machine/i2c: add interface check and implementation where missing for SetBaudRate()

src/machine/i2c.go

@@ -6,6 +6,17 @@ import (
 	"errors"
 )
 
+// If you are getting a compile error on this line please check to see you've
+// correctly implemented the methods on the I2C type. They must match
+// the i2cController interface method signatures type to type perfectly.
+// If not implementing the I2C type please remove your target from the build tags
+// at the top of this file.
+var _ interface { // 2
+	Configure(config I2CConfig) error
+	Tx(addr uint16, w, r []byte) error
+	SetBaudRate(br uint32) error
+} = (*I2C)(nil)
+
 // TWI_FREQ is the I2C bus speed. Normally either 100 kHz, or 400 kHz for high-speed bus.
 //
 // Deprecated: use 100 * machine.KHz or 400 * machine.KHz instead.

src/machine/machine_atmega.go

@@ -31,14 +31,19 @@ func (i2c *I2C) Configure(config I2CConfig) error {
 	// Activate internal pullups for twi.
 	avr.PORTC.SetBits((avr.DIDR0_ADC4D | avr.DIDR0_ADC5D))
 
+	return i2c.SetBaudRate(config.Frequency)
+}
+
+// SetBaudRate sets the communication speed for I2C.
+func (i2c *I2C) SetBaudRate(br uint32) error {
 	// Initialize twi prescaler and bit rate.
 	avr.TWSR.SetBits((avr.TWSR_TWPS0 | avr.TWSR_TWPS1))
 
 	// twi bit rate formula from atmega128 manual pg. 204:
 	// SCL Frequency = CPU Clock Frequency / (16 + (2 * TWBR))
 	// NOTE: TWBR should be 10 or higher for controller mode.
 	// It is 72 for a 16mhz board with 100kHz TWI
-	avr.TWBR.Set(uint8(((CPUFrequency() / config.Frequency) - 16) / 2))
+	avr.TWBR.Set(uint8(((CPUFrequency() / br) - 16) / 2))
 
 	// Enable twi module.
 	avr.TWCR.Set(avr.TWCR_TWEN)

src/machine/machine_atsamd21.go

@@ -732,12 +732,13 @@ func (i2c *I2C) Configure(config I2CConfig) error {
 	return nil
 }
 
-// SetBaudRate sets the communication speed for the I2C.
-func (i2c *I2C) SetBaudRate(br uint32) {
+// SetBaudRate sets the communication speed for I2C.
+func (i2c *I2C) SetBaudRate(br uint32) error {
 	// Synchronous arithmetic baudrate, via Arduino SAMD implementation:
 	// SystemCoreClock / ( 2 * baudrate) - 5 - (((SystemCoreClock / 1000000) * WIRE_RISE_TIME_NANOSECONDS) / (2 * 1000));
 	baud := CPUFrequency()/(2*br) - 5 - (((CPUFrequency() / 1000000) * riseTimeNanoseconds) / (2 * 1000))
 	i2c.Bus.BAUD.Set(baud)
+	return nil
 }
 
 // Tx does a single I2C transaction at the specified address.

src/machine/machine_atsamd51.go

@@ -1228,12 +1228,13 @@ func (i2c *I2C) Configure(config I2CConfig) error {
 	return nil
 }
 
-// SetBaudRate sets the communication speed for the I2C.
-func (i2c *I2C) SetBaudRate(br uint32) {
+// SetBaudRate sets the communication speed for I2C.
+func (i2c *I2C) SetBaudRate(br uint32) error {
 	// Synchronous arithmetic baudrate, via Adafruit SAMD51 implementation:
 	// sercom->I2CM.BAUD.bit.BAUD = SERCOM_FREQ_REF / ( 2 * baudrate) - 1 ;
 	baud := SERCOM_FREQ_REF/(2*br) - 1
 	i2c.Bus.BAUD.Set(baud)
+	return nil
 }
 
 // Tx does a single I2C transaction at the specified address.

src/machine/machine_fe310.go

@@ -229,9 +229,10 @@ type I2CConfig struct {
 	SDA       Pin
 }
 
+var i2cClockFrequency uint32 = 32000000
+
 // Configure is intended to setup the I2C interface.
 func (i2c *I2C) Configure(config I2CConfig) error {
-	var i2cClockFrequency uint32 = 32000000
 	if config.Frequency == 0 {
 		config.Frequency = 100 * KHz
 	}
@@ -241,7 +242,17 @@ func (i2c *I2C) Configure(config I2CConfig) error {
 		config.SCL = I2C0_SCL_PIN
 	}
 
-	var prescaler = i2cClockFrequency/(5*config.Frequency) - 1
+	i2c.SetBaudRate(config.Frequency)
+
+	config.SDA.Configure(PinConfig{Mode: PinI2C})
+	config.SCL.Configure(PinConfig{Mode: PinI2C})
+
+	return nil
+}
+
+// SetBaudRate sets the communication speed for I2C.
+func (i2c *I2C) SetBaudRate(br uint32) error {
+	var prescaler = i2cClockFrequency/(5*br) - 1
 
 	// disable controller before setting the prescale registers
 	i2c.Bus.CTR.ClearBits(sifive.I2C_CTR_EN)
@@ -253,9 +264,6 @@ func (i2c *I2C) Configure(config I2CConfig) error {
 	// enable controller
 	i2c.Bus.CTR.SetBits(sifive.I2C_CTR_EN)
 
-	config.SDA.Configure(PinConfig{Mode: PinI2C})
-	config.SCL.Configure(PinConfig{Mode: PinI2C})
-
 	return nil
 }
 

src/machine/machine_generic.go

@@ -107,6 +107,12 @@ func (i2c *I2C) Configure(config I2CConfig) error {
 	return nil
 }
 
