How can I convert the serial signal from ADC to N-bit range signal?

Question

My project goal is to design a 'heart rate module' using zed board and ppg sensor.

I'm going to use Pmod as ADC for converting the analog signal from the ppg sensor to the digital signal so that the zedboard would be able to process it.

there is a problem at this point.

my module gets a '12-bit signal' as input,

but I found out that the Pmod provides the digital output in serial peripheral protocol.

the input of the module has 12-bit range, but the output of pmod(which will be connected the module as a module input) is only 1-bit range.

I think their bit range differs, which shouldn't

how can I solve this problem?

Answer 1

Assuming that I have understood your problem correctly, you need to design a Deserialiser module. The most common way of doing this is by creating a Shift Register.

The Shift Register operates by shifting serial data in, 1 bit at a time. When enough bits have been shifted in (determined by your application) you can shift the contents of the register out in a parallel shift. You now have parallel data.

But wait, it may not be that easy for you. You mentioned that the device you are using communicates via a SPI bus. Unless you have a SPI module that is helpfully outputting serial data (and telling your register when to shift) then you need also design some SPI compliant logic. Don't forget to pay attention to the timing requirements of the SPI port.