machine: Add board support for BigTreeTech SKR Pico (#4842)

* machine: add support for BTT SKR Pico
Adds support for the BigTreeTech SKR Pico 3D-printer mainboard.
This board uses the RP2040.
* Fix build tag
* Add I2C defaults
* Run UART test instead of blinky1
* Use NoPin for I2C and SPI on BTT SKR Pico
* Cleanup comments
* Don't use ADC pin names

GNUmakefile

@@ -630,6 +630,8 @@ endif
 	@$(MD5SUM) test.hex
 	$(TINYGO) build -size short -o test.hex -target=nrf52840-mdk        examples/blinky1
 	@$(MD5SUM) test.hex
+	$(TINYGO) build -size short -o test.hex -target=btt-skr-pico        examples/uart
+	@$(MD5SUM) test.hex
 	$(TINYGO) build -size short -o test.hex -target=pca10031            examples/blinky1
 	@$(MD5SUM) test.hex
 	$(TINYGO) build -size short -o test.hex -target=reelboard           examples/blinky1

src/machine/board_btt_skr_pico.go

@@ -0,0 +1,121 @@
+//go:build btt_skr_pico
+
+// This contains the pin mappings for the BigTreeTech SKR Pico.
+//
+// Purchase link: https://biqu.equipment/products/btt-skr-pico-v1-0
+// Board schematic: https://github.com/bigtreetech/SKR-Pico/blob/master/Hardware/BTT%20SKR%20Pico%20V1.0-SCH.pdf
+// Pin diagram: https://github.com/bigtreetech/SKR-Pico/blob/master/Hardware/BTT%20SKR%20Pico%20V1.0-PIN.pdf
+
+package machine
+
+// TMC stepper driver motor direction.
+// X/Y/Z/E refers to motors for X/Y/Z and the extruder.
+const (
+	X_DIR = GPIO10
+	Y_DIR = GPIO5
+	Z_DIR = GPIO28
+	E_DIR = GPIO13
+)
+
+// TMC stepper driver motor step
+const (
+	X_STEP = GPIO11
+	Y_STEP = GPIO6
+	Z_STEP = GPIO19
+	E_STEP = GPIO14
+)
+
+// TMC stepper driver enable
+const (
+	X_ENABLE = GPIO12
+	Y_ENABLE = GPIO7
+	Z_ENABLE = GPIO2
+	E_ENABLE = GPIO15
+)
+
+// TMC stepper driver UART
+const (
+	TMC_UART_TX = UART1_TX_PIN
+	TMC_UART_RX = UART1_RX_PIN
+)
+
+// Endstops
+const (
+	X_ENDSTOP = GPIO4
+	Y_ENDSTOP = GPIO3
+	Z_ENDSTOP = GPIO25
+	E_ENDSTOP = GPIO16
+)
+
+// Fan PWM
+const (
+	FAN1_PWM = GPIO17
+	FAN2_PWM = GPIO18
+	FAN3_PWM = GPIO20
+)
+
+// Heater PWM
+const (
+	HEATER_BED_PWM      = GPIO21
+	HEATER_EXTRUDER_PWM = GPIO23
+)
+
+// Thermistors
+const (
+	THERM_BED      = GPIO26 // Bed heater
+	THERM_EXTRUDER = GPIO27 // Toolhead heater
+)
+
+// Misc
+const (
+	RGB   = GPIO24 // Neopixel
+	SERVO = GPIO29 // Servo
+	PROBE = GPIO22 // Probe
+)
+
+// Onboard crystal oscillator frequency, in MHz.
+const (
+	xoscFreq = 12 // MHz
+)
+
+// I2C. We don't have this available
+const (
+	I2C0_SDA_PIN = NoPin
+	I2C0_SCL_PIN = NoPin
+
+	I2C1_SDA_PIN = NoPin
+	I2C1_SCL_PIN = NoPin
+)
+
+// SPI. We don't have this available
+const (
+	SPI0_SCK_PIN = NoPin
+	SPI0_SDO_PIN = NoPin
+	SPI0_SDI_PIN = NoPin
+	SPI1_SCK_PIN = NoPin
+	SPI1_SDO_PIN = NoPin
+	SPI1_SDI_PIN = NoPin
+)
+
+// USB CDC identifiers
+const (
+	usb_STRING_PRODUCT      = "SKR Pico"
+	usb_STRING_MANUFACTURER = "BigTreeTech"
+)
+
+var (
+	usb_VID uint16 = 0x2e8a
+	usb_PID uint16 = 0x0003
+)
+
+// UART pins
+const (
+	UART0_TX_PIN = GPIO0
+	UART0_RX_PIN = GPIO1
+	UART1_TX_PIN = GPIO8
+	UART1_RX_PIN = GPIO9
+	UART_TX_PIN  = UART0_TX_PIN
+	UART_RX_PIN  = UART0_RX_PIN
+)
+
+var DefaultUART = UART0

targets/btt-skr-pico.json

@@ -0,0 +1,13 @@
+{
+    "inherits": [
+        "rp2040"
+    ],
+    "build-tags": ["btt_skr_pico"],
+    "serial-port": ["2e8a:000A"],
+    "ldflags": [
+        "--defsym=__flash_size=16M"
+    ],
+    "extra-files": [
+        "targets/pico-boot-stage2.S"
+    ]
+}