First button press, programs 144K to the cart (reading from SD), second press reads 144K from the cart (writes to SD) and the last press verifies by reading from both SD and cart at the same time. Last part, where I have to get back to the computer, to hit return on a command line tool, that programs the cart remotely.
Timing: 9.19sec., 2.29sec., 2.1sec. and 21.25sec. via USB serial.
Probably gonna add full MCP I/O support to it as well.
https://www.youtube.com/watch?v=RZx2IFwyRb8