-M, SCK-M and SSn-M
lines. A 4k7 pull-up resistor should be provided for
SCK-M. The media detect input should be permanently
biased low.
When first used, the memory will automatically be
formatted as a 16-sector FAT12 file system with 512
bytes per sector. The PC may re-format the drive if
required.
External Memory – SD card / integrated circuit
For large storage applications, an SD-compatible
memory of up to 1GB may be connected to the MISO-M,
MOSI-M, SCK-M and SSn-M lines. 4k7 pull-up resistors
should be provided for these lines, and also for unused
SD card I/O pins.
The memory can be a removable SD card or a SD-
compatible chip. If the memory is removable, the media
detect input should be connected to a switch to indicate
when the card is present. Devices with SD card readers
will be able to read the data on the SD card directly.
Memories larger than 1GB will be ignored, as will non-
standard memories which do not have block sizes of
512 bytes. San-Disk products are used for testing.
Pages of SD memory are typically wear-leveled, so
memory wear is not a great concern – memory wear can
be compensated for by using a larger memory. For
example, for a given amount of data stored, a 1GB SD
card will last 10 times longer than a 100MB card.
This option is only available for the 28-pin device.
TQFP and SSOP packages are available, but they are
not in general distribution. Contact us for further
information.
Memory Integrity
With internal memory and 25AA1024 memory, power
loss during a write may result in corruption of data,
possibly requiring reformatting of the disk.
With external memory, power loss protection may or
may not be implemented by the memory itself.
If power is lost while a file is open, the file length
information in the directory entry may be incorrect, but
the data will be intact.
Application Circuits
The following circuits show a typical implementation of
the USB-FileSys. Suggested component values are
shown in table 3.
Table 3. Suggested component values
Label Component
R1-R3, R40-R44 22k resistor
R6 1k resistor
R21 470Ω resistor
T1 P-channel Mosfet, e.g. NDS352P
D1-D2 Low Vf switching diode
LED1 Light emitting diode
C1 1μF capacitor
C2, C3 22pF capacitor
C4, C6-C7 100nF capacitor
C8 470nF capacitor
X1 12MHz parallel cut crystal
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In figure 4, the internal memory is used. Vto is gated by
P-channel mosfet T1 to provide power take-off circuit,
for example to provide power to a battery charger.
Oscillator X1/C2/C3 may be replaced by a low-cost
resonator, provided its frequency tolerance is greater
than 0.25%. C1 and C6 should be placed close to the
USB connector. C7 should be placed near the Vss and
Vdd pins of the USB-FileSys and is required only if it
would be some distance from C6. C8 is a filter capacitor
for an internal regulator and is required.
The TEAclipper connector is for in-circuit programming
of devices where the firmware has been purchased from
HexWax. It is recommended to allow firmware updates,
even if the firmware is initially supplied pre-programmed.
LED1 is a USB activity indicator. The Sleep pin must be
biased high if unused.
Media/Vpp
PGD
Vdd
Vss
TEAclipper
connector 1 5
OSC1
OSC2
D+
Vusb
USB-FileSys
USB
C2
C3
X1
2 3 4
Vdd Vss
PGC
1
2
3
4
Vss
D-
Vss
C1
C6
C7
Vss
C8
Vdd
Vss
TxRx Vss
R21
MOSI-H
MISO-H
SCK-H
Sleep#
Host
MCU Vdd
Vss
Vcc
Gnd
MOSI
MISO
SCK
Slp#
R2
SSn-H SSn
SCK-M
USB-S
Vdd
Vto
T1
R1
R6
C4
PTO#
Vss
Vdd
R40
R44
LED1
Figure 4. Typical Application Circuit, Internal Memory
In figure 5, external memory is used. SW1 acts as a
media detect switch for an SD card. If 25AA1024
memory is used, the Media input should instead be
biased low; if non-removable SD memory is used, the
Media input should instead be biased high.
