ADS1220: multiple synchronous sampling

Hi Frank,

This can be done in a couple of different ways with the ADS1220.  The best method is to use the same clock source for all three of the ADS1220 devices.  This can be accomplished with an external oscillator operating at 4.096MHz with the output connected to the CLK input pin on the ADS1220.  By using the START/SYNC command to all three devices at the same time, all devices will start converting at essentially the same time. The conversion result only needs to be read from each device before the next conversion cycle completes, so it is not necessary to read the result from all three devices at the same time.

One potential issue with using the same SPI bus connected to all three devices is making sure that there is no output driver contention with the output of DOUT/DRDY when writing the commands to all three devices at the same time.  This would require some additional logic and control to prevent the contention issue and could be done with a buffer that has a 3-state output.  When all 3 ADS1220 have CS are low, the outputs from each ADS1220 are disabled.

Best regards,

Bob B