max72xx: add support for up to 8 devices in series

max72xx/max72xx.go

@@ -4,20 +4,39 @@ package max72xx
 
 import (
 	"machine"
+
+	"tinygo.org/x/drivers"
 )
 
 type Device struct {
-	bus machine.SPI
+	bus drivers.SPI
 	cs  machine.Pin
+	n   uint8 // Number of MAX7219 devices in series
 }
 
-// NewDriver creates a new max7219 connection. The SPI wire must already be configured
+const maxNumberOfDevices = 8
+
+// NewDevice 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 {
+func NewDevice(bus drivers.SPI, cs machine.Pin) *Device {
 	return &Device{
 		bus: bus,
 		cs:  cs,
+		n:   1,
+	}
+}
+
+// NewDeviceN creates a new max7219 connection with n devices in series. The SPI wire must already be configured
+func NewDeviceN(bus drivers.SPI, cs machine.Pin, n uint8) *Device {
+	if n < 1 || n > maxNumberOfDevices {
+		n = 1
+	}
+
+	return &Device{
+		bus: bus,
+		cs:  cs,
+		n:   n,
 	}
 }
 
@@ -31,7 +50,7 @@ func (driver *Device) Configure() {
 // 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(REG_SCANLIMIT, digitNumber-1)
+	driver.writeToAll(REG_SCANLIMIT, digitNumber-1)
 }
 
 // SetIntensity sets the intensity of the diplays.
@@ -40,7 +59,7 @@ func (driver *Device) SetIntensity(intensity uint8) {
 	if intensity > 0x0F {
 		intensity = 0x0F
 	}
-	driver.WriteCommand(REG_INTENSITY, intensity)
+	driver.writeToAll(REG_INTENSITY, intensity)
 }
 
 // SetDecodeMode sets the decode mode for 7 segment displays.
@@ -51,34 +70,34 @@ func (driver *Device) SetIntensity(intensity uint8) {
 func (driver *Device) SetDecodeMode(digitNumber uint8) {
 	switch digitNumber {
 	case 1: // only decode first digit
-		driver.WriteCommand(REG_DECODE_MODE, 0x01)
+		driver.writeToAll(REG_DECODE_MODE, 0x01)
 	case 2, 3, 4: //  decode digits 3-0
-		driver.WriteCommand(REG_DECODE_MODE, 0x0F)
+		driver.writeToAll(REG_DECODE_MODE, 0x0F)
 	case 8: // decode 8 digits
-		driver.WriteCommand(REG_DECODE_MODE, 0xFF)
+		driver.writeToAll(REG_DECODE_MODE, 0xFF)
 	default:
-		driver.WriteCommand(REG_DECODE_MODE, 0x00)
+		driver.writeToAll(REG_DECODE_MODE, 0x00)
 	}
 }
 
 // StartShutdownMode sets the IC into a low power shutdown mode.
 func (driver *Device) StartShutdownMode() {
-	driver.WriteCommand(REG_SHUTDOWN, 0x00)
+	driver.writeToAll(REG_SHUTDOWN, 0x00)
 }
 
 // StartShutdownMode sets the IC into normal operation mode.
 func (driver *Device) StopShutdownMode() {
-	driver.WriteCommand(REG_SHUTDOWN, 0x01)
+	driver.writeToAll(REG_SHUTDOWN, 0x01)
 }
 
 // StartDisplayTest starts a display test.
 func (driver *Device) StartDisplayTest() {
-	driver.WriteCommand(REG_DISPLAY_TEST, 0x01)
+	driver.writeToAll(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)
+	driver.writeToAll(REG_DISPLAY_TEST, 0x00)
 }
 
 func (driver *Device) writeByte(data byte) {
@@ -92,3 +111,69 @@ func (driver *Device) WriteCommand(register, data byte) {
 	driver.writeByte(data)
 	driver.cs.High()
 }
+
+// WriteCommandN sends a command to a specific MAX7219 in the chain
+//
+// The MAX7219 uses a 16-bit serial protocol divided into two 8-bit segments:
+// - The first 8 bits (D15 to D8) represent the address of the register to write to.
+// - The second 8 bits (D7 to D0) represent the data to be written to that register.
+//
+// Register Addresses:
+// - 0x00: No-Op Register
+// - 0x01 to 0x08: Digit Registers (control individual digits/segments)
+// - 0x09: Decode Mode Register (configures decoding mode for digits)
+// - 0x0A: Intensity Register (sets brightness level)
+// - 0x0B: Scan Limit Register (sets number of digits to display)
+// - 0x0C: Shutdown Register (controls shutdown mode)
+// - 0x0F: Display Test Register (tests the display)
+//
+// Examples:
+// To set the intensity to a medium level, send the following 16-bit data:
+//
+//	WriteCommandN(0, Command{Register: REG_INTENSITY, Data: 10})
+//
+// Example: To set digit 1 on the first max72xx to display the number 5 and DP, send the following 16-bit data:
+//
+//	WriteCommandN(0, REG_DIGIT1, 5 | BcdDot})
+func (driver *Device) WriteCommandN(deviceNum uint8, register, data byte) {
+	if deviceNum >= driver.n {
+		deviceNum = 0
+	}
+
+	tmp := make([]struct {
+		Register byte
+		Data     byte
+	}, driver.n)
+	for i := range tmp {
+		tmp[i].Register = REG_NOOP
+		tmp[i].Data = 0x00
+	}
+	tmp[deviceNum].Data = data
+	tmp[deviceNum].Register = register
+
+	driver.cs.Low()
+	for _, d := range tmp {
+		driver.writeByte(d.Register)
+		driver.writeByte(d.Data)
+	}
+	driver.cs.High()
+}
+
+// writeToAll sends the same command to all devices in the chain
+func (driver *Device) writeToAll(register, data byte) {
+	tmp := make([]struct {
+		Register byte
+		Data     byte
+	}, driver.n)
+	for i := range tmp {
+		tmp[i].Register = register
+		tmp[i].Data = data
+	}
+
+	driver.cs.Low()
+	for _, d := range tmp {
+		driver.writeByte(d.Register)
+		driver.writeByte(d.Data)
+	}
+	driver.cs.High()
+}

max72xx/registers.go

@@ -16,3 +16,16 @@ const (
 	REG_SHUTDOWN     byte = 0x0C // turn on for no shutdown mode
 	REG_DISPLAY_TEST byte = 0x0F // turn off for no display test
 )
+
+// BCD (B) codes for the 7-segment display
+// B coding uses the first 4 bits to represent the character and bit 7 to represent the dot.
+// 0 - 9 represent the numbers 0 to 9
+const (
+	BcdDash  byte = 10
+	BcdE     byte = 11
+	BcdH     byte = 12
+	BcdL     byte = 13
+	BcdP     byte = 14
+	BcdBlank byte = 15
+	BcdDot   byte = 128 // 7 bit must be | with the character
+)