Hello STM32

# Makefile for building basic STM32 projects
#
# Michael Hope <michaelh@juju.net.nz>, 2010
#

# Using the CodeSourcery 2009q3 Lite ARM EABI tools
CROSS_COMPILE = arm-none-eabi-
CC = $(CROSS_COMPILE)gcc
OBJCOPY = $(CROSS_COMPILE)objcopy

# Name of the startup file.  'hd' for high density
STARTUP = startup_stm32f10x_hd.s

CFLAGS = -mcpu=cortex-m3 -mthumb -O -g

# List of all binaries to build
all: hello.bin

# Create a raw binary file from the ELF version
hello.bin: hello.elf
        $(OBJCOPY) -O binary $< $@

# Create the ELF version by mixing together the startup file,
# application, and linker file
hello.elf: $(STARTUP) hello.c
        $(CC) -o $@ $(CFLAGS) -nostartfiles -Wl,-Tstm32.ld $^

# Program the binary to the board using the builtin serial bootloader
program:
        stm32loader.py -p /dev/ttyUSB0 -ewv hello.bin

# Remove the temporary files
clean:
        rm -f *.o *.elf *.bin

/// A very basic STM32 demo that runs of the internal oscillator,
/// flashes a LED, and writes out some serial data.
///
/// Michael Hope <michaelh@juju.net.nz>, 2010
///
#include "stm32f10x.h"

/// Spin delay
void delay(int count)
{
    // volatile so that the compiler doesn't optimise it out
    volatile int i;

    for (i = 0; i < 100000; i++)
    {
    }
}

/// Main function.  Called by the startup code.
int main(void)
{
    // Most of the peripherals are connected to APB2.  Turn on the
    // clocks for the interesting peripherals
    RCC->APB2ENR = 0
        // Turn on USART1
        | RCC_APB2ENR_USART1EN
        // Turn on IO Port A
        | RCC_APB2ENR_IOPAEN
        // Turn on IO Port B
        | RCC_APB2ENR_IOPBEN
        // Turn on the alternate function block
        | RCC_APB2ENR_AFIOEN;

    // Put Port A pins 8 through 15 into alternate function/50 MHz
    // mode.
    GPIOA->CRH = 0xBBBBBBBB;

    // Put PB0 into push pull 50 MHz mode
    GPIOB->CRL = 0x03;

    // The internal RC oscillator runs at 8 MHz.  The divide by 16
    // combined with the fractional divider means we just divide the
    // bus clock by the baud rate
    USART1->BRR = 8000000/38400;
    // Enable the UART, TX, and RX circuit
    USART1->CR1 = USART_CR1_UE | USART_CR1_TE | USART_CR1_RE;

    // Nothing else /needs/ to be setup but you could go further.  The
    // chip defaults to 8 MHz RC with the busses running at the same
    // speed as the core.

    for (;;)
    {
        // Around 1/4 of a second
        delay(100000);

        // Write out a character
        USART1->DR = 'H';
        // Turn all pins on
        GPIOB->ODR = ~0;

        delay(100000);

        // Write out another.  Note that the delay takes long enough
        // so we know that TX is empty
        USART1->DR = 'i';
        // Turn all pins off
        GPIOB->ODR = 0;
    }
}