Media/Vpp
PGD
Vdd
Vss
TEAclipper
connector 1 5
OSC1
OSC2
D+
Vusb
USB-FileSys
USB
C2
C3
X1
2 3 4
Vdd Vss
PGC
1
2
3
4
Vss
D-
Vss
C1
C6
C7
Vss
C8
Vdd
Vss
TxRx Vss
R21
MOSI-H
MISO-H
SCK-H
Sleep#
Host
MCU Vdd
Vss
Vcc
Gnd
MOSI
MISO
SCK
Slp#
SSn-H SSn
MOSI-M
MISO-M
SCK-M
24AA1024
Serial
Memory
Vcc
Gnd
MOSI
MISO
SCK
SSn-M SSn
Vdd
Vss
USB-S
Vss
PTO#
Vbatt
Vdd
Vdd
R44
D1
D2
LED1
R3
Vdd
R40-R43
Vdd
Vdd
R2
SW1
Vdd
Vto
T1
R1
R6
C4
Figure 5. Typical Application Circuit, External Memory
D1 and D2 should have a very low forward voltage – ideally 0.3V.
In this implementation, two power sources are available:
power from the USB power input, and a battery Vbatt.
D1 and D2 ensure the higher of these is used to provide
the voltage Vdd. R3 ensures the USB-S power sense
signal is pulled low when the USB power is not present.
The USB voltage must be regulated to 3.3V if the serial
memory and/or host controller could not operate at 5V.
USB Connectors
Common USB connector and cable configurations are
shown in figure 6 and table 4. The shield on the
connector should be left unconnected. The ID pin on
the mini connector permits the distinction of A and B
plugs. The micro connector pin-out is the same as the
mini connector.
Figure 6 Common USB pin-outs for male connectors
Table 4. USB Connection Key
Pin
Std Mini Name Cable
color Description
1 1 Vcc Red +5V (can dip to 4.08V)
2 2 D– White Data –
3 3 D+ Green Data +
– 4 ID – Type A: Connect to ground
Type B: Not connected
4 5 Gnd Black Signal ground
For ultra-low cost products, it is possible to form a USB
Type-A plug direct from a circuit board as shown in
figure 6. This connector is only suitable for a limited
number of insertions (~50 before cleaning is required).
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It is unshielded and recommended only for ‘dongle’ type
products with no cables attached.
4. Vss
11.75
1.00-2.00
1.00
1.00
0.50
3.00
12.00
Shoulder required to prevent over-insertion
Overall PCB width 16.00 or less
Contacts plated with hard
gold flash (0.25-1.27µm)
over nickel (2.6-5.0µm)
Overall PCB thickness
including tracks 2.00 - 2.20
3. D+
2. D-
1. Vdd
2.25
1.25
Dimensions in mm
Figure 7. Integral USB connector dimensions
For further dimensional information, refer to figure 6-7 of
the USB 2.0 Specification, in the development kit.
SD Card Connector
The SPI connections for SD Cards is shown in figure 8.
The two pins marked BH are unused and must be
biased high.
6. Vss
2. MOSI
1. CS#
3. Vss
4. Vdd
5. SCK
7. MISO
8. BH
9. BH
Figure 8. SD Card Connections.
Pin 9 is out of order; this is not an error.
Host Commands
All commands start with a command byte and are
followed by a command-specific number of data bytes.
The response from USB-FileSys will start with a status
byte followed by a command-specific number of data
bytes. The response is then clocked out and must be
completely received before sending the next command.
For multi-byte values, the byte order is little-endian, i.e.
least significant byte first. While the response is being
clocked out, the value being clocked in must be 0xFF.
The possible status byte codes are shown in table 5.
Generally, USB-FileSys will respond with NOT_READY
while it computes a response, and then with the status
code resulting from the command. The host will have to
poll USB-FileSys repeatedly to determine the result. If
the result is anything other than SUCCESS, no further
data bytes will follow.
Table 5. Command Status Codes
Name Value Meaning
SUCCESS 0x00 Command successfully executed
NOT_POSSIBLE 0x01 Not possible to execute the command
as requested
FILE_NOT_FOUND 0x02 File not found
VOLUME_FULL 0x03 No empty clusters available
ENTRY_INVALID 0x05 File reference is not valid
Table 5. Command Status Codes
Name Value Meaning
HANDLE_IN_USE 0x06 File handle is in use
ROOT_DIR_FULL 0x07 Root directory is full. (The root
directory has a fixed size.)
OUT_OF_RANGE 0x08 Attempt to read after the last cluster
FAT_TABLE_ERROR 0x09 FAT table error
WRITE_FAILURE 0x0A Internal memory write failure
NOT_FORMATTED 0x0B Memory not formatted
NOT_MEMORY 0x0C Removable SD card not present
NOT_READY 0xFF Still computing result – try again later
In order to maximize the size of the available internal
memory, error checking is not exhaustively performed to
verify that the command sent to the host is legal. It is
the host’s responsibility to ensure commands are correct,
e.g. only deleting empty subdirectories and using legal
characters in file names.
