Tinygo flash errors
Flashing to a port may be a source of pain with a unconfigured computer. Here are some common problems when trying to get your first program on a device.
Unable to locate any volume (Linux)
This error happens with devices such as the Pi Pico (and the Pico-W) which use the UF2 protocol for flashing programs. With this protocol, the device emulates a USB block storage device that can be mounted. When you copy a properly formatted flash image onto this virtual disk drive, the side effect is to flash that image onto the device.
For the pico with target=pico, tinygo expects to see this device in the current directory under the name RPI-RP2. If this volume is is not found,
you will get an error message like this:
failed to flash /tmp/tinygo173718394/main.uf2: unable to locate any volume: [RPI-RP2]
To fix this problem, you need to mount the volume after restarting the Pico while holding down the BOOTSEL button. You can do this manually, but it
is better to edit the /etc/fstab file to allow users to do this themselves. You can do this by adding a line like this to /etc/fstab:
LABEL=RPI-RP2 /path/to/volume/RPI-RP2 vfat defaults,umask=000,users
where you replace /path/to/volume with a pathname of your choosing. It is common for this to be put in your home directory or in a system standard
place such as /mnt/RPI-RP2, but it can also be in the directory where you expect to run tinygo. You will also need to create a directory with the path
/path/to/volume/RPI-RP2. Once you have done this and after restarting the Pico in
BOOTSEL mode, you should be able to see the Pico’s block device using this command
lsblock -f
On a typical system, the Pico will show up like this
sda
└─sda1 vfat RPI-RP2 000A-9BF3
you can mount the Pico using this command:
mount /path/to/volume/RPI-RP2
You can verify that this has worked using this command:
mount | grep RPI
If you get output that looks like this, you have succeeded in mounting the volume
/dev/sda1 on /mnt/RPI-RP2 type vfat (rw,nosuid,...lots more stuff...)
If you mounted your Pico someplace other than in your development directory, you should create a symbolic
link to the mounted volume in the directory where you plan to run tinygo. This can be done using
ln -s /mnt/RPI-RP2/
Note that editing /etc/fstab, creating the mount point directory with mkdir and creating your symbolic
link all only need to be done once. During development, you will only need to do the mount command
after restarting the Pico. After flashing the Pico, it is good practice to unmount the drive using the command
umount /path/to/volume/RPI-RP2
Permission Denied (Linux)
This error is usually encountered when flashing your first program, here’s a typical error:
avrdude: ser_open(): can't open device "/dev/ttyACM0": Permission denied
The above error may be followed by ioctl errors too.
To fix this we must make sure our user is included in the group with access to serial ports. On ubuntu and Debian this is the dialout group. The equivalent group on Arch Linux based distributions is uucp.
First we can check if we are not already part of the dialout group:
groups
The output should look something like youruser adm cdrom sudo dip plugdev lpadmin lxd sambashare. If dialout is not present in the groups we can add ourselves to it with the following command:
sudo usermod -aG dialout $(whoami)
This will add our current user to dialout group. Log out and log in again to complete the procedure. You should now be able to flash to your device.
As a last resort if this does not work you can try to modify the permissions with chmod. For the error above we may try sudo chmod a+rw /dev/ttyACM0 where /dev/ttyACM0 is the serial port we are trying to flash to.