tinyprog WSL - using TinyFPGA BX in Windows Subsystem for Linux - Part 1

Recently, I encountered a problem getting the tinyFPGA BX to be recognized in WSL. I submitted a WSL issue on GitHub that was acknowledged and promptly closed as a duplicate, as apparently no USB devices are currently supported in WSL. I am almost certain that I previously had this working. A quick Google search, and others appear to be using WSL as well.

TL;DR - I created a gist for the entire WSL toolchain setup for the TinyFPGA.

The problem that I encountered: is that although a Windows DOS prompt sees the device:

C:\Users\gojimmypi>tinyprog

    TinyProg CLI
    ------------
    Using device id 1d50:6130
    Only one board with active bootloader, using it.

WSL does not:

gojimmypi@MYHOST: ~
0 $ tinyprog

    TinyProg CLI
    ------------
    Using device id 1d50:6130
    No port was specified and no active bootloaders found.
    Activate bootloader by pressing the reset button.

Given the comments in my GitHub issue about libusb having never been supported in WSL, I wondered how it could have previously worked? Curiously, I discovered that the tinyFPGA can use either the serial port or the USB drivers (note the last two options: no libusb support in WSL, but COM ports via pyserial should work):

usage: tinyprog [-h] [-l] [-p PROGRAM] [-u PROGRAM_USERDATA]
                [--program-image PROGRAM_IMAGE] [-b] [-c COM] [-i ID]
                [-d DEVICE] [-a ADDR] [-m] [--update-bootloader] [--libusb]
                [--pyserial]

optional arguments:
  -h, --help            show this help message and exit
  -l, --list            list connected and active FPGA boards
  -p PROGRAM, --program PROGRAM
                        program FPGA board with the given user bitstream
  -u PROGRAM_USERDATA, --program-userdata PROGRAM_USERDATA
                        program FPGA board with the given user data
  --program-image PROGRAM_IMAGE
                        program FPGA board with a combined user bitstream and
                        data
  -b, --boot            command the FPGA board to exit the bootloader and load
                        the user configuration
  -c COM, --com COM     serial port name
  -i ID, --id ID        FPGA board ID
  -d DEVICE, --device DEVICE
                        device id (vendor:product); default is (1d50:6130)
  -a ADDR, --addr ADDR  force the address to write the bitstream to
  -m, --meta            dump out the metadata for all connected boards in JSON
  --update-bootloader   check for new bootloader and update eligible connected
                        boards
  --libusb              try using libusb to connect to boards without a serial
                        driver attached
  --pyserial            use pyserial to connect to boards

So in theory, this should have forced the issue in WSL and used the serial port, but no luck:

tinyprog --pyserial --list

    TinyProg CLI
    ------------
    Using device id 1d50:6130
    No port was specified and no active bootloaders found.
    Activate bootloader by pressing the reset button.

I also tried setting permissions, just in case:

sudo usermod -a -G dialout $USER
sudo usermod -a -G tty $USER

Microsoft claims that Serial COM ports have been supported on WSL since Windows Insider Build 16176. There's also this WSL issue #1929 that indicates serial port issues have been resolved.

Annoyingly, although Linux starts counting at zero, Microsoft instead apparently decided to instead start at 1 for serial ports in WSL.  Thus /dev/ttyS0 for Linux is COM1: on the PC, however COM1: will be /dev/ttyS1 on WSL.

Google Search Result for "linux list serial ports"

I also opened a new Recognizing TinyFPGA BX in WSL topic on the tinyFPGA discourse site.

UPDATE: many thanks to lawrie.griffiths for his help on the tinyFPGA discourse thread for determining that although the --list and --meta parameters do not currently work in WSL, forcing a reboot with -b and most importantly, programming with -p while explicitly naming the com port with the -c option does work! Woohoo :)

Here are the commands in WSL of interest:

# force tinyFPGA to exit bootloader (reset or unplug board afterwards as needed)
tinyprog -b -c /dev/ttyS12

# program the tinyFPGA, while explicitly naming the port
tinyprog  --com /dev/ttyS12 -p hello_word.bin

As a reminder, do not modify WSL filesystem file from Windows! Yes, I've seen some pretty weird things happen when I tested that. But feel free to edit any other files. For instance, the entire C:\ directory is available in WSL as /mnt/c/.


Check out my next blog on setting up a soft RISC-V CPU on the tinyFPGA.

Resources, Inspiration, Credits, and Other Links:

• TinyFPGA BX User Guide
• https://github.com/tinyfpga/TinyFPGA-BX
• Serial Support on the Windows Subsystem for Linux
• How To Check and Use Serial Ports Under Linux
• github.com/Microsoft/WSL/issues/ - COM Port Access in WSL #1929
• superuser.com - How do I know which /dev/ttyS* is my serial port?

Please leave comments, ideas, suggestions below (moderated, sometimes delayed) or send me a message at gmail, or find me on twitter.