microbit: add functions for LED matrix and correct button pin mapping

Signed-off-by: Ron Evans <ron@hybridgroup.com>

src/machine/board_microbit.go

@@ -1,15 +1,20 @@
-// +build nrf,microbit
+// +build nrf51,microbit
 
 package machine
 
+import (
+	"device/nrf"
+	"errors"
+)
+
 // The micro:bit does not have a 32kHz crystal on board.
 const HasLowFrequencyCrystal = false
 
 // Buttons on the micro:bit (A and B)
 const (
-	BUTTON  = BUTTON1
+	BUTTON  = BUTTONA
-	BUTTON1 = 5
+	BUTTONA = 17
-	BUTTON2 = 11
+	BUTTONB = 26
 )
 
 // UART pins
@@ -30,3 +35,64 @@ const (
 	SDA_PIN = 20
 	SCL_PIN = 19
 )
+
+// LED matrix pins
+const (
+	LED_COL_1 = 4
+	LED_COL_2 = 5
+	LED_COL_3 = 6
+	LED_COL_4 = 7
+	LED_COL_5 = 8
+	LED_COL_6 = 9
+	LED_COL_7 = 10
+	LED_COL_8 = 11
+	LED_COL_9 = 12
+	LED_ROW_1 = 13
+	LED_ROW_2 = 14
+	LED_ROW_3 = 15
+)
+
+// matrixSettings has the legs of the LED grid in the form {row, column} for each LED position.
+var matrixSettings = [5][5][2]uint8{
+	{{LED_ROW_1, LED_COL_1}, {LED_ROW_2, LED_COL_4}, {LED_ROW_1, LED_COL_2}, {LED_ROW_2, LED_COL_5}, {LED_ROW_1, LED_COL_3}},
+	{{LED_ROW_3, LED_COL_4}, {LED_ROW_3, LED_COL_5}, {LED_ROW_3, LED_COL_6}, {LED_ROW_3, LED_COL_7}, {LED_ROW_3, LED_COL_8}},
+	{{LED_ROW_2, LED_COL_2}, {LED_ROW_1, LED_COL_9}, {LED_ROW_2, LED_COL_3}, {LED_ROW_3, LED_COL_9}, {LED_ROW_2, LED_COL_1}},
+	{{LED_ROW_1, LED_COL_8}, {LED_ROW_1, LED_COL_7}, {LED_ROW_1, LED_COL_6}, {LED_ROW_1, LED_COL_5}, {LED_ROW_1, LED_COL_4}},
+	{{LED_ROW_3, LED_COL_3}, {LED_ROW_2, LED_COL_7}, {LED_ROW_3, LED_COL_1}, {LED_ROW_2, LED_COL_6}, {LED_ROW_3, LED_COL_2}}}
+
+// InitLEDMatrix initializes the LED matrix, by setting all of the row/col pins to output
+// then calling ClearLEDMatrix.
+func InitLEDMatrix() {
+	set := 0
+	for i := LED_COL_1; i <= LED_ROW_3; i++ {
+		set |= 1 << uint8(i)
+	}
+	nrf.GPIO.DIRSET = nrf.RegValue(set)
+	ClearLEDMatrix()
+}
+
+// ClearLEDMatrix clears the entire LED matrix.
+func ClearLEDMatrix() {
+	set := 0
+	for i := LED_COL_1; i <= LED_COL_9; i++ {
+		set |= 1 << uint8(i)
+	}
+	nrf.GPIO.OUTSET = nrf.RegValue(set)
+	nrf.GPIO.OUTCLR = (1 << LED_ROW_1) | (1 << LED_ROW_2) | (1 << LED_ROW_3)
+}
+
+// SetLEDMatrix turns on a single LED on the LED matrix.
+// Currently limited to a single LED at a time, it will clear the matrix before setting it.
+func SetLEDMatrix(x, y uint8) error {
+	if x > 4 || y > 4 {
+		return errors.New("Invalid LED matrix row or column")
+	}
+
+	// Clear matrix
+	ClearLEDMatrix()
+
+	nrf.GPIO.OUTSET = (1 << matrixSettings[y][x][0])
+	nrf.GPIO.OUTCLR = (1 << matrixSettings[y][x][1])
+
+	return nil
+}