ADS131M08: Unable to change word-size to 16 bit or 32 bit for communication with MSP432P401R

Part Number: ADS131M08
Other Parts Discussed in Thread: MSP432P401R,

Hi all,

We are communicating AFE IC 131M08 with MSP432P401R.

We want to set data word length to 16 bit. It can be set by writing to Mode register value 0x0410. ( MSB first 0x04 & then LSB 0x10)

STATUS register(is a only readable register) which updates the configuration done on AFE device.

We checked waveform of STATUS reg, & decoded, data word length is always set to 24bits.

Kindly help.

The sequence for writing to MODE reg is as follows:-

As per AFE data sheet Wreg Command is 011a aaaa annn nnnn

Where a aaaa a is address of register to be written, nnn nnnn is the actual no. of registers to be written minus one.

The address of Mode Register is 02h. Accordingly our command was

0110 0001 0000 0000 i.e 0x6100

Also our data in register was 0x0410.

So entire Data frame was: 0x61,0x00,0x00,0x04,0x10,0x00,0x00

The waveform for mode reg is 

Where first 3 bytes from left are command word. As by default word size is 24 bit, command is Zero padded followed by data to be written to register followerd by Zero padded CRC(as input CRC is disabled).


Thanks & Regards

  • We are facing difficulty in configuring Mode register of ADS131M08. We are using SPI with MSB first configuration.
    As per datasheet, for writing a Register the following command is to be sent, 011a aaaa annn nnnn.
    Where, a aaaa a is the address of register,
                 nnn nnnn is the actual no. of registers to be written minus 1. 
    In case of configuring MODE register, its address is 02h and we are writing a single register so, a aaaa a is 0 0001 0 and nnn nnnn is 000 0000.
    As a result the entire command is 0110 0001 0000 0000 (6100h).
    To send it over SPI as a frame the command will be (considering 24 Bit word size of AFE as default)
    0110 0001 0000 0000 0000 0000 0000 0100 0001 0000 0000 0000 0000 0000 0000 0000 0000 0000. 
    Where Command is shown in Red, register Data in Green and CRC in Blue. (Eight Bits of Zero are padded to maintain 24 bit word size. Also since input CRC is disabled Zero padding is done in place of CRC as per Datasheet.)
    With this command we intend to change the AFE word size to 16 bit, however the AFE bit size is not changing. We checked waveform for the same. Word size is always getting set to 24 bits only.
    We used same sequence to send commands to modify CLOCK register. Its address is 03h and could change OSR Values as desired.
    The command to set OSR 2048 is 0110 0001 1000 0000 0000 0000 1111 1111 0001 0010 0000 0000 0000 0000 0000 0000 0000 0000
    We can see from the waveform OSR is set to 2048, as ADC cycle set to 500usec.
    Similarly to set OSR to 1024 command sent is 0110 0001 1000 0000 0000 0000 1111 1111 0000 1110 0000 0000 0000 0000 0000 0000 0000 0000
    We can see from the waveform OSR is set to 1024, as ADC cycle set to 250usec.
  • Hello,

    Thank you for your post.

    The DIN sequence shown in your scope capture does not appear to match the data frame you intended to send. It looks like you are sending:

    0x05 0x10

    Can you show the complete SPI frame? Also, are you able to check the response of the WREG command in the next frame? This will also confirm whether the device is properly recognizing the command.


  • Thanks for your reply.

    Yes, you are correct its 0x05 0x10

    But, the image shown is response when we read MODE reg. So it is set to 24 bit always. 

    Thanks & Regards