From e0a5b2ee2a4d5b19b531d2ca02f67cb33d9bf78f Mon Sep 17 00:00:00 2001
From: deadprogram <ron@hybridgroup.com>
Date: Sun, 22 Jan 2023 22:59:24 +0100
Subject: [PATCH 1/8] machine/i2c: add interface check and placeholder
 implementation where missing for SetBaudRate()

Signed-off-by: deadprogram <ron@hybridgroup.com>
---
 src/machine/i2c.go                    | 11 ++++++
 src/machine/machine_atmega.go         |  6 ++++
 src/machine/machine_atsamd21.go       |  5 +--
 src/machine/machine_atsamd51.go       |  5 +--
 src/machine/machine_fe310.go          |  6 ++++
 src/machine/machine_generic.go        |  9 +++++
 src/machine/machine_k210.go           |  6 ++++
 src/machine/machine_mimxrt1062_i2c.go |  6 ++++
 src/machine/machine_nrf.go            | 48 +++++++++++++++++++++++++++
 src/machine/machine_stm32_i2c_reva.go |  6 ++++
 src/machine/machine_stm32_i2c_revb.go |  6 ++++
 11 files changed, 110 insertions(+), 4 deletions(-)

diff --git a/src/machine/i2c.go b/src/machine/i2c.go
index c8bd6d1b4f..384d3deed0 100644
--- a/src/machine/i2c.go
+++ b/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.
diff --git a/src/machine/machine_atmega.go b/src/machine/machine_atmega.go
index 81a47c0dfa..d60b141476 100644
--- a/src/machine/machine_atmega.go
+++ b/src/machine/machine_atmega.go
@@ -46,6 +46,12 @@ 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
+}
+
 // Tx does a single I2C transaction at the specified address.
 // It clocks out the given address, writes the bytes in w, reads back len(r)
 // bytes and stores them in r, and generates a stop condition on the bus.
diff --git a/src/machine/machine_atsamd21.go b/src/machine/machine_atsamd21.go
index 443c7af56a..3ad93dccf0 100644
--- a/src/machine/machine_atsamd21.go
+++ b/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.
diff --git a/src/machine/machine_atsamd51.go b/src/machine/machine_atsamd51.go
index 8d37f2fa5f..bdc00c9aff 100644
--- a/src/machine/machine_atsamd51.go
+++ b/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.
diff --git a/src/machine/machine_fe310.go b/src/machine/machine_fe310.go
index 85a2c5bd37..024e156f13 100644
--- a/src/machine/machine_fe310.go
+++ b/src/machine/machine_fe310.go
@@ -259,6 +259,12 @@ 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
+}
+
 // Tx does a single I2C transaction at the specified address.
 // It clocks out the given address, writes the bytes in w, reads back len(r)
 // bytes and stores them in r, and generates a stop condition on the bus.
diff --git a/src/machine/machine_generic.go b/src/machine/machine_generic.go
index b0aea80621..3b1f059389 100644
--- a/src/machine/machine_generic.go
+++ b/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
 
diff --git a/src/machine/machine_k210.go b/src/machine/machine_k210.go
index e8a304c850..9188cf54e0 100644
--- a/src/machine/machine_k210.go
+++ b/src/machine/machine_k210.go
@@ -582,6 +582,12 @@ 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
+}
+
 // Tx does a single I2C transaction at the specified address.
 // It clocks out the given address, writes the bytes in w, reads back len(r)
 // bytes and stores them in r, and generates a stop condition on the bus.
diff --git a/src/machine/machine_mimxrt1062_i2c.go b/src/machine/machine_mimxrt1062_i2c.go
index d7ba82f558..8531eba1db 100644
--- a/src/machine/machine_mimxrt1062_i2c.go
+++ b/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 {
diff --git a/src/machine/machine_nrf.go b/src/machine/machine_nrf.go
index d7b87d9aec..cbf013304d 100644
--- a/src/machine/machine_nrf.go
+++ b/src/machine/machine_nrf.go
@@ -205,6 +205,20 @@ func (uart *UART) handleInterrupt(interrupt.Interrupt) {
 
