Arduino Due Help with SPI Set up

Official Hardware Mega Due
1

I am currently using a MikroElectronika Flip n Click board and tasked with the following:

There is an existing SPI communication going on between 2 processors on a device. I have to tap into the communication between these 2 processors with a a set of wires connected to my Flip n Click board.

My goal is simply to read the SPI data that is coming being communicated between the 2 processors. After getting this data, I have to code and convert it into instructions for a CAN SPI click board. But I have issues getting the data.

The 2 processors are only engaging in 1 way communication, as the Master is sending data to the slave and whatever the slave responds is irrelevant.

Is there a simple way to use commands in the SPI.h library to just print out the data that is being transferred? I tried setting up my board as a slave to the master, but this would bring up issues since masters can only communicate to one slave, and I do not think Arduino Due supports slave mode.
My alternative is to run the board in standard master mode, with the attached device's dataline as an SPI slave. But I don't know how to read data from a constant stream slave. All of the examples I have seen online detail how to send or transfer data to an SPI slave, but I only want to constantly read data into my board. There also is not much clear documentation about how to use the Flip n Click board and its SPI features. (which pins are MOSI, MISO, how to run it on Arduino IDE)

Any SPI sample code that works on Arduino Due/Flip n Click by having the Master read incoming data from a slave, or simpler would be very helpful.

Any help as to how I can set up a simpler way of approaching this task would be helpful.

I know that the data between the 2 processors can be read simultaneously, as a colleague demonstrated that a Beagle SPI was able to connect and display all of the MOSI data.

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2

but this would bring up issues since masters can only communicate to one slave,

As long as you don't connect the MISO signal the master will have no idea how many slaves there are and couldn't care less, you could hang 120 of them off that comms link :).

I'm not familiar with the SAM chip but you should be able to easily set it up as a slave, read the data and spew it out your CAN link.

3

Since the clock is already determined by the external master, do I need to set my arduino's clock rate? I read through the SAM datasheet and I think programmed it into slave mode by changing the registers. However I am not sure how to go about changing the clock, reading data, and storing it before printing it to Serial and testing it.

This is because most of these functions are defined in the SPI.h library (like SPI.transfer, SPI.beginTransaction) and I saw multiple posts saying that if the Arduino is in Slave mode, it won't support this SPI.h library.

4

The slave does not need to set a clock rate.

I don't know what the SPI library does as I have always written my own code. But generally you get an interrupt when there is a byte to be read.

The trouble is if the master doesn't leave a gap between bytes you may not be fast enough to read byte #N before byte #N+1 starts being shifted in. This assumes that there is no hardware buffering which is the case with AVR chips but I'm not sure about this particular ARM.

One way around this is to pole the "data available" flag, this is actually much faster than an interrupt, but of course means that the slave cannot do anything else.