From 10e173aaeadd589653fda89da34766322b77059d Mon Sep 17 00:00:00 2001
From: Damien George <damien.p.george@gmail.com>
Date: Sat, 1 Jun 2019 16:08:11 +1000
Subject: [PATCH] stm32/extint: Add extint_set() function for internal C access
 to EXTI.

---
 ports/stm32/extint.c | 50 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 50 insertions(+)

diff --git a/ports/stm32/extint.c b/ports/stm32/extint.c
index 59b20d5bd9..1f147d42dc 100644
--- a/ports/stm32/extint.c
+++ b/ports/stm32/extint.c
@@ -297,6 +297,53 @@ void extint_register_pin(const pin_obj_t *pin, uint32_t mode, bool hard_irq, mp_
     }
 }
 
+void extint_set(const pin_obj_t *pin, uint32_t mode) {
+    uint32_t line = pin->pin;
+
+    mp_obj_t *cb = &MP_STATE_PORT(pyb_extint_callback)[line];
+
+    extint_disable(line);
+
+    *cb = MP_OBJ_SENTINEL;
+
+    pyb_extint_mode[line] = (mode & 0x00010000) ? // GPIO_MODE_IT == 0x00010000
+        EXTI_Mode_Interrupt : EXTI_Mode_Event;
+
+    {
+        // Configure and enable the callback
+
+        pyb_extint_hard_irq[line] = 1;
+        pyb_extint_callback_arg[line] = MP_OBJ_FROM_PTR(pin);
+
+        // Route the GPIO to EXTI
+        __HAL_RCC_SYSCFG_CLK_ENABLE();
+        SYSCFG->EXTICR[line >> 2] =
+            (SYSCFG->EXTICR[line >> 2] & ~(0x0f << (4 * (line & 0x03))))
+            | ((uint32_t)(GPIO_GET_INDEX(pin->gpio)) << (4 * (line & 0x03)));
+
+        // Enable or disable the rising detector
+        if ((mode & GPIO_MODE_IT_RISING) == GPIO_MODE_IT_RISING) {
+            EXTI_RTSR |= 1 << line;
+        } else {
+            EXTI_RTSR &= ~(1 << line);
+        }
+
+        // Enable or disable the falling detector
+        if ((mode & GPIO_MODE_IT_FALLING) == GPIO_MODE_IT_FALLING) {
+            EXTI_FTSR |= 1 << line;
+        } else {
+            EXTI_FTSR &= ~(1 << line);
+        }
+
+        // Configure the NVIC
+        NVIC_SetPriority(IRQn_NONNEG(nvic_irq_channel[line]), IRQ_PRI_EXTINT);
+        HAL_NVIC_EnableIRQ(nvic_irq_channel[line]);
+
+        // Enable the interrupt
+        extint_enable(line);
+    }
+}
+
 void extint_enable(uint line) {
     if (line >= EXTI_NUM_VECTORS) {
         return;
@@ -552,6 +599,9 @@ const mp_obj_type_t extint_type = {
 
 void extint_init0(void) {
     for (int i = 0; i < PYB_EXTI_NUM_VECTORS; i++) {
+        if (MP_STATE_PORT(pyb_extint_callback)[i] == MP_OBJ_SENTINEL) {
+            continue;
+        }
         MP_STATE_PORT(pyb_extint_callback)[i] = mp_const_none;
         pyb_extint_mode[i] = EXTI_Mode_Interrupt;
    }