 const i2cTimeout = 0xffff // this is around 29ms on a nrf52
 
+// check for ensuring we fulfill interface
+var _ i2cController = (*I2C)(nil)
+
+// I2C on the NRF.
+type I2C struct {
+	Bus nrf.TWI_Type
+}
+
+// There are 2 I2C interfaces on the NRF.
+var (
+	I2C0 = (*I2C)(unsafe.Pointer(nrf.TWI0))
+	I2C1 = (*I2C)(unsafe.Pointer(nrf.TWI1))
+)
+
 // I2CConfig is used to store config info for I2C.
 type I2CConfig struct {
 	Frequency uint32
@@ -246,6 +260,40 @@ func (i2c *I2C) Configure(config I2CConfig) error {
 	i2c.setPins(config.SCL, config.SDA)
 
 	i2c.mode = config.Mode
+	i2c.Bus.ENABLE.Set(nrf.TWI_ENABLE_ENABLE_Enabled)
+
+	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 {
+	// TODO: implement
+	return nil
+}
+
+// Tx does a single I2C transaction at the specified address.
+// It clocks out the given address, writes the bytes in w, reads back len(r)
+// bytes and stores them in r, and generates a stop condition on the bus.
+func (i2c *I2C) Tx(addr uint16, w, r []byte) (err error) {
+
+	// Tricky stop condition.
+	// After reads, the stop condition is generated implicitly with a shortcut.
+	// After writes not followed by reads and in the case of errors, stop must be generated explicitly.
+
+	i2c.Bus.ADDRESS.Set(uint32(addr))
+
+	if len(w) != 0 {
+		i2c.Bus.TASKS_STARTTX.Set(1) // start transmission for writing
+		for _, b := range w {
+			if err = i2c.writeByte(b); err != nil {
+				i2c.signalStop()
+				return
+			}
+		}
+	}
 
 	if i2c.mode == I2CModeController {
 		if config.Frequency >= 400*KHz {
diff --git a/src/machine/machine_stm32_i2c_reva.go b/src/machine/machine_stm32_i2c_reva.go
index 38ebdcdc42..0dea71639b 100644
--- a/src/machine/machine_stm32_i2c_reva.go
+++ b/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 {
diff --git a/src/machine/machine_stm32_i2c_revb.go b/src/machine/machine_stm32_i2c_revb.go
index 6adb704dbd..24ba8aec9d 100644
--- a/src/machine/machine_stm32_i2c_revb.go
+++ b/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 {

From 3541fcc1b26b912a043867b033c53ad26d63e48f Mon Sep 17 00:00:00 2001
From: deadprogram <ron@hybridgroup.com>
Date: Mon, 3 Jul 2023 13:21:31 +0200
Subject: [PATCH 2/8] machine/nrf: updates for i2c interface testing

Signed-off-by: deadprogram <ron@hybridgroup.com>
---
 src/machine/machine_nrf.go   | 59 ------------------------------------
 src/machine/machine_nrf5x.go |  9 ++++++
 2 files changed, 9 insertions(+), 59 deletions(-)

diff --git a/src/machine/machine_nrf.go b/src/machine/machine_nrf.go
index cbf013304d..1256319fe9 100644
--- a/src/machine/machine_nrf.go
+++ b/src/machine/machine_nrf.go
@@ -205,20 +205,6 @@ func (uart *UART) handleInterrupt(interrupt.Interrupt) {
 