A “current directory” is used to avoid long path names.
To open a file, it is necessary to move to that file’s
current directory first, and then open it.
When a file is opened, the host assigns a file handle
number (00-03), which is then used to refer to the file in
subsequent read and write commands. When the file is
closed, the file handle is freed to be used in another
open command.
Long file names are only partially supported. Full
support would significantly increase chip costs due to
patent licensing requirements. The PC may create files
and directories with long names, but they will only be
visible to USB-FileSys by their short file names. USB-
FileSys itself can only create files with short names, but
it can work with long-name files created by the PC by
referencing their short file name equivalents.
Short (“8.3”) file names are composed of a name of up
to eight ASCII characters followed by an extension of up
to three characters. If either the name or t he
extension are shorter than this, they should be padded
with spaces so that the file names is 11 characters long.
The following characters are not allowed:
1. Lower case letters ato z
2. Any of \ / : * ? " < > | + , . ; = [ ]
3. Control characters 0x00 – 0x1F
4. DEL character 0x7F
5. The first character must not be a space
Executing Commands While PC Connected
Executing commands while the PC is connected is
problematic, but possible.
USB-FileSys will ensure that the PC and the host do not
simultaneously modify the volume. Nevertheless, care
should be taken if the host modifies any files while the
device is connected to a PC.
In general the host and the PC should not attempt
modify the same file. It is recommended that the host
only modifies files whose directory entries have been
marked as read-only for the entire time that the PC has
been connected.
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Operating systems may cache data locally, and so
modifications made by the circuit may not necessarily
immediately apparent on the PC.
Sample Host Source Code
Sample C source code for host controllers is supplied in
the development kit. It was developed for the
PIC18F2320, but should be readily portable to other
microcontrollers. 28-pin PIC18F devices will fit in the
host controller socket in the evaluation board.
Root Dir
This command sets the current directory to the root
directory. The first byte of the command is the value
0x02. There are no further bytes. The response is the
status byte.
Example:
Command: Go to root directory.
02
Response: Success.
00
Get File Entry By Index
This command retrieves information about a directory
entry in the current directory. This could be a file, a
subdirectory, or a volume label. The first byte of the
command is the value 0x03. The second byte and third
bytes are the index number of the subdirectory or file in
the current directory being requested (least significant
byte first, zero-based).
The response will be the status byte and, if the status
byte is zero, the standard FAT directory entry data bytes
as shown in table 6. See the Set File Entry command
for an example.
Table 6. FAT directory entry
Byte Meaning
0-7 File name, padded with spaces
8-10 File extension, padded with spaces
11 Bit 0: Set if item is marked as read-only
Bit 1: Set if item is marked as hidden
Bit 2: Set if item is marked as a system file
Bit 3: Set if item is a volume label
Bit 4: Set if item is a subdirectory
Bit 5: Set if item is marked for archiving
If bits 0-3 all set, is an ignorable VFAT entry
12 Reserved
13-17 †Creation date / time:
Bits 0-7: Centisecond (1-199)
Bits 8-12: Doublesecond (0-29)
Bits 13-18: Minute (0-59)
Bits 19-23: Hour (0-23)
Bits 24-28: Date (1-31)
Bits 29-32: Month (1-12)
Bits 33-39: Year since 1980 (0-127 = 1980-2107)
18-19 ‡Date of last access:
Bits 0-4: Date (1-31)
Bits 5-8: Month (1-12)
Bits 9-15: Year since 1980 (0-127 = 1980-2107)
20-21 Reserved
Table 6. FAT directory entry
Byte Meaning
22-25 Last modified date / time:
Bits 0-4: Doublesecond (0-29)
Bits 5-10: Minute (0-59)
Bits 11-15: Hour (0-23)
Bits 16-20: Date (1-31)
Bits 21-24: Month (1-12)
Bits 25-31: Year since 1980 (0-127 = 1980-2107)
26-27 Reserved
28-31 File length in bytes, LSB first
†Supported by USB-FileSys except centiseconds
‡ Supported by USB-FileSys in certain cases, see Close command
Get File Entry By Short Name
Same as Get File Entry command, except searches for
a file that matches the name and attributes supplied.
