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ADS1110: I2C "silences"

René BRUNIER
Prodigy 30 points
Part Number: ADS1110

Hi There,

Question regarding ADS1110.
I'm using default settings (Gain=1, 15 SPS, continuous-conversion mode)

I'm experiencing I2C silences :
The I2C interface is interrogated every second. The software does the following:
1) write Configuration register with 8C (hex).
2) loop for up to 5 reties to get output register content (2 bytes output register + 1 byte configuration register), exit the loop as soon as a response is provided by slave (3 bytes received).

What i'm experiencing:
- the write in configuration register is not always accepted (going deep into I2C signals, there is not ACK from ADS1110 after writing slave address)

- the read from output register does always provides a response and there is nothing wrong in I2C frame, just no response.

Questions:
- Is it correct to set configuration register on periodic basis and especially just before reading output register ?

- is this normal to not have response from device from time to time.

- is there a bad time or good time to read the output register ? I mean, when the conversion is over, and the register is updated, is it the good moment to read or is there some kind of interlock preventing to read partially updated data ?
Just wondering if i need to 'sync' output register reading with conversion and if so , how ?

thanks for support
Best regards

René

  • 0
    TI__Mastermind 24970 points

    Hello René,

    1. it is not necessary to write to the configuration register each time you want to read the output register. the configuration register should be written after power up, to set the device to the desired configuration. after that, it should only be written to if the configuration needs to be changed. In continuous mode, there is not much need to write to this anymore. In single conversion mode, it will need to be written to start a new conversion. 

    2. It is not normal to have the device not acknowledge the host device, the device should respond with an acknowledge if addressed correctly. aside from this, there may be times when the device will not execute a command, for example, when writing a 1 to ST/DRDY while a conversion is in progress has no effect. 

    3. There is no bad time to read the output register, it is possible to ignore the ST/DRDY bit and read data from the ADS1110’s output register at any time, without regard
    to whether a new conversion is complete. If the output register is read more than once during a conversion cycle, it will return the same data each time.   In continuous-conversion mode, use ST/DRDY to  determine when new conversion data is ready. If ST/DRDY is 1, the data in the output register has already been read, and is not new. If it is 0, the data in the output register is new, and has not yet been read.

    Regards

    Cynthia