machine/samd51: add DAC support (#1198)

* machine/samd51: add DAC support

Makefile

@@ -303,6 +303,8 @@ smoketest:
 	@$(MD5SUM) test.hex
 	$(TINYGO) build -size short -o test.hex -target=circuitplay-express examples/dac
 	@$(MD5SUM) test.hex
+	$(TINYGO) build -size short -o test.hex -target=pyportal            examples/dac
+	@$(MD5SUM) test.hex
 ifneq ($(AVR), 0)
 	$(TINYGO) build -size short -o test.hex -target=atmega1284p         examples/serial
 	@$(MD5SUM) test.hex

src/examples/dac/circuitplay_express.go

@@ -0,0 +1,13 @@
+// +build circuitplay_express
+
+package main
+
+import (
+	"machine"
+)
+
+func init() {
+	enable := machine.PA30
+	enable.Configure(machine.PinConfig{Mode: machine.PinOutput})
+	enable.Set(true)
+}

src/examples/dac/dac.go

@@ -10,16 +10,12 @@ import (
 )
 
 func main() {
-	enable := machine.PA30
-	enable.Configure(machine.PinConfig{Mode: machine.PinOutput})
-	enable.Set(true)
-
 	speaker := machine.A0
 	speaker.Configure(machine.PinConfig{Mode: machine.PinOutput})
 
 	machine.DAC0.Configure(machine.DACConfig{})
 
-	data := []uint16{32768, 8192, 2048, 512, 0}
+	data := []uint16{0xFFFF, 0x8000, 0x4000, 0x2000, 0x1000, 0x0000}
 
 	for {
 		for _, val := range data {

src/examples/dac/pyportal.go

@@ -0,0 +1,13 @@
+// +build pyportal
+
+package main
+
+import (
+	"machine"
+)
+
+func init() {
+	enable := machine.SPK_SD
+	enable.Configure(machine.PinConfig{Mode: machine.PinOutput})
+	enable.Set(true)
+}

src/machine/board_wioterminal.go

@@ -132,9 +132,6 @@ const (
 	PIN_DAC0 = PA02
 	PIN_DAC1 = PA05
 
-	DAC0 = PIN_DAC0
-	DAC1 = PIN_DAC1
-
 	// FPO Analog RPIs
 	//FPC_A7  = FPC_D7
 	//FPC_A8  = FPC_D8

src/machine/machine_atsamd51.go

@@ -2297,3 +2297,61 @@ func ResetProcessor() {
 
 	arm.SystemReset()
 }
+
+// DAC on the SAMD51.
+type DAC struct {
+}
+
+var (
+	DAC0 = DAC{}
+)
+
+// DACConfig placeholder for future expansion.
+type DACConfig struct {
+}
+
+// Configure the DAC.
+// output pin must already be configured.
+func (dac DAC) Configure(config DACConfig) {
+	// Turn on clock for DAC
+	sam.MCLK.APBDMASK.SetBits(sam.MCLK_APBDMASK_DAC_)
+
+	// Use Generic Clock Generator 4 as source for DAC.
+	sam.GCLK.PCHCTRL[42].Set((sam.GCLK_PCHCTRL_GEN_GCLK4 << sam.GCLK_PCHCTRL_GEN_Pos) | sam.GCLK_PCHCTRL_CHEN)
+	for sam.GCLK.SYNCBUSY.HasBits(sam.GCLK_SYNCBUSY_GENCTRL_GCLK4 << sam.GCLK_SYNCBUSY_GENCTRL_Pos) {
+	}
+
+	// reset DAC
+	sam.DAC.CTRLA.Set(sam.DAC_CTRLA_SWRST)
+
+	// wait for reset complete
+	for sam.DAC.CTRLA.HasBits(sam.DAC_CTRLA_SWRST) {
+	}
+	for sam.DAC.SYNCBUSY.HasBits(sam.DAC_SYNCBUSY_SWRST) {
+	}
+
+	// enable
+	sam.DAC.CTRLB.Set(sam.DAC_CTRLB_REFSEL_VREFPU << sam.DAC_CTRLB_REFSEL_Pos)
+	sam.DAC.DACCTRL[0].SetBits((sam.DAC_DACCTRL_CCTRL_CC12M << sam.DAC_DACCTRL_CCTRL_Pos) | sam.DAC_DACCTRL_ENABLE)
+	sam.DAC.CTRLA.Set(sam.DAC_CTRLA_ENABLE)
+
+	for sam.DAC.SYNCBUSY.HasBits(sam.DAC_SYNCBUSY_ENABLE) {
+	}
+	for !sam.DAC.STATUS.HasBits(sam.DAC_STATUS_READY0) {
+	}
+}
+
+// Set writes a single 16-bit value to the DAC.
+// Since the ATSAMD51 only has a 12-bit DAC, the passed-in value will be scaled down.
+func (dac DAC) Set(value uint16) error {
+	sam.DAC.DATA[0].Set(value >> 4)
+	syncDAC()
+	return nil
+}
+
+func syncDAC() {
+	for !sam.DAC.STATUS.HasBits(sam.DAC_STATUS_EOC0) {
+	}
+	for sam.DAC.SYNCBUSY.HasBits(sam.DAC_SYNCBUSY_DATA0) {
+	}
+}