[Chat] Instructions for loading bootloader onto bare Tomu boards

Tim Ansell mithro at mithis.com
Mon Apr 3 13:25:55 AEST 2017


Forwarded from the tomu-discuss list
<https://groups.google.com/forum/#!forum/tomu-discuss/>

Hello everyone,

It appears that I had forgotten to forward the promised instructions for
getting a bootloader onto a bare Tomu board, so here they finally are.
Better late then never!

This process is needed if you got an unflashed Tomu board at LCA2017 or
33C3, or if building your own board.

Anyone who got their Tomu boards from me *after* LCA2017 should find their
board already has the bootloader on them but these instructions are useful
if you accidently overwrite the bootloader and the board stops responding.

Instructions for flashing the bootloader onto your Tomu board using OpenOCD
and a RPi can be found at https://github.com/im-tomu/
tomu-bootloader/tree/master/openocd -- I would love instructions for
loading the bootloader using other devices but haven't had any time to
write them.

The new Tomu bootloader has the following differences to the bootloader
which ships on the EFM32HG;

 * Allow using the USB port for firmware loading without needed an external
oscillator (which doesn't exist on the Tomu board).

 * Always enter the bootloader. It does *not* require a pull up on the 'C'
pin.

 * This bootloader will identify itself as
     BOOTLOADER version EFM32HG bootloader v1.a, Chip ID 24A622015669A7A1
   The important parts are version EFM32**HG** bootloader v1.**a**

The bootloader repo is found at https://github.com/im-tomu/tomu-bootloader

Once flashed with new USB bootloader and blinky example the Tomu should
appear as a CDC-ACM serial port out of the box. Connect with a serial
program (minicom, cu, screen) and hit 'i' to get the identity info and 'b'
to start the blinky example, 'u' will allow uploading new user firmware.
*Don't* press 'd' otherwise you'll need to use JTAG to recover the device
(that is destructive upload that clears the bootloader).

A big thankyou to Aleksa Sarai (cyphar) who wrote the flashing instructions
and Jonas Jelten (TheJJ) who created the patched bootloader.

Looking forward to seeing all the cool things people do with the Tomu board!

Tim 'mithro' Ansell
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