PmodAD2TM Reference Manual Revision: August 30, 2011 Note: This document applies to REV A of the board. 1300 NE Henley Court, Suite 3 Pullman, WA 99163 (509) 334 6306 Voice | (509) 334 6300 Fax Overview The PmodAD2 is an analog-to-digital converter module with up to four channels at 12-bit resolution powered by the Analog Devices AD7991. Features include: * * * * * up to four analog to digital converter channels up to 12-bit resolution on-board 2.048V voltage reference ability to choose the voltage reference I2C interface Functional Description The PmodAD2 uses an 8-pin connector that allows communication via I2C. The PmodAD2 also has a 6-pin connector that allows up to four analog inputs or up to three analog inputs and a voltage reference. Interface All communications with the device must specify a device address and a flag indicating whether the communication is a read or a write. This is followed by the actual data transfer. For details on read and write procedures please see the AD7991 datasheet. Interface Connector Signal Description Connector J1 - I2C Communications Pin Signal Description 1, 2 SCL I2C Clock 3, 4 SDA I2C Data 5, 6 GND Power Supply Ground 7, 8 VCC Power Supply (3.3V) The I2C interface standard uses two signal lines. These are I2C data (SDA) and I2C clock (SCL). These signals map to the serial data (SDA) and serial clock (SCL), respectively, on the AD7991. Device configuration is performed by writing to the configuration register within the device. This allows you to choose which channels are converting data, whether or not there is an external reference voltage, and whether or not there is bit trial or sample delay. To read data from the conversion result, see "Reading from the AD7991/AD7995/AD7999" in the AD7991 datasheet. Doc: 502-217 page 1 of 2 Copyright Digilent, Inc. All rights reserved. Other product and company names mentioned may be trademarks of their respective owners. PmodAD2 Reference Manual Analog Inputs and VRef The PmodAD2 allows for up to four analog inputs, VIN1 - VIN4. To use the input VIN4, the jumper JP1 must be set to V4. The configuration register has a REF_SEL bit that, when enabled, allows a voltage other than the supply voltage to be used as the reference. If REF_SEL is enabled, and if JP1 is set to REF, VRef from the on-board voltage reference generator is 2.048V. If JP1 is set to V4, VRef is the voltage at input VIN4. Connector J2 - Analog Input Pin Signal Description 1 VIN1 Analog Input 1 2 VIN2 Analog Input 2 3 VIN3 Analog Input 3 4 VIN4 Analog Input 4 5 GND Power Supply Ground 6 VCC Power Supply (3.3V) www.digilentinc.com page 2 of 2 Copyright Digilent, Inc. All rights reserved. Other product and company names mentioned may be trademarks of their respective owners.