The first byte of the command is the value 0x04. The
next 8 bytes are the file name, padded with spaces.
The next 3 bytes are the file extension, padded with
spaces. Last is the attribute byte, usually 0x00 for a file,
0x10 for a subdirectory, or 0x08 for the volume label, as
specified by byte 11 of table 6. (Only the volume label
and subdirectory bits are used when searching for a file.
Other bytes are only used if a non-existent file is then
created using the Open command.)
For examples, see the Change Dir and Open
commands.
Change Dir
This command sets the current directory to the file
returned by the immediately preceding Get File Entry By
Index or Get File Entry By Short Name command. This
last file must be a subdirectory; it cannot be the “..”
pointer to the parent directory. The command consists
of the byte 0x05 only. The response is the status byte.
Example:
Command: Find subdirectory “DATA”.
04 44 41 54 41 20 20 20 20 20 20 20 10
Response: Success.
00 44 41 54 41 20 20 20 20 20 20 20 10…
Command: Move to the subdirectory.
05
Response: Success.
00
Set File Entry
This command sets directory entry of the file returned by
the immediately preceding Get File Entry By Index or
Get File Entry By Short Name command. The one-byte
the command is the value 0x06. A response byte will be
received. Assuming this the Success response 0x00,
the 32 file entry data bytes are then sent, as specified in
table 6. (The bytes market reserved must be left
unchanged.) A second response byte will then be
received.
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Example:
Command: What is the 5th directory entry in the
current directory?
03 04 00
Response: Success, file is a read-only file called
“FRED.TXT”.
00 46 52 45 44 20 20 20 20 54 58 54 01…
Command: Set file entry
06
Response: Success.
00
Data: (Renamed “TOM.TXT”)
00 54 4F 4D 20 20 20 20 20 54 58 54 01…
Response: Success.
00
Example:
Delete File / Directory
This command deletes the file, subdirectory or volume
label retrieved by the last Get File Entry By Index or Get
File Entry By Short Name command. The first byte of
the command is the value 0x07 followed by the
confirmation bytes 0x59, 0x65, 0x73 (“yes”).
The response will be the status byte.
Example:
Command: What is the 5th directory entry in the
current directory?
03 04 00
Response: Success, file is a read-only file called
“FRED.TXT”
00 46 52 45 44 20 20 20 20 54 58 54 01…
Command: Delete it
07 79 65 73
Response: Success.
00
Only empty subdirectories should be deleted; it the
host’s responsibility to delete all directory entries first.
(The “.” and “..”entries do not need to be deleted.)
Format Volume
This command deletes the entire contents of the internal
volume or the 25AA1024 external memory. It frees up
any clusters which may have been rendered unusable
due to deletion of a non-empty directory or power failure
during a file operation. The root directory will become
the current directory.
The first byte of the command is the value 0x08 followed
by the confirmation bytes 0x59, 0x45, 0x53 (“YES”).
The response will be the status byte.
SD memories must be formatted by the PC. 24AA1024
memories can be formatted by the PC when used with
the 28-pin USB-FileSys.
20-pin devices should only format using the Format
Volume command.
Example:
Command: Format volume
08 59 45 53
Response: Success.
00
Set Date / Time
This command sets the date and time as used by file
creation and file close commands. It does not keep time.
This command should be given immediately before the
open command when a file is being created and all
close commands. If the command is never given, files
are given the date / time 12:00 1/1/2000 when created
and left unchanged otherwise.
The first byte of the command is the value 0x09. The
following four bytes indicate the date and time as shown
in table 7.
Example:
Command: Set date / time to 12:00, 1/1/2000
09 00 60 21 28
Response: Success.
00
Table 7. Date / time structure
Byte Meaning
0-1 Time:
Bits 0-4: Doublesecond (0-29)
Bits 5-10: Minute (0-59)
Bits 11-15: Hour (0-23)
2-3 Date:
Bits 0-4: Date (1-31)
Bits 5-8: Month (1-12)
Bits 9-15: Year since 1980 (0-127 = 1980-2107)
Open File
This command opens an existing file, or creates it if it
does not exist already, using information from the
previous Get File Entry By Index or Get File Entry By
Short Name command. The first byte of the command
is the value 0x0A. The second is the “file handle” to
associate with the file, which can be a value from 00 to
03. The response will be the status byte. The file must
be closed before the file handle is re-used.