 const i2cTimeout = 0xffff // this is around 29ms on a nrf52
 
-// check for ensuring we fulfill interface
-var _ i2cController = (*I2C)(nil)
-
-// I2C on the NRF.
-type I2C struct {
-	Bus nrf.TWI_Type
-}
-
-// There are 2 I2C interfaces on the NRF.
-var (
-	I2C0 = (*I2C)(unsafe.Pointer(nrf.TWI0))
-	I2C1 = (*I2C)(unsafe.Pointer(nrf.TWI1))
-)
-
 // I2CConfig is used to store config info for I2C.
 type I2CConfig struct {
 	Frequency uint32
@@ -265,51 +251,6 @@ 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 {
-	// TODO: implement
-	return nil
-}
-
-// Tx does a single I2C transaction at the specified address.
-// It clocks out the given address, writes the bytes in w, reads back len(r)
-// bytes and stores them in r, and generates a stop condition on the bus.
-func (i2c *I2C) Tx(addr uint16, w, r []byte) (err error) {
-
-	// Tricky stop condition.
-	// After reads, the stop condition is generated implicitly with a shortcut.
-	// After writes not followed by reads and in the case of errors, stop must be generated explicitly.
-
-	i2c.Bus.ADDRESS.Set(uint32(addr))
-
-	if len(w) != 0 {
-		i2c.Bus.TASKS_STARTTX.Set(1) // start transmission for writing
-		for _, b := range w {
-			if err = i2c.writeByte(b); err != nil {
-				i2c.signalStop()
-				return
-			}
-		}
-	}
-
-	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.enableAsController()
-	} else {
-		i2c.enableAsTarget()
-	}
-
-	return nil
-}
-
 // signalStop sends a stop signal to the I2C peripheral and waits for confirmation.
 func (i2c *I2C) signalStop() error {
 	tries := 0
diff --git a/src/machine/machine_nrf5x.go b/src/machine/machine_nrf5x.go
index 4c731036be..cbe0a7d077 100644
--- a/src/machine/machine_nrf5x.go
+++ b/src/machine/machine_nrf5x.go
@@ -28,6 +28,15 @@ func (i2c *I2C) disable() {
 	i2c.Bus.ENABLE.Set(0)
 }
 
+// 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 {
+	// TODO: implement
+	return nil
+}
+
 // Tx does a single I2C transaction at the specified address.
 // It clocks out the given address, writes the bytes in w, reads back len(r)
 // bytes and stores them in r, and generates a stop condition on the bus.

From 5c75fbe6b1b4f7908b765d5136b2114f092dd852 Mon Sep 17 00:00:00 2001
From: deadprogram <ron@hybridgroup.com>
Date: Wed, 11 Oct 2023 21:24:59 +0200
Subject: [PATCH 3/8] machine/atmega: implement i2c.SetBaudRate()

Signed-off-by: deadprogram <ron@hybridgroup.com>
---
 src/machine/machine_atmega.go | 13 ++++++-------
 1 file changed, 6 insertions(+), 7 deletions(-)

diff --git a/src/machine/machine_atmega.go b/src/machine/machine_atmega.go
index d60b141476..c5d56b0316 100644
--- a/src/machine/machine_atmega.go
+++ b/src/machine/machine_atmega.go
@@ -31,6 +31,11 @@ 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))
 
@@ -38,7 +43,7 @@ func (i2c *I2C) Configure(config I2CConfig) error {
 	// 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)
@@ -46,12 +51,6 @@ 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
-}
-
 // Tx does a single I2C transaction at the specified address.
 // It clocks out the given address, writes the bytes in w, reads back len(r)
 // bytes and stores them in r, and generates a stop condition on the bus.

From 1ea9c7f815c7dc1ec2e009246e6d4b4f6e42cdff Mon Sep 17 00:00:00 2001
From: deadprogram <ron@hybridgroup.com>
Date: Wed, 11 Oct 2023 21:25:21 +0200
Subject: [PATCH 4/8] machine/fe310: implement i2c.SetBaudRate()

Signed-off-by: deadprogram <ron@hybridgroup.com>
---
 src/machine/machine_fe310.go | 24 +++++++++++++-----------
 1 file changed, 13 insertions(+), 11 deletions(-)

diff --git a/src/machine/machine_fe310.go b/src/machine/machine_fe310.go
index 024e156f13..37f3ee07e8 100644
--- a/src/machine/machine_fe310.go
+++ b/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)
@@ -253,15 +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
-}
-
-// SetBaudRate sets the communication speed for I2C.
-func (i2c *I2C) SetBaudRate(br uint32) error {
-	// TODO: implement
 	return nil
 }
 

From c618119e92338888d31c163a7d8b487bc80faf52 Mon Sep 17 00:00:00 2001
From: deadprogram <ron@hybridgroup.com>
Date: Wed, 11 Oct 2023 21:25:44 +0200
Subject: [PATCH 5/8] machine/k210: implement i2c.SetBaudRate()

