First, let me congratulate you with this project! An Open Source FPGA hardware and toolchain is really exciting. Thanks for sharing this excellent work!
In the past I have used OpalKelly boards and implemented control hardware for our lab. The OpalKelly boards come with a ip core that makes data transfer from or to the FPGA very simple. I am now looking for something similar for the tinyFPGA BX board. The simplest example would be a verilog code that allows to turn on and off the led on the board via usb and a python script on the host computer.
Currently, I have downloaded the bootloader code and trying to figure out how to modify it. Unfortunately my knowledge of the USB protocol is very limited. What confuses me is, does the boot loader really implement a serial communication? As far as I understand it, it just announces itself as one, but the communication is done via writing to an endpoint. On my osx system, the device is listed as a ‘Communication Device’ but I do not see a serial port on /dev/tty* ?