The Open command may be used for creating a
subdirectory or volume label. In this case, the directory
entry is created but no file is opened and the file handle
is ignored. In the case of a subdirectory, the current
directory is changed to the new subdirectory.
It is permitted to open a file more than once
simultaneously, for example to copy data from one
section of the file to another, provided only one file
handle is used for writing to the file.
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Files can only be created after using the Get File Entry
By Short Name command.
Example 1 (open existing file):
Command: What is the 5th directory entry in the
current directory?
03 04 00
Response: Success, file is a read-only file called
“FRED.TXT”
00 46 52 45 44 20 20 20 20 54 58 54 01…
Command: Open the file using handle 01
0A 01
Response: Success, file is open on handle 01
00
Example 2 (create file):
Command: Find file “FRED.TXT” (note the read-only
attribute is set, although this is ignored
while searching for the file)
04 44 41 54 41 20 20 20 20 20 20 20 01
Response: Fail, file does not exist.
02
Command: Create the file as read-only using handle
03
0A 03
Response: Success, file is open on handle 01
00
Example 3 (create subdirectory):
Command: Find subdirectory “DATA”.
04 44 41 54 41 20 20 20 20 20 20 20 10
Response: Fail, file does not exist.
02
Command: Create subdirectory (file handle ignored)
0A 00
Response: Success. (No file is opened)
00
Close File
This command closes the file associated with a file
handle. The first byte of the command is the value 0x0B.
The second is the “file handle” of the open file. The next
four bytes (LSB first) are the desired length of the file, or
0xFFFFFFFF if the length is to be the ‘expected length’.
The expected length is greater of the length recorded in
the directory entry and the highest position written to
while open.
The main effect of this command is to update the length
argument in the directory entry and, if it was shortened,
to free any unused clusters at the end of the file.
If external memory is used, the creation, modify and
access date/time are all fully updated as required. If
internal memory is used, these fields will only be
updated by USB-FileSys if the directory entry would
have been modified anyway. (i.e. When the file is
created and when it is closed with a different length than
when it was opened.)
Example 1:
Command: Close file handle 02 with expected length
0B 02 FF FF FF FF
Response: Success
00
Read File
This command reads data from a file starting from the
file pointer position. The first byte of the command is
the value 0x0D. The second is the “file handle” of the
open file. The next four bytes are the position in the file
to read from, or 0xFFFFFFFF to continue on
sequentially from the last read or write command. (If
there have been no previous read or write command,
the start of the file will be assumed.)
With the 28-pin device, the next two bytes are the
number of bytes to read, up to a maximum of 512. The
read must not cross the 512-byte sector boundary.
With the 20-pin device, the next two bytes are the
number of bytes to read, up to a maximum of 64. The
read must not cross the 64-byte page boundary.
Note: The file length information in the directory is
ignored. The data may be read up to the last cluster
itemized in the file allocation table.
The response will be the status byte followed by the
data bytes read.
Example:
Command: Read 4 bytes at position 0123 from file
handle 02
0D 02 23 01 00 00 04 00
Response: Success, data is 12 34 56 78.
00 12 34 56 78
Write File
This command writes data to a file starting from the file
pointer position. The first byte of the command is the
value 0x0E. The second is the “file handle” of the open
file. The next four bytes are the position in the file to
write to, 0xFFFFFFFE to append onto the end of the file,
or 0xFFFFFFFF to continue on sequentially from the last
read or write command. (If there have been no previous
read or write commands, the start of the file will be
assumed.)
With the 28-pin device, the next two bytes are the
number of bytes to write, up to a maximum of 512. The
write must not cross the 512-byte sector boundary.
p9 of 10 26-Aug-10 USB-FileSys / USB-Config HW149-8 www.hexwax.com
With the 20-pin device, the next two bytes are the
number of bytes to write, up to a maximum of 64. The
write must not cross the 64-byte sector boundary.
Once the command has been sent, a response byte will
be received. Assuming this the Success response 0x00,
the data bytes are then sent. A second response byte
will then be received.
Note: Writes to files are permitted even if the read-only
bit is set in their directory entry; writes after the end of
the existing file may cause further clusters to be
allocated to the file.
Example:
Command: Write 4 bytes at position 0123 on file
handle 02
0E 02 23 01 00 00 04 00
Response: Success, data is 12 34 56 78.
