AD7656-1 standalone serial connection with arduino mega

Hello There,

I am little confused in using AD7656-1 with Arduino Mega.
I have made the following pinout connection for ADC with MEGA as described in the datasheet for Serial Communication, but still, the output array is not changing the values upon the change in analog values.

My pin configuration is as follows
const int CS = 30;
const int CS1 = 53; //dummy pin for SPI
const int CONVST = 14;
const int RESET = 15;
const int NOTSTBY = 31;

I am using code which is mentioned in GIT here

Can anyone please identify the mistake since my output is a constant number with a value of 32767

  • Hi,

    It looks like you are operating the AD7656 in hardware control mode. Have you confirmed that the external reference you have supplied is correct at the pin (Pin 51). Are all other supplies appearing as expected?

    Could you share a scope plot of the BUSY, CONVST and relevant data lines when you attempt to read back data from the part?



  • Thanks Niall for your response, 

    Actually, there were several issues, and now its working.

    1) There was no AVcc supply connected to decoupling capacitors on all AVcc pins

    2) An external reference of 2.5V is used and was not connected with Reference buffer decoupling capacitors

    I am not using the BUSY pin to detect the conversion since my conversion is in continuous mode.

    It's Working now