STM32F042 code to emulate the shutter of the Canon EOS1100D
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EOS1100D Shutter Emulation

This contains the code emulate the shutter of the Canon EOS1100D DSLR. Code is targeted to the STM32F042 processor, but any other will do as well.


All source-code is provided "AS-IS", under MIT license.

Pin mapping

Push-pull outputs: PA3 -> P1 PA4 -> P9 PA5 -> P10 PA6 -> P8 PA7 -> P12

Trigger input (w/internal pull-down): PB0 <- P5/Trigger

Peripheral use

The STM32F042 is used in "crystal-less" mode. The internal HSI48 is configured to provide SYSCLK, HCLK, PCLK at 48MHz. Peripherals are configured as follows:


Provides the timebase for internal clock. It is set to 10us ticks. It is started from 0 whenever the trigger is activated. If an overflow occurs, an error condition is presented, because the shutter sequence should always end within this period of time.


Serves as bare-bones 100us scheduler to serve monitor tasks.


PB0 is used as trigger input, EXTI is used to provide an interrupt on rising edge to signal a new shutter sequence.


Checkout this code, and install a suitable GCC toolchain for ARM.

# CC=<my toolchain>-gcc make
CC     src/main.c
CC     src/init.c
CC     src/stm32f0xx_lib/stm32f0xx_tim.c
CC     src/stm32f0xx_lib/stm32f0xx_rcc.c
CC     src/stm32f0xx_lib/stm32f0xx_misc.c
CC     src/stm32f0xx_lib/stm32f0xx_gpio.c
CC     src/stm32f0xx_lib/stm32f0xx_exti.c
CC     src/stm32f0xx_lib/stm32f0xx_syscfg.c
LD     main.elf

Next, the flash file (main.elf) can be flashed into the target. For reference, I included the Lauterbach-script I use. If you don't have a Lauterbach, then google for one of the many different procedures for tool flashers.

Note: this microcontroller uses SWD interface for flashing: PA13 <-> SWDIO PA14 <- SWCLK Pin7 <- NRST


For more project information, see: General information about the shutter signals Specific implementation details