Signed-off-by: deadprogram <ron@hybridgroup.com>
---
 src/machine/machine_k210.go | 23 ++++++++++++-----------
 1 file changed, 12 insertions(+), 11 deletions(-)

diff --git a/src/machine/machine_k210.go b/src/machine/machine_k210.go
index 9188cf54e0..e0821670ba 100644
--- a/src/machine/machine_k210.go
+++ b/src/machine/machine_k210.go
@@ -563,16 +563,7 @@ func (i2c *I2C) Configure(config I2CConfig) error {
 		config.SCL.SetFPIOAFunction(FUNC_I2C2_SCLK)
 	}
 
-	div := CPUFrequency() / config.Frequency / 16
-
-	// Disable controller before setting the prescale register.
-	i2c.Bus.ENABLE.Set(0)
-
-	i2c.Bus.CON.Set(0x63)
-
-	// Set prescaler registers.
-	i2c.Bus.SS_SCL_HCNT.Set(uint32(div))
-	i2c.Bus.SS_SCL_LCNT.Set(uint32(div))
+	i2c.SetBaudRate(config.Frequency)
 
 	i2c.Bus.INTR_MASK.Set(0)
 	i2c.Bus.DMA_CR.Set(0x03)
@@ -584,7 +575,17 @@ func (i2c *I2C) Configure(config I2CConfig) error {
 
 // SetBaudRate sets the communication speed for I2C.
 func (i2c *I2C) SetBaudRate(br uint32) error {
-	// TODO: implement
+	div := CPUFrequency() / br / 16
+
+	// Disable controller before setting the prescale register.
+	i2c.Bus.ENABLE.Set(0)
+
+	i2c.Bus.CON.Set(0x63)
+
+	// Set prescaler registers.
+	i2c.Bus.SS_SCL_HCNT.Set(uint32(div))
+	i2c.Bus.SS_SCL_LCNT.Set(uint32(div))
+
 	return nil
 }
 

From 756fe3b62945e0971f9566692215755ceeec1c81 Mon Sep 17 00:00:00 2001
From: deadprogram <ron@hybridgroup.com>
Date: Wed, 11 Oct 2023 21:26:09 +0200
Subject: [PATCH 6/8] machine/nrf: implement i2c.SetBaudRate()

Signed-off-by: deadprogram <ron@hybridgroup.com>
---
 src/machine/machine_nrf.go   | 25 ++++++++++++++++++++++++-
 src/machine/machine_nrf5x.go |  9 ---------
 2 files changed, 24 insertions(+), 10 deletions(-)

diff --git a/src/machine/machine_nrf.go b/src/machine/machine_nrf.go
index 1256319fe9..3b79e376a3 100644
--- a/src/machine/machine_nrf.go
+++ b/src/machine/machine_nrf.go
@@ -246,7 +246,30 @@ func (i2c *I2C) Configure(config I2CConfig) error {
 	i2c.setPins(config.SCL, config.SDA)
 
 	i2c.mode = config.Mode
-	i2c.Bus.ENABLE.Set(nrf.TWI_ENABLE_ENABLE_Enabled)
+	if i2c.mode == I2CModeController {
+		i2c.SetBaudRate(config.Frequency)
+
+		i2c.enableAsController()
+	} else {
+		i2c.enableAsTarget()
+	}
+
+	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
 }
diff --git a/src/machine/machine_nrf5x.go b/src/machine/machine_nrf5x.go
index cbe0a7d077..4c731036be 100644
--- a/src/machine/machine_nrf5x.go
+++ b/src/machine/machine_nrf5x.go
@@ -28,15 +28,6 @@ func (i2c *I2C) disable() {
 	i2c.Bus.ENABLE.Set(0)
 }
 
-// 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 {
-	// TODO: implement
-	return nil
-}
-
 // Tx does a single I2C transaction at the specified address.
 // It clocks out the given address, writes the bytes in w, reads back len(r)
 // bytes and stores them in r, and generates a stop condition on the bus.

