Add capability to force stay in DFU (and erase app) with button if

TINYUF2_DFU_BUTTON is set to 1.

This adds a check to see if a button is pressed.  If the board button is
pressed, stay if dfu mode.

If TINYUF2_DFU_BUTTON_ERASE is also set to 1, then the app is erased.

ports/mimxrt10xx/boards.c

@@ -39,6 +39,12 @@
 #include "tusb.h"
 #endif
 
+// allow board.h to change the pin configuration for the button
+#ifndef BUTTON_PIN_CONFIG
+// default to 22k pull up
+#define BUTTON_PIN_CONFIG ((1<<16) | (3<<14) | (1<<13) | (1<<12))
+#endif
+
 static bool _dfu_mode = false;
 
 // needed by fsl_flexspi_nor_boot
@@ -80,11 +86,27 @@ void board_init(void)
   GPIO_PinInit(NEOPIXEL_PORT, NEOPIXEL_PIN, &neopixel_config);
 #endif
 
+#if TINYUF2_DFU_BUTTON
+  // Button
+  IOMUXC_SetPinMux( BUTTON_PINMUX, 1U);
+  IOMUXC_SetPinConfig(BUTTON_PINMUX, BUTTON_PIN_CONFIG);
+  gpio_pin_config_t button_config = { kGPIO_DigitalInput, 0, kGPIO_NoIntmode };
+  GPIO_PinInit(BUTTON_PORT, BUTTON_PIN, &button_config);
+#endif
+
 #if TUF2_LOG
   board_uart_init(BOARD_UART_BAUDRATE);
 #endif
 }
 
+#if TINYUF2_DFU_BUTTON
+int board_button_read(void)
+{
+  // active low
+  return BUTTON_STATE_ACTIVE == GPIO_PinRead(BUTTON_PORT, BUTTON_PIN);
+}
+#endif
+
 void board_teardown(void)
 {
   // no GPIO deinit for GPIO: LED, Neopixel, Button

src/board_api.h

@@ -49,6 +49,16 @@
 #define TINYUF2_DFU_DOUBLE_TAP      0
 #endif
 
+// Force boot to DFU mode when button is pressed
+#ifndef TINYUF2_DFU_BUTTON
+#define TINYUF2_DFU_BUTTON 0
+// Should holding the DFU button perform an erase as well?
+#  ifndef TINYUF2_DFU_BUTTON_ERASE
+#    define TINYUF2_DFU_BUTTON_ERASE 0
+#  endif
+#endif
+
+
 // Use Display to draw DFU image
 #ifndef TINYUF2_DISPLAY
 #define TINYUF2_DISPLAY 0
@@ -91,6 +101,11 @@ void board_reset(void);
 // Write PWM duty value to LED
 void board_led_write(uint32_t value);
 
+#if TINYUF2_DFU_BUTTON
+  // Read button.  Return true if pressed
+  int board_button_read(void);
+#endif
+
 // Write color to rgb strip
 void board_rgb_write(uint8_t const rgb[]);
 

src/main.c

@@ -35,12 +35,15 @@
 //--------------------------------------------------------------------+
 // MACRO CONSTANT TYPEDEF PROTYPES
 //--------------------------------------------------------------------+
-//#define USE_DFU_BUTTON    1
 
 // timeout for double tap detection
 #define DBL_TAP_DELAY             500
 
+// when sensing the button state, wait this long before sampling the pin
+#define BUTTON_SETTLE_DELAY 20
+
 #ifndef DBL_TAP_REG
+
 // defined by linker script
 extern uint32_t _board_dfu_dbl_tap[];
 #define DBL_TAP_REG   _board_dfu_dbl_tap[0]
@@ -104,6 +107,24 @@ int main(void)
 static bool check_dfu_mode(void)
 {
   // TODO enable for all port instead of one with double tap
+#if TINYUF2_DFU_BUTTON
+  // always stay in dfu mode if the button is pressed.
+  // wait for a few milliseconds for the switch pin to reach its pulled value.
+  _timer_count = 0;
+  board_timer_start(1);
+  while(_timer_count < BUTTON_SETTLE_DELAY) {}
+  board_timer_stop();
+  if (board_button_read()) {
+      // force erase app if forced into bootloader mode.
+#if TINYUF2_DFU_BUTTON_ERASE
+      indicator_set(STATE_WRITING_STARTED);
+      board_flash_erase_app();
+      indicator_set(STATE_WRITING_FINISHED);
+#endif
+      return true;
+  }
+#endif
+
 #if TINYUF2_DFU_DOUBLE_TAP
   // TUF2_LOG1_HEX(&DBL_TAP_REG);