Add UF2 bootloader for USB firmware flashing

Vendored and trimmed from microsoft/uf2-samdx1, adapted to the actual
ATSAMD21G17D (128 KiB flash / 16 KiB RAM), fixing the flash/RAM-size
mismatch that the previously commented-out SAM-BA bootloader target
had (it assumed a 256 KiB SAMD21G18A). Builds as a standalone
PlatformIO environment (bootloader/platformio.ini), no python2/make
dependency. Compiles clean, fits in the 8 KiB bootloader region
(7292/8192 bytes). Not yet flashed/verified on real hardware.

bootloader/inc/configkeys.h

@@ -0,0 +1,150 @@
+#ifndef __CONFIGKEYS_H
+#define __CONFIGKEYS_H 1
+
+#define CFG_MAGIC0 0x1e9e10f1
+#define CFG_MAGIC1 0x20227a79
+
+#define CFG_PIN_ACCELEROMETER_INT 1
+#define CFG_PIN_ACCELEROMETER_SCL 2
+#define CFG_PIN_ACCELEROMETER_SDA 3
+#define CFG_PIN_BTN_A 4
+#define CFG_PIN_BTN_B 5
+#define CFG_PIN_BTN_SLIDE 6
+#define CFG_PIN_DOTSTAR_CLOCK 7
+#define CFG_PIN_DOTSTAR_DATA 8
+#define CFG_PIN_FLASH_CS 9
+#define CFG_PIN_FLASH_MISO 10
+#define CFG_PIN_FLASH_MOSI 11
+#define CFG_PIN_FLASH_SCK 12
+#define CFG_PIN_LED 13
+#define CFG_PIN_LIGHT 14
+#define CFG_PIN_MICROPHONE 15
+#define CFG_PIN_MIC_CLOCK 16
+#define CFG_PIN_MIC_DATA 17
+#define CFG_PIN_MISO 18
+#define CFG_PIN_MOSI 19
+#define CFG_PIN_NEOPIXEL 20
+#define CFG_PIN_RX 21
+#define CFG_PIN_RXLED 22
+#define CFG_PIN_SCK 23
+#define CFG_PIN_SCL 24
+#define CFG_PIN_SDA 25
+#define CFG_PIN_SPEAKER_AMP 26
+#define CFG_PIN_TEMPERATURE 27
+#define CFG_PIN_TX 28
+#define CFG_PIN_TXLED 29
+#define CFG_PIN_IR_OUT 30
+#define CFG_PIN_IR_IN 31
+#define CFG_PIN_DISPLAY_SCK 32
+#define CFG_PIN_DISPLAY_MISO 33
+#define CFG_PIN_DISPLAY_MOSI 34
+#define CFG_PIN_DISPLAY_CS 35
+#define CFG_PIN_DISPLAY_DC 36
+#define CFG_DISPLAY_WIDTH 37
+#define CFG_DISPLAY_HEIGHT 38
+#define CFG_DISPLAY_CFG0 39
+#define CFG_DISPLAY_CFG1 40
+#define CFG_DISPLAY_CFG2 41
+#define CFG_DISPLAY_CFG3 42
+#define CFG_PIN_DISPLAY_RST 43
+#define CFG_PIN_DISPLAY_BL 44
+#define CFG_PIN_SERVO_1 45
+#define CFG_PIN_SERVO_2 46
+#define CFG_PIN_BTN_LEFT 47
+#define CFG_PIN_BTN_RIGHT 48
+#define CFG_PIN_BTN_UP 49
+#define CFG_PIN_BTN_DOWN 50
+#define CFG_PIN_BTN_MENU 51
+#define CFG_PIN_LED_R 52
+#define CFG_PIN_LED_G 53
+#define CFG_PIN_LED_B 54
+#define CFG_PIN_LED1 55
+#define CFG_PIN_LED2 56
+#define CFG_PIN_LED3 57
+#define CFG_PIN_LED4 58
+#define CFG_SPEAKER_VOLUME 59
+#define CFG_PIN_JACK_TX 60
+#define CFG_PIN_JACK_SENSE 61
+#define CFG_PIN_JACK_HPEN 62
