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ADS1274: ADS1274 connected with tms320c6745

Carlos Campos97
Prodigy 130 points
Part Number: ADS1274
Other Parts Discussed in Thread: TMS320C6745

Hi,

I´m designing a schematic and I want to connect the ADS1274 (SPI format) with the DSP tms320c6745 (I have looked the ADS1274EVM and the EVMOMAPL137 schematics) and I have some questions.

I think that the SPIx_SOMI pin (DSP) is connected with the exit of the D type flip-flop (Format 000) and the SPIx_CLK pin is connected with the SCLK input (Figure 88. ADS1274 datasheet). The CLK input is connected with and oscillator of 27MHz with a fSCLK/fCLK  ratio  of 1, 1/2, 1/4, 1/8, etc. But I don’t know where connect the DRDYn output. The DSP has a pin called SPIx_ENAn ( http://www.ti.com/lit/ds/symlink/tms320c6745.pdf pag 132)  that works as an input, when the DSP works in master mode. Could I connect the DRDYn output of the ADC to this pin or I should connect it to a GPIO pin instead?

Thank you very much. 

  • 0
    TI__Guru 66346 points
    Hello Carlos,

    I'm not familiar with this DSP. My first assumption is that the SPIx_ENAn pin is likely an active-low "chip-select" function (/CS). /CS is used by some ADCs to enable the SPI interface. The ADS1274 does not use a /CS signal, so you probably don't need to use that pin.

    The /DRDY pin on the ADS1274 is meant to be used as an interrupt by the DSP to indicate when new data is ready. You should connect this signal to a GPIO on your DSP. Even if the SPIx_ENAn pin is used as an input, I don't think connecting it to /DRDY is the right approach since /DRDY will not remain low throughout the entire duration of the data transfer. Once you detect /DRDY transition from high to low, your code should jump to an interrupt service routine to collect the data.

    Best Regards,
  • 0 in reply to Ryan Andrews
    Prodigy 130 points
    Hi Ryan,

    You're right, the /SPI_ENA has to remain low throughout the entire duration of the data transfer so I can't conncet the /DRDY pin to this one. I'll connect it to a GPIO on me DSP. Thank you very much