add rudimentary gpio button reading

firmware/CMakeLists.txt

     src/usb_msc.c
     src/fat_disk.c
     src/debug.c
+    src/buttons.c
+    src/controls.c
     ${CMAKE_CURRENT_BINARY_DIR}/fatfs/ff.c
     ${CMAKE_CURRENT_BINARY_DIR}/fatfs/ffunicode.c
 )

firmware/include/buttons.h

+/*
+ * buttons.h
+ */
+
+#ifndef __BUTTONS_H__
+#define __BUTTONS_H__
+
+void buttons_init(void);
+void buttons_run(void);
+
+#endif // __BUTTONS_H__
+

firmware/include/config.h

 #define INVERT_MOUSE_Y_AXIS true
 #define DEFAULT_MOUSE_SENSITIVITY PMW_CPI_TO_SENSE(500)
 
+#define DEBOUNCE_DELAY_MS 5
+
 #endif // __CONFIG_H__

firmware/include/controls.h

+/*
+ * controls.h
+ */
+
+#ifndef __CONTROLS_H__
+#define __CONTROLS_H__
+
+void controls_new(int id, bool state);
+bool controls_button_read(void);
+
+#endif // __CONTROLS_H__
+

firmware/src/buttons.c

+/*
+ * buttons.c
+ */
+
+#include "pico/stdlib.h"
+
+#include "config.h"
+#include "controls.h"
+#include "buttons.h"
+
+#define BUTTONS_COUNT 4
+uint gpio_num[BUTTONS_COUNT] = { 21, 22, 26, 27 };
+
+struct button_state {
+    uint32_t last_time;
+    bool last_state;
+};
+
+struct button_state buttons[BUTTONS_COUNT];
+
+void buttons_init(void) {
+    for (int i = 0; i < BUTTONS_COUNT; i++) {
+        gpio_init(gpio_num[i]);
+        gpio_pull_up(gpio_num[i]);
+    }
+}
+
+void buttons_run(void) {
+    for (int i = 0; i < BUTTONS_COUNT; i++) {
+        bool state = gpio_get(gpio_num[i]);
+        uint32_t now = to_ms_since_boot(get_absolute_time());
+
+        if (state != buttons[i].last_state) {
+            buttons[i].last_time = now;
+        }
+
+        if ((now - buttons[i].last_time) > DEBOUNCE_DELAY_MS) {
+            if (state != buttons[i].last_state) {
+                buttons[i].last_state = state;
+                controls_new(i, state);
+            }
+        }
+    }
+}
+

firmware/src/controls.c

+/*
+ * controls.c
+ */
+
+#include "pico/stdlib.h"
+
+#include "config.h"
+#include "controls.h"
+
+static bool button_state = false;
+
+void controls_new(int id, bool state) {
+    (void)id;
+    button_state = state;
+}
+
+bool controls_button_read(void) {
+    return button_state;
+}
+

firmware/src/main.c

 #include "usb.h"
 #include "pmw3360.h"
 #include "fat_disk.h"
+#include "buttons.h"
 
 int main(void) {
     heartbeat_init();
+    buttons_init();
 
     cnsl_init();
     usb_init();
 
     // trigger after 500ms
     // (PMW3360 initialization takes ~160ms)
-    watchdog_enable(500, 1);
+    //watchdog_enable(500, 1);
 
     debug("init done");
 
         watchdog_update();
 
         heartbeat_run();
+        buttons_run();
         usb_run();
         cnsl_run();
         pmw_run();

firmware/src/usb_hid.c

 
 #include "config.h"
 #include "pmw3360.h"
+#include "controls.h"
 #include "usb_descriptors.h"
 #include "usb_hid.h"
 
     if ( board_millis() - start_ms < interval_ms) return; // not enough time
     start_ms += interval_ms;
 
-    uint32_t const btn = board_button_read();
+    uint32_t const btn = controls_button_read();
 
     // Remote wakeup
     if ( tud_suspended() && btn ) {