ADS112C04: How to read the data from each channel in the ADS112C04

Hi Nareshreddy,

The ADS112C04 does not have an auto-scan feature nor is there a FIFO memory.  Each input channel must:

• first be selected,
• the end of conversion detected,
• and the conversion data read from the device. 

This action is required for each input channel desired. 

Best regards,

Bob B

Hi Nareshreddy,

I would refer you to the ADS112C04 datasheet for details regarding continuous conversion and single-shot modes of operation.  Basically continuous mode refers to continuous conversions of the selected mux channel.  Once a conversion completes another conversion is started automatically.  For single-shot mode only one conversion for the selected mux channel completes and then the ADS112C04 will go to a low-power state.

Best regards,

Bob B

Hi Nareshreddy,

I explained this process previously and will attempt to do so again with a little more detail.  I assume that when you say you want to measure AIN0 you really want to measure AIN0 to AVSS as the mux selection.  For this discussion we will use the default register settings for all but register 0.  To make single-ended measurements referenced to AVSS (AGND) you need to disable and bypass the PGA (bit 0 should be set to 1) in register 0.

• AINP= AIN0 and AINN= AVSS must first be selected in configuration register 0.  The mux selection bits (MUX[3:0]) are bits 7-4 of register 0.  AIN0 to AVSS is 1000b and the value for register 0 would be 10000001b or 0x81.  You need to send the WREG command for register 0 which would be 0x40 0x81
• Write the START command 0x08
• Monitoring DRDY going from high to low state,
• and the conversion data read from the device using the RDATA command by writing 0x10 then reading 2 bytes of data. 

You would repeat this process for the other channels:

• Set the mux to AIN1 by WREG 0x40 0x91
• Set the mux to AIN2 by WREG 0x40 0xA1
• Set the mux to AIN3 by WREG 0x40 0xB1

Please review the ADS112C04 datasheet for specific details on how to accomplish the various operations.

Best regards,

Bob B

Hi Nareshreddy,

Although you can operate in continuous conversion mode, it may be easier to keep the conversions from overlapping if you use the single-shot mode instead.  In continuous conversion mode writing a new mux configuration will restart the conversion with the new configuration, but using this mode you will need to make sure that you keep track of the conversions and the time they are ready to read.

In single-shot mode you control when you want to start the conversion as well as when you want to read the result.  In this way it is a little easier to program the loop.

In pseudo code with single-shot mode the code flow would appear something like:

While (.t.)

{

1. Send the WREG command to set the mux to AIN0-AVSS
2. Send the Start command to start the conversion for AIN0
3. While loop for DRDY high and exit the loop when DRDY goes low
4. Issue the RDATA command and read the result for AIN0
5. Send the WREG command to set the mux to AIN1-AVSS
6. Send the Start command to start the conversion for AIN1
7. While loop for DRDY high and exit the loop when DRDY goes low
8. Issue the RDATA command and read the result for AIN1
9. Send the WREG command to set the mux to AIN2-AVSS
10. Send the Start command to start the conversion for AIN2
11. While loop for DRDY high and exit the loop when DRDY goes low
12. Issue the RDATA command and read the result for AIN2
13. Send the WREG command to set the mux to AIN3-AVSS
14. Send the Start command to start the conversion for AIN3
15. While loop for DRDY high and exit the loop when DRDY goes low
16. Issue the RDATA command and read the result for AIN3
17. Loop back to beginning (1)

}

That is the basic flow.  There are some variations that can be done to speed the loop up, but this single-shot mode works well for making sure that every conversion is read at the proper time.

Best regards,

Bob B

Hi Nareshreddy,

I can see now why this may be a bit confusing.  There are I2C communication S (start condition of I2C communication), Sr (repeated start for I2C communication) and P (stop condition for I2C communication).

There are also commands for the ADS112C04 itself that include the START/SYNC command (which will start conversions in single-shot mode or restart conversions in continuous mode), the WREG (write the ADC register), the RREG (read the ADC register) and the RDATA command (read the last completed conversion result).

Each of the ADC commands must be framed by the I2C communication.  For example:

<S> 0x80 0x40 0x81 <P>  // WREG command to set the mux

<S> 0x80 0x08 <P>           // ADC START/SYNC conversion command

Monitor DRDY and wait for DRDY to transition from high to low

<S> 0x80 0x10 <Sr> 0x81 {MSB byte} {LSB Byte} <P>  // RDATA command and data returned from ADC

I hope that makes it a little more clear.

Best regards,

Bob B