STM32F103 Blue Pill

Runs real compiled STM32F103 "Blue Pill" firmware on an in-browser STMicroelectronics STM32F103 (ARM Cortex-M3, 72 MHz, no FPU). The default is "Blink PC13": a bare-metal C program that enables the GPIOC clock in RCC, configures PC13 as an output and blinks the on-board LED (PC13 is active-low, so the LED lights when the pin is driven low). "Timer Blink (TIM2)" blinks the same LED but times it with the TIM2 general-purpose timer instead of a busy loop — it starts TIM2 and polls the update flag (SR.UIF). "USART Hello" brings up USART1 (TX on PA9) and prints a greeting to the serial console while blinking the LED each line; "USART Counter" prints an incrementing counter over USART1. All four are original CC0 programs compiled with clang for thumbv7m. Open the debugger, or add ?debug, to single-STEP real Thumb instructions from flash at 0x08000000, set PC breakpoints and write watchpoints, and read the ARM registers (r0-r15, xPSR, N/Z/C/V) and the real STM32F103 memory map live (FLASH 0x08000000, SRAM 0x20000000, peripherals 0x40000000). A bare Blue Pill has no user input wired to the firmware and no on-board speaker, so it is honestly silent with no input pad.

Runs real compiled STM32F103 "Blue Pill" firmware on an in-browser STMicroelectronics STM32F103 (ARM Cortex-M3, 72 MHz, no FPU). The default is "Blink PC13": a bare-metal C program that enables the GPIOC clock in RCC, configures PC13 as an output and blinks the on-board LED (PC13 is active-low, so the LED lights when the pin is driven low). "Timer Blink (TIM2)" blinks the same LED but times it with the TIM2 general-purpose timer instead of a busy loop — it starts TIM2 and polls the update flag (SR.UIF). "USART Hello" brings up USART1 (TX on PA9) and prints a greeting to the serial console while blinking the LED each line; "USART Counter" prints an incrementing counter over USART1. All four are original CC0 programs compiled with clang for thumbv7m. Open the debugger, or add ?debug, to single-STEP real Thumb instructions from flash at 0x08000000, set PC breakpoints and write watchpoints, and read the ARM registers (r0-r15, xPSR, N/Z/C/V) and the real STM32F103 memory map live (FLASH 0x08000000, SRAM 0x20000000, peripherals 0x40000000). A bare Blue Pill has no user input wired to the firmware and no on-board speaker, so it is honestly silent with no input pad.

Runs real compiled STM32F103 "Blue Pill" firmware on an in-browser STMicroelectronics STM32F103 (ARM Cortex-M3, 72 MHz, no FPU). The default is "Blink PC13": a bare-metal C program that enables the GPIOC clock in RCC, configures PC13 as an output and blinks the on-board LED (PC13 is active-low, so the LED lights when the pin is driven low). "Timer Blink (TIM2)" blinks the same LED but times it with the TIM2 general-purpose timer instead of a busy loop — it starts TIM2 and polls the update flag (SR.UIF). "USART Hello" brings up USART1 (TX on PA9) and prints a greeting to the serial console while blinking the LED each line; "USART Counter" prints an incrementing counter over USART1. All four are original CC0 programs compiled with clang for thumbv7m. Open the debugger, or add ?debug, to single-STEP real Thumb instructions from flash at 0x08000000, set PC breakpoints and write watchpoints, and read the ARM registers (r0-r15, xPSR, N/Z/C/V) and the real STM32F103 memory map live (FLASH 0x08000000, SRAM 0x20000000, peripherals 0x40000000). A bare Blue Pill has no user input wired to the firmware and no on-board speaker, so it is honestly silent with no input pad.

Runs real compiled STM32F103 "Blue Pill" firmware on an in-browser STMicroelectronics STM32F103 (ARM Cortex-M3, 72 MHz, no FPU). The default is "Blink PC13": a bare-metal C program that enables the GPIOC clock in RCC, configures PC13 as an output and blinks the on-board LED (PC13 is active-low, so the LED lights when the pin is driven low). "Timer Blink (TIM2)" blinks the same LED but times it with the TIM2 general-purpose timer instead of a busy loop — it starts TIM2 and polls the update flag (SR.UIF). "USART Hello" brings up USART1 (TX on PA9) and prints a greeting to the serial console while blinking the LED each line; "USART Counter" prints an incrementing counter over USART1. All four are original CC0 programs compiled with clang for thumbv7m. Open the debugger, or add ?debug, to single-STEP real Thumb instructions from flash at 0x08000000, set PC breakpoints and write watchpoints, and read the ARM registers (r0-r15, xPSR, N/Z/C/V) and the real STM32F103 memory map live (FLASH 0x08000000, SRAM 0x20000000, peripherals 0x40000000). A bare Blue Pill has no user input wired to the firmware and no on-board speaker, so it is honestly silent with no input pad.