STM32F2: Add timer_get_af().

Pull some code out of the F2 pinMode() into a utility function. This
feels generally useful enough to be exposed to the users (it will, for
example, make it easier to implement input capture in a clean way).

Signed-off-by: Marti Bolivar <mbolivar@leaflabs.com>

3 files changed, 53 insertions, 31 deletions

diff --git a/libmaple/stm32f2/include/series/timer.h b/libmaple/stm32f2/include/series/timer.h
index 0d959d0..ed473b4 100644
--- a/libmaple/stm32f2/include/series/timer.h
+++ b/libmaple/stm32f2/include/series/timer.h
@@ -34,6 +34,7 @@
 #define _LIBMAPLE_STM32F2_TIMER_H_
 
 #include <libmaple/libmaple_types.h>
+#include <libmaple/gpio.h>      /* for gpio_af */
 
 /*
  * Register maps and base pointers
@@ -167,4 +168,10 @@ extern struct timer_dev *TIMER12;
 extern struct timer_dev *TIMER13;
 extern struct timer_dev *TIMER14;
 
+/*
+ * Routines
+ */
+
+gpio_af timer_get_af(struct timer_dev *dev);
+
 #endif
diff --git a/libmaple/stm32f2/timer.c b/libmaple/stm32f2/timer.c
index 3f9a8d2..f644b16 100644
--- a/libmaple/stm32f2/timer.c
+++ b/libmaple/stm32f2/timer.c
@@ -114,6 +114,51 @@ void timer_foreach(void (*fn)(timer_dev*)) {
     fn(TIMER14);
 }
 
+/**
+ * @brief Get the GPIO alternate function corresponding to a timer.
+ *
+ * For example, if dev is TIMER1, this function returns
+ * GPIO_AF_TIM_1_2. This is useful for e.g. using gpio_set_af() to set
+ * a pin's alternate function to a timer.
+ *
+ * Note that the timer gpio_afs are shared with other timers (and
+ * sometimes with CAN). For example, timers 1 and 2 both use
+ * GPIO_AF_TIM_1_2. Because of that, it can pay to e.g not point two
+ * timers at the same pin.
+ *
+ * @param dev Timer device, must not be TIMER6 or TIMER7.
+ * @return gpio_af corresponding to dev
+ * @see gpio_set_af
+ * @see gpio_af
+ */
+gpio_af timer_get_af(timer_dev *dev) {
+    rcc_clk_id clk_id = dev->clk_id;
+    /* Timers 6 and 7 don't have any capture/compare, so they can't do
+     * PWM (and in fact have no AF values). */
+    ASSERT(clk_id != RCC_TIMER6 && clk_id != RCC_TIMER7);
+    switch(dev->clk_id) {
+    case RCC_TIMER1:        // fall-through
+    case RCC_TIMER2:
+        return GPIO_AF_TIM_1_2;
+    case RCC_TIMER3:        // fall-through
+    case RCC_TIMER4:        // ...
+    case RCC_TIMER5:
+        return GPIO_AF_TIM_3_4_5;
+    case RCC_TIMER8:        // fall-through
+    case RCC_TIMER9:        // ...
+    case RCC_TIMER10:       // ...
+    case RCC_TIMER11:
+        return GPIO_AF_TIM_8_9_10_11;
+    case RCC_TIMER12:       // fall-through
+    case RCC_TIMER13:       // ...
+    case RCC_TIMER14:
+        return GPIO_AF_CAN_1_2_TIM_12_13_14;
+    default:
+        ASSERT(0);          // Can't happen
+        return (gpio_af)-1;
+    }
+}
+
 /*
  * IRQ handlers
  *
diff --git a/wirish/stm32f2/wirish_digital.cpp b/wirish/stm32f2/wirish_digital.cpp
index bf9dcf5..4d46f1c 100644
--- a/wirish/stm32f2/wirish_digital.cpp
+++ b/wirish/stm32f2/wirish_digital.cpp
@@ -91,37 +91,7 @@ void pinMode(uint8 pin, WiringPinMode w_mode) {
         if (info->timer_device == NULL) {
             return;
         }
-        gpio_af timer_af;
-        /* TODO make this code a <libmaple/timer.h> convenience
-         * routine for series that support GPIO alternate
-         * functions. */
-        switch(info->timer_device->clk_id) {
-        case RCC_TIMER1:        // fall-through
-        case RCC_TIMER2:
-            timer_af = GPIO_AF_TIM_1_2;
-            break;
-        case RCC_TIMER3:        // fall-through
-        case RCC_TIMER4:        // ...
-        case RCC_TIMER5:
-            timer_af = GPIO_AF_TIM_3_4_5;
-            break;
-        /* Timers 6 and 7 don't have any capture/compare, so they
-         * can't do PWM (and in fact have no AF values). */
-        case RCC_TIMER8:        // fall-through
-        case RCC_TIMER9:        // ...
-        case RCC_TIMER10:       // ...
-        case RCC_TIMER11:
-            timer_af = GPIO_AF_TIM_8_9_10_11;
-            break;
-        case RCC_TIMER12:       // fall-through
-        case RCC_TIMER13:       // ...
-        case RCC_TIMER14:
-            timer_af = GPIO_AF_CAN_1_2_TIM_12_13_14;
-            break;
-        default:
-            ASSERT(0);          // Can't happen
-            return;
-        }
+        gpio_af timer_af = timer_get_af(info->timer_device);
         timer_set_mode(info->timer_device, info->timer_channel, TIMER_PWM);
         gpio_set_af(info->gpio_device, info->gpio_bit, timer_af);
     }