From be73c666dcb3c11bbeb6d76656bd18715fb041e8 Mon Sep 17 00:00:00 2001
From: deadprogram <ron@hybridgroup.com>
Date: Fri, 13 Oct 2023 19:39:01 +0200
Subject: [PATCH 7/8] machine/i2c: return error when calling not yet
 implemented SetBaudRate() function

Signed-off-by: deadprogram <ron@hybridgroup.com>
---
 src/machine/i2c.go                    | 1 +
 src/machine/machine_mimxrt1062_i2c.go | 2 +-
 src/machine/machine_stm32_i2c_reva.go | 2 +-
 src/machine/machine_stm32_i2c_revb.go | 2 +-
 4 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/src/machine/i2c.go b/src/machine/i2c.go
index 384d3deed0..434b91ee35 100644
--- a/src/machine/i2c.go
+++ b/src/machine/i2c.go
@@ -36,6 +36,7 @@ var (
 	errI2CBusError           = errors.New("I2C bus error")
 	errI2COverflow           = errors.New("I2C receive buffer overflow")
 	errI2COverread           = errors.New("I2C transmit buffer overflow")
+	errI2CNotImplemented     = errors.New("I2C operation not yet implemented")
 )
 
 // I2CTargetEvent reflects events on the I2C bus
diff --git a/src/machine/machine_mimxrt1062_i2c.go b/src/machine/machine_mimxrt1062_i2c.go
index 8531eba1db..ee46ff9569 100644
--- a/src/machine/machine_mimxrt1062_i2c.go
+++ b/src/machine/machine_mimxrt1062_i2c.go
@@ -174,7 +174,7 @@ func (i2c *I2C) Configure(config I2CConfig) {
 // SetBaudRate sets the communication speed for I2C.
 func (i2c I2C) SetBaudRate(br uint32) error {
 	// TODO: implement
-	return nil
+	return errI2CNotImplemented
 }
 
 func (i2c I2C) Tx(addr uint16, w, r []byte) error {
diff --git a/src/machine/machine_stm32_i2c_reva.go b/src/machine/machine_stm32_i2c_reva.go
index 0dea71639b..1e4fd282e9 100644
--- a/src/machine/machine_stm32_i2c_reva.go
+++ b/src/machine/machine_stm32_i2c_reva.go
@@ -160,7 +160,7 @@ func (i2c *I2C) Configure(config I2CConfig) error {
 // SetBaudRate sets the communication speed for I2C.
 func (i2c *I2C) SetBaudRate(br uint32) error {
 	// TODO: implement
-	return nil
+	return errI2CNotImplemented
 }
 
 func (i2c *I2C) Tx(addr uint16, w, r []byte) error {
diff --git a/src/machine/machine_stm32_i2c_revb.go b/src/machine/machine_stm32_i2c_revb.go
index 24ba8aec9d..9253902940 100644
--- a/src/machine/machine_stm32_i2c_revb.go
+++ b/src/machine/machine_stm32_i2c_revb.go
@@ -87,7 +87,7 @@ func (i2c *I2C) Configure(config I2CConfig) error {
 // SetBaudRate sets the communication speed for I2C.
 func (i2c *I2C) SetBaudRate(br uint32) error {
 	// TODO: implement
-	return nil
+	return errI2CNotImplemented
 }
 
 func (i2c *I2C) Tx(addr uint16, w, r []byte) error {

From e7dbb0a69739e2d541a90bbff986b9ef365aac88 Mon Sep 17 00:00:00 2001
From: deadprogram <ron@hybridgroup.com>
Date: Fri, 13 Oct 2023 20:03:16 +0200
Subject: [PATCH 8/8] machine/mimxrt1062: ensure that conforms to the i2c
 interface, moves the extended register functions to different name to avoid
 naming clash

