max7219: add driver support

max72xx/max72xx.go

@@ -0,0 +1,85 @@
+// Driver works for max7219 and 7221
+// Datasheet: https://datasheets.maximintegrated.com/en/ds/MAX7219-MAX7221.pdf
+package max72xx
+
+import (
+	"machine"
+)
+
+type Device struct {
+	bus machine.SPI
+	cs  machine.Pin
+}
+
+// NewDriver creates a new max7219 connection. The SPI wire must already be configured
+// The SPI frequency must not be higher than 10MHz.
+// parameter cs: the datasheet also refers to this pin as "load" pin.
+func NewDevice(bus machine.SPI, cs machine.Pin) *Device {
+	return &Device{
+		bus: bus,
+		cs:  cs,
+	}
+}
+
+// Configure setups the pins.
+func (driver *Device) Configure() {
+	outPutConfig := machine.PinConfig{Mode: machine.PinOutput}
+
+	driver.cs.Configure(outPutConfig)
+}
+
+// SetScanLimit sets the scan limit. Maximum is 8.
+// Example: a 4 digit 7SegmentDisplay has a scan limit of 4
+func (driver *Device) SetScanLimit(digitNumber uint8) {
+	driver.WriteCommand(byte(REG_SCANLIMIT), byte(digitNumber-1))
+}
+
+// SetDecodeMode sets the decode mode for 7 segment displays.
+// digitNumber = 1 -> 1 digit gets decoded
+// digitNumber = 2 or 3, or 4 -> 4 digit are being decoded
+// digitNumber = 8 -> 8 digits are being decoded
+// digitNumber 0 || digitNumber > 8 -> no decoding is being used
+func (driver *Device) SetDecodeMode(digitNumber uint8) {
+	switch digitNumber {
+	case 1: // only decode first digit
+		driver.WriteCommand(REG_DECODE_MODE, 0x01)
+	case 2, 3, 4: //  decode digits 3-0
+		driver.WriteCommand(REG_DECODE_MODE, 0x0F)
+	case 8: // decode 8 digits
+		driver.WriteCommand(REG_DECODE_MODE, 0xFF)
+	default:
+		driver.WriteCommand(REG_DECODE_MODE, 0x00)
+	}
+}
+
+// StartShutdownMode sets the IC into a low power shutdown mode.
+func (driver *Device) StartShutdownMode() {
+	driver.WriteCommand(REG_SHUTDOWN, 0x00)
+}
+
+// StartShutdownMode sets the IC into normal operation mode.
+func (driver *Device) StopShutdownMode() {
+	driver.WriteCommand(REG_SHUTDOWN, 0x01)
+}
+
+// StartDisplayTest starts a display test.
+func (driver *Device) StartDisplayTest() {
+	driver.WriteCommand(REG_DISPLAY_TEST, 0x01)
+}
+
+// StopDisplayTest stops the display test and gets into normal operation mode.
+func (driver *Device) StopDisplayTest() {
+	driver.WriteCommand(REG_DISPLAY_TEST, 0x00)
+}
+
+func (driver *Device) writeByte(data byte) {
+	driver.bus.Transfer(data)
+}
+
+// WriteCommand write data to a given register.
+func (driver *Device) WriteCommand(register, data byte) {
+	driver.cs.Low()
+	driver.writeByte(register)
+	driver.writeByte(data)
+	driver.cs.High()
+}

max72xx/registers.go

@@ -0,0 +1,18 @@
+package max72xx
+
+const (
+	REG_NOOP         byte = 0x00
+	REG_DIGIT0       byte = 0x01
+	REG_DIGIT1       byte = 0x02
+	REG_DIGIT2       byte = 0x03
+	REG_DIGIT3       byte = 0x04
+	REG_DIGIT4       byte = 0x05
+	REG_DIGIT5       byte = 0x06
+	REG_DIGIT6       byte = 0x07
+	REG_DIGIT7       byte = 0x08
+	REG_DECODE_MODE  byte = 0x09 // turn of for led matrix, turn on for digits
+	REG_INTENSITY    byte = 0x0A
+	REG_SCANLIMIT    byte = 0x0B
+	REG_SHUTDOWN     byte = 0x0C // turn on for no shutdown mode
+	REG_DISPLAY_TEST byte = 0x0F // turn off for no display test
+)