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ADS131M04: Using External CLK

Aniruddha Mukherjee
Prodigy 100 points
Part Number: ADS131M04


Hi

We are using the ADS131M04EVM with a TI c2000 launchpad. We are able to communicate with the device and configure the ADS131M04 registers when using a clock from the DSP and the CLK is applied after the register figuration. But if we try to use the Onboard 8.192MHz Oscillator, the ADC will have CLK all the time but doesn't allow  its registers to be configured. Is it possible to configure the ADS131M04's registers while its getting a CLK input?

thanks

Aniruddha   

  • 0
    TI__Guru 66906 points

    Hello Aniruddha,

    Thank you for your post.

    I'm surprised to hear that register read/write is working without a clock. After the clock is provided by the DSP, are you able to confirm that the registers retained the written values?

    For normal operation, it is expected that the master clock input is always applied. 

    Regards,

    **Edited 11/19/20 - registers can be read and written without a master clock input **

  • 0 in reply to Ryan Andrews
    Prodigy 100 points

    yea and that's how its done in the energy meter reference design. The the code is based on TI reference design SW that I got from TI application engineering. 

    Line 150 in setup.c

    PMAP_configurePorts((const uint8_t *) Sensing_Disabled, ADS131M04_PORT_MAP, 1, PMAP_ENABLE_RECONFIGURATION);

     

    and line 815 in adc_commands.c:

    PMAP_configurePorts((const uint8_t *) Sensing_Enabled, ADS131M04_PORT_MAP, 1, PMAP_ENABLE_RECONFIGURATION);  

     

    I don’t have the code for PMAP_configurePorts since it’s a part of chip support library for that ARM microcontroller.

    The reference app is calling that function with Sensing_Disabled right before writing to ADC registers and again with Sensing_Enabled right after the writes are done.

    That parameter defines a port map that enables/disables clock signal.

  • 0 in reply to Aniruddha Mukherjee
    TI__Guru 66906 points

    Hi Aniruddha,

    I've just edited my initial reply after I verified that the register can be written and read without the master clock input. Sorry for the confusion.

    Can you capture the SPI signals and also the master CLKIN signal with a scope or logic analyzer? Perhaps we can review the communication for a single register write and read back to validate the expected responses are received.

    Regards,

  • 0 in reply to Ryan Andrews
    Prodigy 100 points

    Currently the main issue we have is that, if we apply the CLKIN from startup before the registers are configured, we cannot configure the registers we can still read it and the ADC runs with its default setting.

    Is that normal ?

     Also, is their a way to configure the ADC with CLKIN from startup?

  • 0 in reply to Aniruddha Mukherjee
    TI__Guru 66906 points

    What is the response if you only send the NULL command? This should show the contents of the STATUS register in the next frame.

  • 0 in reply to Ryan Andrews
    TI__Guru 66906 points

    One more point - the /DRDY pin will transition from low to high after the internal POR (power-on reset) has completed. This indicates that the device is ready to accept SPI commands. Are you monitoring this pin and waiting for the low-to-high transition before communicating with the device?

    Regards,