Since the Proton C is a drop-in replacement for a Pro Micro we've made it easy to use. This page documents a handy automated process for converting keyboards, as well as documenting the manual process if you'd like to make use of Proton C features that aren't available on Pro Micros.
## Automatic Conversion
If a board currently supported in QMK uses a Pro Micro (or compatible board) and you want to use the Proton C, you can generate the firmware by appending `CONVERT_TO_PROTON_C=yes` (or `CTPC=yes`) to your make argument, like this:
make 40percentclub/mf68:default CTPC=yes
You can add the same argument to your keymap's `rules.mk`, which will accomplish the same thing.
This exposes the `CONVERT_TO_PROTON_C` flag that you can use in your code with `#ifdef`s, like this:
```c
#ifdef CONVERT_TO_PROTON_C
// Proton C code
#else
// Pro Micro code
#endif
```
If you get errors about `PORTB/DDRB`, etc not being defined, so you'll need to convert the keyboard's code to use the [GPIO Controls](internals_gpio_control.md) that will work for both ARM and AVR. This shouldn't affect the AVR builds at all.
The Proton C only has one on-board LED (C13), and by default, the TXLED (D5) is mapped to it. If you want the RXLED (B0) mapped to it instead, add this like to your `config.h`:
#define CONVERT_TO_PROTON_C_RXLED
## Feature Conversion
These are defaults based on what has been implemented for ARM boards.
| [Backlight](feature_backlight.md) | Forces [task driven PWM](feature_backlight.md#software-pwm-driver) until ARM can provide automatic configuration |
| USB Host (e.g. USB-USB converter) | Not supported (USB host code is AVR specific and is not currently supported on ARM) |
| [Split keyboards](feature_split_keyboard.md) | Partial - heavily dependent on enabled features |
## Manual Conversion
To use the Proton C natively, without having to specify `CTPC=yes`, you need to change the `MCU` line in `rules.mk`:
