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SSI Mode

Shubham Arora
Intellectual 520 points
Other Parts Discussed in Thread: TM4C123GH6PGE, ADS1218

HI

I am writing code for mulitple slave on TIVA TM4C123G board  ,wherein TIVA would act as master .

So i didn't want to use SSI Fss pin . can i configure this pin as gpio output pin ?

and now since i m not using Fss what mode should i operate among these : Texas Instruments synchronous serial,Freescale SPI Format , MICROWIRE Frame Format ?

  • 0
    TI__Guru**** 244400 points

    Hello Shubham,

    Yes you can configure the FSS pin as a GPIO output pin.

    Secondly FSS is Chip Select. It has no bearing on the format. Since most devices support Freescale SPI format, I would suggest to use same. Also you would need to bear in mind the SPO setting based on when the data has to be captured

    Regards

    Amit

  • 0 in reply to Amit Ashara
    Intellectual 520 points

    HI Amit

    Thanks for the reply i am using ADS 1218 ADC chip . here are the timing specification

    My pol pin is always high . So looking at the timing specification should i use SSI_FRF_MOTO_MODE_3 ?

    if yes is the ans then should i follow this procedure : 

    Since i am using TM4c123GH6PGE

    1)set the FRF bit of SSICR0 to 0x0 (freescale)

    2)Set the SPO and SPH bit to 1 .

    is this the correct solution ?

  • 0 in reply to Shubham Arora
    TI__Guru**** 244400 points

    Hello Shubham,

    That is correct. You can use both clock polarities.

    Please do make sure that the SCLK frequency is as per the ADS1218 requirement

    Regards

    Amit

  • 0 in reply to Amit Ashara
    Intellectual 520 points

    Thanks Amit for reply but just to clarify that with the SCLK frequency u meant the bit rate for the SSI

    because when i use this API for multiple slave :

    SSIConfigSetExpClk(uint32_t ui32Base,uint32_t ui32SSIClk,uint32_t ui32Protocol,uint32_t ui32Mode,uint32_t ui32BitRate,
    uint32_t ui32DataWidth)

    my understanding is SSIClk is the frequency at which SSI works which is independent of slave

    but i need to set different BitRate for different slave ,

    is that correct ?

  • 0 in reply to Shubham Arora
    TI__Guru**** 244400 points

    Hello Shubham,

    The SSI Clock is the System Clock Frequency and Bit Rate is the Slave Side Clock Frequency

    Regards

    Amit