Arduino Nano 33 BLE Tock Bootloader

This is the implementation of the Tock bootloader for the Arduino Nano 33 BLE board. The bootloader runs using the CDC-ACM over USB stack.

Compiling

We actually need to compile the bootloader twice, at two different addresses. The main bootloader will reside at address 0x00000000 in flash. That is the default address specified in the layout.ld linker script. However, we also need a temporary "helper" bootloader compiled for address 0x10000. We will use the helper bootloader to replace the stock Nano 33 BLE bootloader with our own.

Here are the steps:

make
cp ../../target/thumbv7em-none-eabi/release/nano33ble-bootloader.bin ./nano33ble-bootloader-0x00000.bin


# Edit layout.ld.
# Change "rom (rx)  : ORIGIN = 0x00000000, LENGTH = 64K" to
#        "rom (rx)  : ORIGIN = 0x00010000, LENGTH = 64K"

# Edit build.rs
# Change "bootloader_attributes::write_flags(&mut f, "1.1.0", 0x10000);" to
#        "bootloader_attributes::write_flags(&mut f, "1.1.0", 0x20000);"

make
cp ../../target/thumbv7em-none-eabi/release/nano33ble-bootloader.bin ./nano33ble-bootloader-0x10000.bin

# Undo changes
git stash