Connecting I2C based ADC to Raspberry Pi

Question

I have ADS7828E,MCP3221A5T ADC ICs with me. I am interested to know

1. Is these devices can work with raspberry pi? I want to connect ADC using I2C interface.

2. The steps I should take to run ADC using I2C.

I am adding some of the features of these ADCs.

MCP3221:

1. 12-bit resolution
2. ±1 LSB DNL, ±2 LSB INL max.
3. 250 μA max conversion current
4. 5 nA typical standby current, 1 μA max.
5. I2CTM-compatible serial interface
   • 100 kHz I2C Standard Mode
   • 400 kHz I2C Fast Mode
6. Up to 8 devices on a single 2-Wire bus
7. 22.3 ksps in I2C Fast Mode
8. Single-ended analog input channel
9. On-chip sample and hold
10. On-chip conversion clock
11. Single-supply specified operation: 2.7V to 5.5V
12. Temperature range:
    • Industrial: -40°C to +85°C
    • Extended: -40°C to +125°C

ADS7828:

1. 8-CHANNEL MULTIPLEXER
2. 50kHz SAMPLING RATE
3. NO MISSING CODES
4. 2.7V TO 5V OPERATION
5. INTERNAL 2.5V REFERENCE
6. I2C INTERFACE SUPPORTS: Standard, Fast, and High-Speed Modes

I am using raspberry pi with 18-09-2012 image.

Could you help me?

Answer 1

The A/D devices' voltage range is within the Raspberry Pi's operating voltage. You should use this instructable to setup I2C communication on your Raspberry Pi. The AD 7828's datasheet provides information on how to read the data from the A/D converter. You may have to add an external voltage reference if necessary (The datasheet have some information)

You should do it in the following sequence:

1. Set read address on I2C interface
2. Send read command.
3. Read incoming data.

Sometimes, the i2c modules may have to be added manually by:

sudo modprobe i2c-bcm2708

You can use the overo-blinkm example to tweak and use it to your needs.