drv/button_gpio: add debounce option

This adds an option to enable debouncing gpio buttons to the gpio
button driver.

Some hubs have exhibited a need for debouncing.

Fixes: pybricks/support#716

Author: dlech

CHANGELOG.md

@@ -9,7 +9,9 @@
   is still running ([support#849]).
 - Fixed Essential hub hanging on boot when bootloader entered but USB cable
   not connected ([support#821]).
+- Fixed button needs debouncing on City/Technic/Essential hubs ([support#716]).
 
+[support#716]: https://github.com/pybricks/support/issues/716
 [support#821]: https://github.com/pybricks/support/issues/821
 [support#849]: https://github.com/pybricks/support/issues/849
 

lib/pbio/drv/button/button_gpio.c

@@ -1,36 +1,96 @@
 // SPDX-License-Identifier: MIT
-// Copyright (c) 2018-2020 The Pybricks Authors
+// Copyright (c) 2018-2022 The Pybricks Authors
 
 #include <pbdrv/config.h>
 
 #if PBDRV_CONFIG_BUTTON_GPIO
 
+#include <contiki.h>
+
 #include <pbdrv/gpio.h>
 #include <pbio/button.h>
 #include <pbio/config.h>
 #include <pbio/error.h>
 
 #include "button_gpio.h"
 
+#if PBDRV_CONFIG_BUTTON_GPIO_DEBOUNCE
+
+PROCESS(pbdrv_button_process, "button");
+
+static pbio_button_flags_t pbdrv_button_state;
+
+#endif // PBDRV_CONFIG_BUTTON_GPIO_DEBOUNCE
+
 void pbdrv_button_init(void) {
     for (int i = 0; i < PBDRV_CONFIG_BUTTON_GPIO_NUM_BUTTON; i++) {
         const pbdrv_button_gpio_platform_t *platform = &pbdrv_button_gpio_platform[i];
         pbdrv_gpio_set_pull(&platform->gpio, platform->pull);
         pbdrv_gpio_input(&platform->gpio);
     }
+
+    #if PBDRV_CONFIG_BUTTON_GPIO_DEBOUNCE
+    process_start(&pbdrv_button_process);
+    #endif
 }
 
-pbio_error_t pbdrv_button_is_pressed(pbio_button_flags_t *pressed) {
-    *pressed = 0;
+/**
+ * Reads the current button state.
+ * @returns Flags that reflect the current button state.
+ */
+static pbio_button_flags_t pbdrv_button_gpio_read(void) {
+    pbio_button_flags_t flags = 0;
 
     for (int i = 0; i < PBDRV_CONFIG_BUTTON_GPIO_NUM_BUTTON; i++) {
         const pbdrv_button_gpio_platform_t *platform = &pbdrv_button_gpio_platform[i];
+
         if (!!pbdrv_gpio_input(&platform->gpio) ^ platform->active_low) {
-            *pressed |= platform->button;
+            flags |= platform->button;
         }
     }
 
+    return flags;
+}
+
+
+pbio_error_t pbdrv_button_is_pressed(pbio_button_flags_t *pressed) {
+    #if PBDRV_CONFIG_BUTTON_GPIO_DEBOUNCE
+    *pressed = pbdrv_button_state;
+    #else
+    *pressed = pbdrv_button_gpio_read();
+    #endif
+
     return PBIO_SUCCESS;
 }
 
+#if PBDRV_CONFIG_BUTTON_GPIO_DEBOUNCE
+
+PROCESS_THREAD(pbdrv_button_process, ev, data) {
+    static struct etimer timer;
+    static pbio_button_flags_t prev, next;
+
+    PROCESS_BEGIN();
+
+    etimer_set(&timer, 10);
+
+    for (;;) {
+        PROCESS_WAIT_EVENT_UNTIL(ev == PROCESS_EVENT_TIMER && etimer_expired(&timer));
+
+        next = pbdrv_button_gpio_read();
+
+        // when we get the same state twice in a row, consider it "good"
+        if (next == prev) {
+            pbdrv_button_state = next;
+        }
+
+        prev = next;
+
+        etimer_reset(&timer);
+    }
+
+    PROCESS_END();
+}
+
+#endif // PBDRV_CONFIG_BUTTON_GPIO_DEBOUNCE
+
 #endif // PBDRV_CONFIG_BUTTON_GPIO

lib/pbio/platform/city_hub/pbdrvconfig.h

@@ -21,6 +21,7 @@
 #define PBDRV_CONFIG_BUTTON                         (1)
 #define PBDRV_CONFIG_BUTTON_GPIO                    (1)
 #define PBDRV_CONFIG_BUTTON_GPIO_NUM_BUTTON         (1)
+#define PBDRV_CONFIG_BUTTON_GPIO_DEBOUNCE           (1)
 
 #define PBDRV_CONFIG_BLOCK_DEVICE                   (1)
 #define PBDRV_CONFIG_BLOCK_DEVICE_FLASH_STM32       (1)

lib/pbio/platform/debug/pbdrvconfig.h

@@ -14,6 +14,7 @@
 #define PBDRV_CONFIG_BUTTON                         (1)
 #define PBDRV_CONFIG_BUTTON_GPIO                    (1)
 #define PBDRV_CONFIG_BUTTON_GPIO_NUM_BUTTON         (1)
+#define PBDRV_CONFIG_BUTTON_GPIO_DEBOUNCE           (1)
 
 #define PBDRV_CONFIG_CLOCK                          (1)
 #define PBDRV_CONFIG_CLOCK_STM32                    (1)

lib/pbio/platform/essential_hub/pbdrvconfig.h

@@ -45,6 +45,7 @@
 #define PBDRV_CONFIG_BUTTON                         (1)
 #define PBDRV_CONFIG_BUTTON_GPIO                    (1)
 #define PBDRV_CONFIG_BUTTON_GPIO_NUM_BUTTON         (1)
+#define PBDRV_CONFIG_BUTTON_GPIO_DEBOUNCE           (1)
 
 #define PBDRV_CONFIG_CHARGER                        (1)
 #define PBDRV_CONFIG_CHARGER_MP2639A                (1)

lib/pbio/platform/technic_hub/pbdrvconfig.h

@@ -34,6 +34,7 @@
 #define PBDRV_CONFIG_BUTTON                         (1)
 #define PBDRV_CONFIG_BUTTON_GPIO                    (1)
 #define PBDRV_CONFIG_BUTTON_GPIO_NUM_BUTTON         (1)
+#define PBDRV_CONFIG_BUTTON_GPIO_DEBOUNCE           (1)
 
 #define PBDRV_CONFIG_CLOCK                          (1)
 #define PBDRV_CONFIG_CLOCK_STM32                    (1)