Safe mode and power-on sequencing

In order to stay on the board must set HOLD(GPIO4) high early during
boot.

When running off battery the power-on button must be held for 2s to
power things on, but if it's held for too long the board powers off. We
need to disable the 1s safe mode timer in order to give the user a long
enough window to set the pins up so the button can be released and the
board stay powered on. Safe mode can be entered by holding BTN_A during
boot.

Author: bootc

ports/espressif/boards/m5stack_stick_c_plus2/board.c

@@ -96,3 +96,42 @@ static void display_init(void) {
 void board_init(void) {
     display_init();
 }
+
+bool board_requests_safe_mode(void) {
+    // Enable HOLD early on
+    config_pin_as_output_with_level(GPIO_NUM_4, true);
+
+    // Change the buttons to inputs
+    gpio_set_direction(GPIO_NUM_35, GPIO_MODE_INPUT);
+    gpio_set_pull_mode(GPIO_NUM_35, GPIO_FLOATING);
+    gpio_set_direction(GPIO_NUM_37, GPIO_MODE_INPUT);
+    gpio_set_pull_mode(GPIO_NUM_37, GPIO_FLOATING);
+    gpio_set_direction(GPIO_NUM_39, GPIO_MODE_INPUT);
+    gpio_set_pull_mode(GPIO_NUM_39, GPIO_FLOATING);
+
+    // Let the pins settle
+    mp_hal_delay_ms(1);
+
+    // Safe mode if BTN_A is held at boot (logic low)
+    return gpio_get_level(GPIO_NUM_37) == 0;  // BTN_A
+}
+
+bool espressif_board_reset_pin_number(gpio_num_t pin_number) {
+    switch (pin_number) {
+        case GPIO_NUM_4: // HOLD
+            // HOLD(G4) pin must be set high to avoid a power off when battery powered
+            config_pin_as_output_with_level(pin_number, true);
+            return true;
+
+        case GPIO_NUM_35: // BTN_C/PWR
+        case GPIO_NUM_37: // BTN_A
+        case GPIO_NUM_39: // BTN_B
+            gpio_set_direction(pin_number, GPIO_MODE_INPUT);
+            gpio_set_pull_mode(pin_number, GPIO_FLOATING);
+            return true;
+
+        default:
+            return false;
+    }
+    return false;
+}

ports/espressif/boards/m5stack_stick_c_plus2/mpconfigboard.mk

@@ -10,3 +10,8 @@ CIRCUITPY_ESP_FLASH_SIZE = 8MB
 CIRCUITPY_ESP_PSRAM_MODE = qio
 CIRCUITPY_ESP_PSRAM_FREQ = 80m
 CIRCUITPY_ESP_PSRAM_SIZE = 2MB
+
+# The safe mode wait gets us very close to the 3s time for the board to shut
+# down when BTN_C/PWR is held down. We skip the wait and instead enter safe
+# mode if BTN_A is held down during boot with no timeout.
+CIRCUITPY_SKIP_SAFE_MODE_WAIT = 1