+#define CFG_PIN_JACK_BZEN 63
+#define CFG_PIN_JACK_PWREN 64
+#define CFG_PIN_JACK_SND 65
+#define CFG_PIN_JACK_BUSLED 66
+#define CFG_PIN_JACK_COMMLED 67
+#define CFG_PIN_BTNMX_LATCH 66
+#define CFG_PIN_BTNMX_CLOCK 67
+#define CFG_PIN_BTNMX_DATA 68
+#define CFG_PIN_BTN_SOFT_RESET 69
+#define CFG_ACCELEROMETER_TYPE 70
+#define CFG_DISPLAY_TYPE 78
+#define CFG_PIN_A0 100
+#define CFG_PIN_A1 101
+#define CFG_PIN_A2 102
+#define CFG_PIN_A3 103
+#define CFG_PIN_A4 104
+#define CFG_PIN_A5 105
+#define CFG_PIN_A6 106
+#define CFG_PIN_A7 107
+#define CFG_PIN_A8 108
+#define CFG_PIN_A9 109
+#define CFG_PIN_A10 110
+#define CFG_PIN_A11 111
+#define CFG_PIN_A12 112
+#define CFG_PIN_A13 113
+#define CFG_PIN_A14 114
+#define CFG_PIN_A15 115
+#define CFG_PIN_D0 150
+#define CFG_PIN_D1 151
+#define CFG_PIN_D2 152
+#define CFG_PIN_D3 153
+#define CFG_PIN_D4 154
+#define CFG_PIN_D5 155
+#define CFG_PIN_D6 156
+#define CFG_PIN_D7 157
+#define CFG_PIN_D8 158
+#define CFG_PIN_D9 159
+#define CFG_PIN_D10 160
+#define CFG_PIN_D11 161
+#define CFG_PIN_D12 162
+#define CFG_PIN_D13 163
+#define CFG_PIN_D14 164
+#define CFG_PIN_D15 165
+#define CFG_NUM_NEOPIXELS 200
+#define CFG_NUM_DOTSTARS 201
+#define CFG_DEFAULT_BUTTON_MODE 202
+#define CFG_SWD_ENABLED 203
+#define CFG_FLASH_BYTES 204
+#define CFG_RAM_BYTES 205
+#define CFG_SYSTEM_HEAP_BYTES 206
+#define CFG_LOW_MEM_SIMULATION_KB 207
+#define CFG_BOOTLOADER_BOARD_ID 208
+#define CFG_UF2_FAMILY 209
+#define CFG_PINS_PORT_SIZE 210
+
+#define ACCELEROMETER_TYPE_LIS3DH 0x32
+#define ACCELEROMETER_TYPE_MMA8453 0x38
+#define ACCELEROMETER_TYPE_FXOS8700 0x3c
+#define ACCELEROMETER_TYPE_MMA8653 0x3a
+#define ACCELEROMETER_TYPE_MSA300 0x4c
+
+#define UF2_FAMILY_ATSAMD21 0x68ed2b88
+#define UF2_FAMILY_ATSAMD51 0x55114460
+#define UF2_FAMILY_NRF52840 0x1b57745f
+#define UF2_FAMILY_STM32F103 0x5ee21072
+#define UF2_FAMILY_STM32F401 0x57755a57
+#define UF2_FAMILY_ATMEGA32 0x16573617
+#define UF2_FAMILY_CYPRESS_FX2 0x5a18069b
+
+#define PINS_PORT_SIZE_PA_16 0x10
+#define PINS_PORT_SIZE_PA_32 0x20
+#define PINS_PORT_SIZE_P0_16 0x1010
+#define PINS_PORT_SIZE_P0_32 0x1020
+
+#define DEFAULT_BUTTON_MODE_ACTIVE_HIGH_PULL_DOWN 0x11
+#define DEFAULT_BUTTON_MODE_ACTIVE_HIGH_PULL_UP 0x21
+#define DEFAULT_BUTTON_MODE_ACTIVE_HIGH_PULL_NONE 0x31
+#define DEFAULT_BUTTON_MODE_ACTIVE_LOW_PULL_DOWN 0x10
+#define DEFAULT_BUTTON_MODE_ACTIVE_LOW_PULL_UP 0x20
+#define DEFAULT_BUTTON_MODE_ACTIVE_LOW_PULL_NONE 0x30
+
+#endif // __CONFIGKEYS_H