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ADS1234 chip select for SPI

Samuel Raj1
Intellectual 280 points

Other Parts Discussed in Thread: MSP430G2553, ADS1234

Hello....

I am trying out the ADS1234 for my load cell application, was wondering if I can use the /PDWM pin to act as a chip select are there any disadvantages to it? I am using 2 x ADS1234 to read a total of 8 loadcells respectively. I have tied the A0 and A1 pins together and using the MSP430G2553. VDD is 3.3V and AVDD is 5V.

Samuel

  • 0
    TI__Guru** 113765 points

    Hi Samuel,

    Just to make sure I'm clear on what you are doing, A0 and A1 are not tied together right?  Did you mean that on both ADS1234 the A0 pins were tied together (and the A1 on both devices tied together)?

    I have never tried using the PDWN pin as a chip select, so I don't know if the pins are driven or if they tri-state. Another problem is the startup delay time when you access a device and take a measurement. 

    You could try another approach, and it works well if you are using the same clock oscillator for both devices.  Instead of using the SPI peripheral, bit-bang the communication instead.  You actually use the same number of pins from the micro and can essentially read from both devices at the same time.  One GPIO is used as an output for SCLK, the other two pins are inputs.  One is connected to the DOUT of one of the ADS1234s and the second input to the DOUT of the other ADS1234.  If the clocks are the same for both ADS1234 they will be synchronized at the data available at the same time.

    Best regards,

    Bob B