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ADS1299 Daisy Chain with TI Sitara Processor

Ravindra
Intellectual 870 points
Other Parts Discussed in Thread: ADS1299

All,

We are trying to daisy-chain 3 ADS1299 Chipsets connected over SPI3 Bus to a TI Sitara Processor. Our SPI Register configurations are shown below:

[  155.864568] speed_hz = 12000000,div = 2
[  155.868755] bytes_per_word = 4
[  155.872188] cs->word_len = 24
[  155.875351] disable fifo : 1
[  155.878417] mcspi registers .....
[  155.882158] CH0CONF = 6161bc9
[  155.885320] CH0STAT = 6
[  155.887924] MCSPI_XFERLEVEL = 200
[  155.891655] CH0CTRL = 0
[  155.894261] SYSSTS = 1
[  155.896774] modulctrl = 1
[  155.899564] syst = 0
[  155.902118] mcspi registers .....
[  155.905655] CH0CONF = 16161bc9
[  155.908907] CH0STAT = 26
[  155.911792] MCSPI_XFERLEVEL = 200
[  155.915325] CH0CTRL = 0
[  155.917930] SYSSTS = 1
[  155.920440] modulctrl = 1
[  155.923457] syst = 0

We are configuring the SPI3 Clock to 12 Mhz and are trying to capture the Data from the 3 Daisy-chained ADS1299 using the EDMA Channels. We are able to capture the data only from the 2nd and the 3rd chip and the data coming from the 1st chip is completely lost. When we put the ADS1299 in Test/Input Shorted Mode, we are seeing the below data:

[   37.879020] c00000   142eb   14298   14248   142f5   14312   1438a   142c9   14416
[   37.885914] c00000   14319   1423b   1421f   142af   14299   142cc   1438a   1438a
[   37.892785] 1438a    1438a   1438a   1438a   1438a   1438a   1438a   1438a   1438a

The first 0xC00000 is from the 2nd Chip and the second 0xc00000 is from the 3rd chip. Any suggestions/pointers to look out for. When we probed the SPI Lines using oscilloscope, we are able to see the data from all the 3 chips. I have attached the screen shot here for reference.

Thanks,
Ravindra

  • 0
    TI__Mastermind 38745 points
    Hey Ravindra,

    I moved your post to the Sitara Forum because it sounds like you are not having trouble with the ADS1299 specifically.

    Some background on the ADS1299 for Sitara engineers: the ADS1299 is a 8-channel, 24-bit, simultaneous sampling ADC used for biopotential applications. It has a SPI-compatible, daisy-chainable interface in which for one device, you should expect 24 bits of status (always begins with 0xC0) and 8 channels x 24 bits. In the scenario this community member is describing, they expect 3 devices worth of data; or a total of 81 bytes per collection.

    Regards,

    Brian Pisani
    Precision Delta Sigma ADCs