00
Data: (01 02 03 04)
01 02 03 04
Response: Success.
00
Get Info
This command reads device information. The command
is the byte 0x0F. The first byte of the response is the
status byte. The second bytes indicates the information
in table 8. The third and fourth bytes are the version
number, least significant byte first.
Example:
Command: Get Info
0F
Response: Success, device is 500mA with a 4096-
byte cluster size, version 0001
00 61 01 00
Table 8. Info Flags
Bit Meaning
0Maximum current draw:
0: Draw a maximum of 100mA from USB (default)
1: Draw a maximum of 500mA from USB
2-1 Activity pin function:
00: High for 100ms on any USB activity
10: High on PC write to any sector
11: High on PC write to root directory entry
5-7 Cluster size:
000 - 512 bytes
001 - 1024 bytes
010 - 2048 bytes
011 - 4096 bytes
100 - 8192 bytes
101 - 16384 bytes
110 - 32768 bytes
(Read only – ignored with Set Info command)
Set Info
This command sets the maximum current the device
may draw from the PC, and the function of the Activity
pin. The first byte of the command is the value 0x10.
The second is as specified in table 8. The response is
the status byte.
If USB-FileSys is configured for 500mA current draw, it
will only work when plugged directly into PCs and
powered hubs. The setting takes effect from the next
plug-in. In any event, the no more than 100μA should
be drawn if the PTO# pin is high.
Example:
Command: Set 500mA operation, activity on write
10 05
Response: Success.
00
Delivery and Programming
USB-FileSys is generally distributed in pre-programmed
in 28-pin DIL and 20-pin SSOP packages. Contact us
for other package options.
In high volumes (5K+), USB-FileSys is available reeled
with your custom settings preloaded, in any available
package.
TEAclipper Programming
For programming the firmware using TEAclipper/PIC HV,
the PGC, PGD and Vpp pins must be accessible.
During programming, these pins must be protected
against contention. In particular, note that Vpp is
subject to up to 13V during programming. Nothing else
should be connected to Vpp except via a 22k pull-up
resistor.
The TEAclipper connector format is shown in figure 9.
Since the programming time is very fast, no
programming socket is required. The TEAclipper can be
‘leaned’ against the plate-through holes shown.
It is strongly recommended that this connector is
included in circuits even if in-circuit programming is not
anticipated, since this allows you to upgrade the
firmware if necessary.
1mm hole dia
2.54mm spacing
Pin 1 indicated
by square pad
PGD
PGC
Vpp
Vss
Vdd
Figure 9. Recommended plate-through connector design
Evaluation Board
The USB-Eval evaluation board is available for
evaluating USB-FileSys. Due to the variety of potential
implementations it is supplied unpopulated and a
prototyping area is provided. This will be necessary for
SD memory implementation. (e.g. Figure 10.)
p10 of 10 26-Aug-10 USB-FileSys / USB-Config HW149-8 www.hexwax.com
It is recommended that new users initially try to replicate
figure 4 and then modify it to test the circuit they actually
require. Note the following common omissions:
1. The Sleep pin must be biased high if unused.
2. SD memory will need 3.3V power regulation.
You may be interested in using disk sector analysis
software such as Disk Investigator, which can be
downloaded free from www.theabsolute.net.
Figure 10. Evaluation board example
Development Kit
A firmware development kit is available for download
from www.hexwax.com containing the following files:
This data sheet.
Sample host controller source code.
Base controller data sheets (© Microchip
Technology Inc)
USB 2.0 Specification (© HP / Intel / Lucent /
Microsoft / NEC / Philips 2000)
The FAT File System. (Wikipedia article.)
Revision history
The following limitations exist with rev 0001 DIL parts.
(All SS parts are rev 0002 or higher.)
Files should not be truncated to length zero.
If when a file is created, it should be immediately
closed and reopened prior to writing or reading.
Info flags reported by Get Info command are
meaningless.
Read command returns the correct only if a write
command was sent more recently than a close
command.
Cannot add cluster to a FAT16 file from the SPI
host. There is no easy workaround, so contact us
for an upgrade if you need this capability.
25AA1024 memory must be formatted from the PC.
Warranty
The warranty and liability provisions for this pre-loaded software product
follow software industry conventions. Please refer to www.hexwax.com
and/or www.flexipanel.com for a complete warranty statement.
