@ -4,7 +4,7 @@ In order to flash a microcontroller over USB, it needs something called a bootlo
However, it can sometimes happen that the bootloader becomes corrupted and needs reflashing, or you may want to change the bootloader to another one. It's not possible to do this with the existing bootloader, because, of course, it is already running, and cannot overwrite itself. Instead, you will need to ISP flash the microcontroller.
There are several different kinds of bootloaders available for AVR microcontrollers. Most STM32 ARM-based microcontrollers already have a USB-capable bootloader in ROM, so generally do not need to be ISP flashed.
There are several different kinds of bootloaders available for AVR microcontrollers. Most STM32 ARM-based microcontrollers already have a USB-capable bootloader in ROM, so generally do not need to be ISP flashed. The one current exception is the [STM32F103](#flashing-stm32duino-bootloader).
## Hardware
@ -260,3 +260,93 @@ For mass production purposes, it is possible to join the bootloader and QMK firm
4. Save it as a new file, for example `<keyboard>_<keymap>_production.hex`.
You can then ISP flash this combined firmware instead, which allows you to skip the extra step of flashing the QMK firmware over USB.
## Flashing STM32Duino Bootloader
As mentioned above, *most* supported STM32 devices already possess a USB DFU bootloader which cannot be overwritten, however the ROM bootloader in the STM32F103 used on the Bluepill is not USB capable. In this case an ST-Link V2 dongle is required to upload the STM32Duino bootloader to the device. These can be readily purchased for relatively cheap on eBay and other places.
This bootloader is a descendant of the Maple bootloader by Leaflabs, and is compatible with dfu-util.
### Software
To communicate with the ST-Link, you must install the following packages:
* **Linux:** will vary by distribution, but will likely be `stlink` and `openocd` through your particular package manager
Additionally, you may need to update the ST-Link's firmware with the [`STSW-LINK007`](https://www.st.com/en/development-tools/stsw-link007.html) application. Note you will be asked to provide your name and email address if you do not have an ST.com account (this does not create one).
Finally, the bootloader binary itself can be downloaded from [here](https://github.com/rogerclarkmelbourne/STM32duino-bootloader/blob/master/bootloader_only_binaries/generic_boot20_pc13.bin).
### Wiring
Connect the four-pin header on the end of the Bluepill to the matching pins on the ST-Link (the pinout will usually be printed on the side):
|ST-Link |Bluepill|
|-------------|--------|
|`GND` (6) |`GND` |
|`SWCLK` (2) |`DCLK` |
|`SWDIO` (4) |`DIO` |
|`3.3V` (8) |`3.3` |
### Flashing
Firstly, make sure both jumpers on the Bluepill are set to 0.
Check that the ST-Link can talk to the Bluepill by running `st-info --probe`:
```
Found 1 stlink programmers
version: V2J37S7
serial: 2C1219002B135937334D4E00
flash: 65536 (pagesize: 1024)
sram: 20480
chipid: 0x0410
descr: F1xx Medium-density
```
If the reported `chipid` is `0x0410`, everything is working. If it is `0x0000`, check your wiring, and try swapping the `SWDIO` and `SWCLK` pins, as some ST-Link dongles may have incorrect pinouts.
where `<path-to-bootloader>` is the path to the bootloader `.bin` file above. You can run this command from the directory you downloaded it to, so that you can simply pass in the filename.
If all goes well, you should get output similar to the following:
```
st-flash 1.7.0
2022-03-08T12:16:30 INFO common.c: F1xx Medium-density: 20 KiB SRAM, 64 KiB flash in at least 1 KiB pages.
zvecr
2 years ago