Share byte data from Mega 2560 to Leonardo

Projects General Guidance
1

I had a project planned to work on tonight, but I realised that I hade planned the memory (232,000 bytes of PROGMEM) of a Mega, with the USB host functionality of a Leonardo. I won't be able to do this project with any one Arduino that I have.

What is the fastest way I can reliably share the 232,000 bytes of data stored in the Mega, with the Leonardo, so that it can use them for the next part of the project. The Leonardo will send them again via USB HID 64 bytes at a time, that was the speed I was relying on when I thought the project up.

2

I would vote for serial, can go up to 2 Mbits/s. Else SPI.

Your bottleneck will be the memory in the Leonardo. If it can't get rid of the received data fast enough, you still have a problem.

3

What speed should I expect the bytes to be able to be retrieved from PROGMEM_FAR?

4

Would SD card storage on the Leonardo be fast enough?

One of the Teensy boards might be more suitable.

Much faster than you can send them over a serial connection.

< edit > Testing on code from a previous question, reading 230,400 bytes from PROGMEM_FAR, and writing to serial at 2Mbit/second, takes 1375mS. By my calculation, it should take 1152mS for the serial itself (8 bits with start and stop bit), so about 223mS off overhead.

5

Thanks for the help. I did get an SD Card module in the end.

6

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