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98 lines
2.8 KiB
C
98 lines
2.8 KiB
C
/*
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* My first project
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*
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* It blinks LEDs like counting in binary, when the button is pressed, it reverses the order
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*
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* Build on top of libopenocm3, blackbox parts of code (setup()) copied from
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* libopencm3-examples/examples/stm32/f1/stm32vl-discovery/button project
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*
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* Open source licence, let's say Artistic Licence, although it doesn't matter, as it is local only
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*/
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#include <libopencm3/stm32/rcc.h>
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#include <libopencm3/stm32/gpio.h>
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#include <libopencm3/stm32/f1/exti.h>
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#include <libopencm3/stm32/f1/nvic.h>
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#include <stdbool.h>
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//#define DELAY 8000000 // Should be a second, or maybe not (second iff 8MHz clk, 1/3second if 24MHz clk) // Too long!!
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#define DELAY 4000000 // This is bad -- it's a value that was found to be OK
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#define STM32F1 1 // Needed for libopencm3
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volatile enum {FORWARD, BACKWARD} direction;
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volatile bool running = false;
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void setup (void) { // All the blackbox code
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// Set up clock
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rcc_clock_setup_in_hse_8mhz_out_24mhz();
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// Enable the two GPIOs
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rcc_periph_clock_enable(RCC_GPIOC);
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rcc_periph_clock_enable(RCC_GPIOA);
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// Enable AFIO (we need that to map GPIO to EXTI)
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rcc_periph_clock_enable(RCC_AFIO);
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// Enable EXTI0 interrupt.
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// The interrupts are a bit magic, as the Internet says (the datasheet for F100RBT6B does not mention the EXTI/NVIC interface)
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// This one is for EXTI0 ~~ GPIOx0 pins
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nvic_enable_irq(NVIC_EXTI0_IRQ);
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// GPIO C8 amd C9 are the two LEDs
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gpio_set_mode(GPIOC, GPIO_MODE_OUTPUT_50_MHZ, GPIO_CNF_OUTPUT_PUSHPULL, GPIO8 | GPIO9);
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// GPIO A0 is the push button
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// And we set it as a regular button and enable its interrupts in the next block
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gpio_set_mode(GPIOA, GPIO_MODE_INPUT, GPIO_CNF_INPUT_FLOAT, GPIO0);
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// Configure the EXTI0 interrupts
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// 1. Which pin
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exti_select_source(EXTI0, GPIOA);
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// 2. Which edge
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exti_set_trigger(EXTI0, EXTI_TRIGGER_RISING);
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// 3. Enable the interrupts
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exti_enable_request(EXTI0);
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}
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// libopencm3 has a pre-declared interrupt handlers, so it needs to have this name
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void exti0_isr (void) {
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// Clear the interrupt
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exti_reset_request(EXTI0);
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// NB: For some reason it is at the begining in the examples
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// It needs to be here (possibly because of reordering, when this was at the end, I usually got the interrupt twice).
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if (!running) {
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direction = FORWARD;
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} else {
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direction = direction == FORWARD ? BACKWARD : FORWARD;
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}
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running = true;
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}
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int main (void) {
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setup();
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// Array of what leds should be on
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uint16_t states[4] = {0, GPIO9, GPIO8, GPIO9 | GPIO8};
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char state = 0;
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int i;
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// Initial wait
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while (!running) ;
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while (true) {
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for (i=0 ; i<DELAY ; i++) {
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__asm ("nop");
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}
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state = (direction == FORWARD ? (state + 1)%4 : (/*state+4-1*/ state+3)%4 ); // New state
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gpio_set(GPIOC, states[state]);
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gpio_clear(GPIOC, (GPIO8 | GPIO9) ^ states[state]);
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}
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return 0;
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}
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