+// SetBaudRate sets the I2C frequency.
+func (i2c *I2C) SetBaudRate(br uint32) error {
+	i2cSetBaudRate(i2c.Bus, br)
+	return nil
+}
+
 // Tx does a single I2C transaction at the specified address.
 func (i2c *I2C) Tx(addr uint16, w, r []byte) error {
 	i2cTransfer(i2c.Bus, &w[0], len(w), &r[0], len(r))
@@ -117,6 +123,9 @@ func (i2c *I2C) Tx(addr uint16, w, r []byte) error {
 //export __tinygo_i2c_configure
 func i2cConfigure(bus uint8, scl Pin, sda Pin)
 
+//export __tinygo_i2c_set_baud_rate
+func i2cSetBaudRate(bus uint8, br uint32)
+
 //export __tinygo_i2c_transfer
 func i2cTransfer(bus uint8, w *byte, wlen int, r *byte, rlen int) int
 

src/machine/machine_k210.go

@@ -563,7 +563,19 @@ func (i2c *I2C) Configure(config I2CConfig) error {
 		config.SCL.SetFPIOAFunction(FUNC_I2C2_SCLK)
 	}
 
-	div := CPUFrequency() / config.Frequency / 16
+	i2c.SetBaudRate(config.Frequency)
+
+	i2c.Bus.INTR_MASK.Set(0)
+	i2c.Bus.DMA_CR.Set(0x03)
+	i2c.Bus.DMA_RDLR.Set(0)
+	i2c.Bus.DMA_TDLR.Set(0x4)
+
+	return nil
+}
+
+// SetBaudRate sets the communication speed for I2C.
+func (i2c *I2C) SetBaudRate(br uint32) error {
+	div := CPUFrequency() / br / 16
 
 	// Disable controller before setting the prescale register.
 	i2c.Bus.ENABLE.Set(0)
@@ -574,11 +586,6 @@ func (i2c *I2C) Configure(config I2CConfig) error {
 	i2c.Bus.SS_SCL_HCNT.Set(uint32(div))
 	i2c.Bus.SS_SCL_LCNT.Set(uint32(div))
 
-	i2c.Bus.INTR_MASK.Set(0)
-	i2c.Bus.DMA_CR.Set(0x03)
-	i2c.Bus.DMA_RDLR.Set(0)
-	i2c.Bus.DMA_TDLR.Set(0x4)
-
 	return nil
 }
 

src/machine/machine_mimxrt1062_i2c.go

@@ -171,6 +171,12 @@ func (i2c *I2C) Configure(config I2CConfig) {
 	i2c.reset(freq)
 }
 
+// SetBaudRate sets the communication speed for I2C.
+func (i2c I2C) SetBaudRate(br uint32) error {
+	// TODO: implement
+	return nil
+}
+
 func (i2c I2C) Tx(addr uint16, w, r []byte) error {
 	// perform transmit transfer
 	if nil != w {

src/machine/machine_nrf.go

@@ -246,13 +246,8 @@ func (i2c *I2C) Configure(config I2CConfig) error {
 	i2c.setPins(config.SCL, config.SDA)
 
 	i2c.mode = config.Mode
-
 	if i2c.mode == I2CModeController {
-		if config.Frequency >= 400*KHz {
-			i2c.Bus.FREQUENCY.Set(nrf.TWI_FREQUENCY_FREQUENCY_K400)
-		} else {
-			i2c.Bus.FREQUENCY.Set(nrf.TWI_FREQUENCY_FREQUENCY_K100)
-		}
+		i2c.SetBaudRate(config.Frequency)
 
 		i2c.enableAsController()
 	} else {
@@ -262,6 +257,23 @@ func (i2c *I2C) Configure(config I2CConfig) error {
 	return nil
 }
 
+// SetBaudRate sets the I2C frequency. It has the side effect of also
+// enabling the I2C hardware if disabled beforehand.
+//
+//go:inline
+func (i2c *I2C) SetBaudRate(br uint32) error {
+	switch {
+	case br >= 400*KHz:
+		i2c.Bus.SetFREQUENCY(nrf.TWI_FREQUENCY_FREQUENCY_K400)
+	case br >= 250*KHz:
+		i2c.Bus.SetFREQUENCY(nrf.TWI_FREQUENCY_FREQUENCY_K250)
+	default:
+		i2c.Bus.SetFREQUENCY(nrf.TWI_FREQUENCY_FREQUENCY_K100)
+	}
+
+	return nil
+}
+
 // signalStop sends a stop signal to the I2C peripheral and waits for confirmation.
 func (i2c *I2C) signalStop() error {
 	tries := 0

src/machine/machine_stm32_i2c_reva.go

@@ -157,6 +157,12 @@ func (i2c *I2C) Configure(config I2CConfig) error {
 	return nil
 }
 
+// SetBaudRate sets the communication speed for I2C.
+func (i2c *I2C) SetBaudRate(br uint32) error {
+	// TODO: implement
+	return nil
+}
+
 func (i2c *I2C) Tx(addr uint16, w, r []byte) error {
 
 	if err := i2c.controllerTransmit(addr, w); nil != err {

src/machine/machine_stm32_i2c_revb.go

@@ -84,6 +84,12 @@ func (i2c *I2C) Configure(config I2CConfig) error {
 	return nil
 }
 
+// SetBaudRate sets the communication speed for I2C.
+func (i2c *I2C) SetBaudRate(br uint32) error {
+	// TODO: implement
+	return nil
+}
+
 func (i2c *I2C) Tx(addr uint16, w, r []byte) error {
 	if len(w) > 0 {
 		if err := i2c.controllerTransmit(addr, w); nil != err {