Add to STM code timer functionality to call Python on interrupt.

1 files changed, 90 insertions, 0 deletions

diff --git a/stm/timer.c b/stm/timer.c
new file mode 100644
index 000000000..31807d0ce
--- /dev/null
+++ b/stm/timer.c
@@ -0,0 +1,90 @@
+#include <stdint.h>
+#include <stdio.h>
+
+#include "stm_misc.h"
+#include "stm32f4xx_rcc.h"
+#include "stm32f4xx_tim.h"
+
+#include "nlr.h"
+#include "misc.h"
+#include "mpyconfig.h"
+#include "parse.h"
+#include "compile.h"
+#include "runtime.h"
+
+#include "timer.h"
+
+// TIM6 is used as an internal interrup to schedule something at a specific rate
+py_obj_t timer_py_callback;
+
+py_obj_t timer_py_set_callback(py_obj_t f) {
+    timer_py_callback = f;
+    return py_const_none;
+}
+
+py_obj_t timer_py_set_period(py_obj_t period) {
+    TIM6->ARR = py_obj_get_int(period) & 0xffff;
+    //TIM6->PSC = prescaler & 0xffff;
+    return py_const_none;
+}
+
+py_obj_t timer_py_get_value(void) {
+    return py_obj_new_int(TIM6->CNT & 0xfffff);
+}
+
+void timer_init(void) {
+    timer_py_callback = py_const_none;
+
+    // TIM6 clock enable
+    RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM6, ENABLE);
+
+    // Compute the prescaler value so TIM6 runs at 10kHz
+    uint16_t PrescalerValue = (uint16_t) ((SystemCoreClock / 2) / 10000) - 1;
+
+    // Time base configuration
+    TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure;
+    TIM_TimeBaseStructure.TIM_Period = 10000; // timer cycles at 1Hz
+    TIM_TimeBaseStructure.TIM_Prescaler = PrescalerValue;
+    TIM_TimeBaseStructure.TIM_ClockDivision = 0; // unused for TIM6
+    TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up; // unused for TIM6
+    TIM_TimeBaseInit(TIM6, &TIM_TimeBaseStructure);
+
+    // enable perhipheral preload register
+    TIM_ARRPreloadConfig(TIM6, ENABLE);
+
+    // enable interrupt when counter overflows
+    TIM_ITConfig(TIM6, TIM_IT_Update, ENABLE);
+
+    // set up interrupt
+    NVIC_InitTypeDef NVIC_InitStructure;
+    NVIC_InitStructure.NVIC_IRQChannel = TIM6_DAC_IRQn;
+    NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 0x0f; // lowest priority
+    NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0x0f; // lowest priority
+    NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
+    NVIC_Init(&NVIC_InitStructure);
+
+    // TIM6 enable counter
+    TIM_Cmd(TIM6, ENABLE);
+
+    // Python interface
+    py_obj_t m = py_module_new();
+    rt_store_attr(m, qstr_from_str_static("callback"), rt_make_function_1(timer_py_set_callback));
+    rt_store_attr(m, qstr_from_str_static("period"), rt_make_function_1(timer_py_set_period));
+    rt_store_attr(m, qstr_from_str_static("value"), rt_make_function_0(timer_py_get_value));
+    rt_store_name(qstr_from_str_static("timer"), m);
+}
+
+void timer_interrupt(void) {
+    if (timer_py_callback != py_const_none) {
+        nlr_buf_t nlr;
+        if (nlr_push(&nlr) == 0) {
+            rt_call_function_0(timer_py_callback);
+            nlr_pop();
+        } else {
+            // uncaught exception
+            printf("exception in timer interrupt\n");
+            py_obj_print((py_obj_t)nlr.ret_val);
+            printf("\n");
+        }
+    }
+}