SteelSeries Prime — QMK Mouse Liberation

The wired SteelSeries Prime is an affordable, lightweight gaming mouse (picked up from a local discounter, B&M, for £15) built around an STM32F103C8T6 microcontroller, a TrueMove Pro optical sensor (compatible with QMK's PixArt PMW3389 driver), 6 buttons, and an RGB scroll wheel LED.

Because the fancier Prime+ shares the same MCU and optical sensor and was already ported to QMK by Dasky, adapting the standard Prime was straightforward. Converting it requires opening the shell, soldering a 5-pin SWD header, unlocking flash protection via openocd, and flashing a UF2 bootloader.

Internal PCBs

Required Tools

• Screwdrivers: PH0 (for internal PCB screws) and TX6 Torx (for external case screws beneath the skates)
• SWD Programmer: ST-Link v2 (an inexpensive clone from RobotDyn/AliExpress works fine)
• Soldering Gear: Soldering iron, 5-pin 2.54 mm pitch header strip, and 3–4 female-to-female DuPont jumper wires

Teardown & Preparation

1. Remove PTFE Skates: Carefully peel back the glued PTFE feet covering the bottom screws so they can be reused after reassembly (or keep replacement skates on hand).
2. Open the Shell: Unscrew the 4 external case screws using the TX6 driver.
3. Disconnect Ribbon Cable: Gently separate the top shell and release the internal ribbon cable using its zero-insertion-force latch lever.
4. Remove Internal PCB: Unscrew the 2 main PCB screws plus the 2 additional screws next to the scroll wheel (PH0). Lift the PCB out of the lower housing (don't worry if the small plastic alignment prong on the side of the PCB snaps).
5. Solder SWD Header: Clear any factory solder from the 5 through-holes on the SWD header footprint and solder the 2.54 mm pin header in place.

Flashing the UF2 Bootloader

1. Wire ST-Link to the Mouse PCB:
   • If powering the mouse via its USB cable, connect 3 DuPont wires: GND, SWCLK, and SWDIO.
   • If powering directly from the ST-Link, connect a 4th wire for VCC (3.3 V).

2. Download or Build the Bootloader:

   • Prebuilt Binary: firmware/uf2boot_prime.bin
   • Build from Source: Clone daskygit/uf2-prime-plus, apply the patch below to rename the USB volume/product labels for the standard Prime, and build target PRIME_PLUS:

   ```diff diff --git a/libopencm3/Makefile b/libopencm3/Makefile index d93efeac..d5c2e4d6 100644 --- a/libopencm3/Makefile +++ b/libopencm3/Makefile @@ -59,7 +59,7 @@ build: lib LIB_DIRS:=$(wildcard $(addprefix lib/,$(TARGETS))) $(LIB_DIRS): $(IRQ_DEFN_FILES:=.genhdr) @printf " BUILD $@\n"; - $(Q)$(MAKE) --directory=$@ SRCLIBDIR="$(SRCLIBDIR)" + $(Q)$(MAKE) --directory=$@ SRCLIBDIR=$(SRCLIBDIR)

   lib: $(LIB_DIRS) $(Q)true diff --git a/src/stm32f103/prime_plus/config.h b/src/stm32f103/prime_plus/config.h index d7c2b50..6fe0eb7 100644 --- a/src/stm32f103/prime_plus/config.h +++ b/src/stm32f103/prime_plus/config.h @@ -49,11 +49,11 @@ #define UF2_FAMILY 0x5ee21072

   #undef VOLUME_LABEL -#define VOLUME_LABEL "PRIMEPLUS" +#define VOLUME_LABEL "PRIME" #undef PRODUCT_NAME -#define PRODUCT_NAME "SteelSeries Prime+" +#define PRODUCT_NAME "SteelSeries Prime" #undef BOARD_ID -#define BOARD_ID "steelseries-prime-plus" +#define BOARD_ID "steelseries-prime" ```

3. Remove STM32F103 Write Protection: Using openocd (or STM32CubeProgrammer):

   sh openocd -f interface/stlink.cfg -f target/stm32f1x.cfg \ -c "init; reset halt; stm32f1x unlock 0; flash protect 0 0 last off; reset halt; exit"

4. Flash the UF2 Bootloader:

   sh openocd -f interface/stlink.cfg -f target/stm32f1x.cfg \ -c "program uf2boot.bin verify reset exit 0x8000000"

5. Reassemble: Disconnect power and remove the ST-Link jumper wires, then reassemble the PCB, ribbon cable, shell, and skates.

QMK Firmware

1. Enter UF2 Bootloader Mode: Hold down the underside CPI button while plugging in the USB cable. A removable USB mass-storage drive (PRIME) will mount on your computer.

2. Flash QMK:

   • Prebuilt UF2: Download firmware/steelseries_prime_default.uf2 and copy it onto the mounted drive.
   • Compile from Source:

   bash git clone --recurse-submodules -b mlego_dev https://github.com/alinelena/qmk_firmware.git qmk-alin cd qmk-alin qmk compile -kb steelseries/prime -km default qmk flash -kb steelseries/prime -km default