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TM4C1294NCPDT: SPI communication issue between TM4C1294NCPT with ADS1220

user5266678
Prodigy 30 points
Part Number: TM4C1294NCPDT
Other Parts Discussed in Thread: ADS1220

I am designing in TM4C1294NCPDT which communicate with ADC chip ADS1220 via SPI interface. ADS1220 is 24 bits sigma-delta AD converter, and employs 24bit spi interface. In order to read ADC result via SPI interface, TM4C1294NCPDT need config QSSI  as SPI mode. But this microcontroller is 16 bits SPI , it seems that this SPI is not incompatible with ADS1220 SPI. So I don't know how to solve this issue. These two chips are TI's product, and I think there is good solution provided by TI. If demo example can be showed, it is ok for me to process project. thanks.

  • 0
    TI__Guru*** 135355 points
    Hello,

    Welcome to the E2E forums!

    I reviewed the ADS1220 datasheet, but I am not seeing a specific requirement on SPI interface to send 24-bit data packets. It looks like the standard data size is 1 byte or 8 bits, and then from there you can send multiple bytes per transaction. The SPI bus for the TM4C1294NCPDT will therefore be able to support that as it can certainly transmit multiple bytes of data in a single communication cycle. I do believe that the ADS1220 will want Slave Select to stay low throughout the transfer though, and due to that I believe you will need to "manually" control SS rather than allow the SPI peripheral to control SS for you. This way you can pull SS low prior to SPI transaction, send or receive the multiple bytes of data, and then drive SS high after the transaction is done. That should allow you full SPI communication with the ADS1220.

    Unfortunately, we don't have a demo example or project for that ADC. While it is another TI part, we simply make way way too many devices to have SPI examples for all of them. I would recommend you start building from the SPI examples provided from our TivaWare Software. You can find SPI examples in the following location after downloading TivaWare: [Install Path]\TivaWare_C_Series-2.1.4.178\examples\peripherals\ssi

    You may also check with the ADS1220 group what example software they would recommend for starting with their device on their end as well. It may not be with a TM4C MCU (looks they did many TI Designs with MSP430's from what I can see on their Tools and Software page), but that would be another good resource to leverage if they can provide it because then you can see what the communication requirements are for the device and then adapt our TivaWare drivers to replicate the required sequences.
  • 0 in reply to Ralph Jacobi
    Guru 117855 points

    It may be wise to note - as well - that ANY 24 bit ADC presents a "serious" physical design, implementation challenge.     "Breadboards "NEED NOT" apply - proper pcb layout proves mandatory - and NO high-frequency or "rapid-edged" switching signals should come "near" - so precision a device."

    The supply power and reference to such a device must be (very much) "to spec" - for (anywhere near) that 24 bit promise to be achieved...

    It is hoped that an "Official Eval Board" is available for such device - "beginner or early user attempts" - to implement such a device - are not "famed" for their "success!"