Signed-off-by: deadprogram <ron@hybridgroup.com>
---
 src/machine/i2c.go                    |  2 +-
 src/machine/machine_mimxrt1062_i2c.go | 27 ++++++++-------------------
 2 files changed, 9 insertions(+), 20 deletions(-)

diff --git a/src/machine/i2c.go b/src/machine/i2c.go
index 434b91ee35..5fdf2d5266 100644
--- a/src/machine/i2c.go
+++ b/src/machine/i2c.go
@@ -1,4 +1,4 @@
-//go:build atmega || nrf || sam || stm32 || fe310 || k210 || rp2040
+//go:build atmega || nrf || sam || stm32 || fe310 || k210 || rp2040 || mimxrt1062
 
 package machine
 
diff --git a/src/machine/machine_mimxrt1062_i2c.go b/src/machine/machine_mimxrt1062_i2c.go
index ee46ff9569..f3c4636178 100644
--- a/src/machine/machine_mimxrt1062_i2c.go
+++ b/src/machine/machine_mimxrt1062_i2c.go
@@ -6,19 +6,6 @@ package machine
 
 import (
 	"device/nxp"
-	"errors"
-)
-
-var (
-	errI2CWriteTimeout       = errors.New("I2C timeout during write")
-	errI2CReadTimeout        = errors.New("I2C timeout during read")
-	errI2CBusReadyTimeout    = errors.New("I2C timeout on bus ready")
-	errI2CSignalStartTimeout = errors.New("I2C timeout on signal start")
-	errI2CSignalReadTimeout  = errors.New("I2C timeout on signal read")
-	errI2CSignalStopTimeout  = errors.New("I2C timeout on signal stop")
-	errI2CAckExpected        = errors.New("I2C error: expected ACK not NACK")
-	errI2CBusError           = errors.New("I2C bus error")
-	errI2CNotConfigured      = errors.New("I2C interface is not yet configured")
 )
 
 // I2CConfig is used to store config info for I2C.
@@ -150,7 +137,7 @@ func (i2c *I2C) setPins(c I2CConfig) (sda, scl Pin) {
 }
 
 // Configure is intended to setup an I2C interface for transmit/receive.
-func (i2c *I2C) Configure(config I2CConfig) {
+func (i2c *I2C) Configure(config I2CConfig) error {
 	// init pins
 	sda, scl := i2c.setPins(config)
 
@@ -169,6 +156,8 @@ func (i2c *I2C) Configure(config I2CConfig) {
 
 	// reset clock and registers, and enable LPI2C module interface
 	i2c.reset(freq)
+
+	return nil
 }
 
 // SetBaudRate sets the communication speed for I2C.
@@ -218,13 +207,13 @@ func (i2c I2C) Tx(addr uint16, w, r []byte) error {
 	return nil
 }
 
-// WriteRegister transmits first the register and then the data to the
+// WriteRegisterEx transmits first the register and then the data to the
 // peripheral device.
 //
 // Many I2C-compatible devices are organized in terms of registers. This method
 // is a shortcut to easily write to such registers. Also, it only works for
 // devices with 7-bit addresses, which is the vast majority.
-func (i2c I2C) WriteRegister(address uint8, register uint8, data []byte) error {
+func (i2c I2C) WriteRegisterEx(address uint8, register uint8, data []byte) error {
 	option := transferOption{
 		flags:          transferDefault,  // transfer options bit mask (0 = normal transfer)
 		peripheral:     uint16(address),  // 7-bit peripheral address
@@ -238,13 +227,13 @@ func (i2c I2C) WriteRegister(address uint8, register uint8, data []byte) error {
 	return nil
 }
 
-// ReadRegister transmits the register, restarts the connection as a read
+// ReadRegisterEx transmits the register, restarts the connection as a read
 // operation, and reads the response.
 //
 // Many I2C-compatible devices are organized in terms of registers. This method
 // is a shortcut to easily read such registers. Also, it only works for devices
 // with 7-bit addresses, which is the vast majority.
-func (i2c I2C) ReadRegister(address uint8, register uint8, data []byte) error {
+func (i2c I2C) ReadRegisterEx(address uint8, register uint8, data []byte) error {
 	option := transferOption{
 		flags:          transferDefault,  // transfer options bit mask (0 = normal transfer)
 		peripheral:     uint16(address),  // 7-bit peripheral address
@@ -566,7 +555,7 @@ func (i2c *I2C) controllerReceive(rxBuffer []byte) resultFlag {
 	return result
 }
 
-// controllerReceive performs a polling transmit transfer on the I2C bus.
+// controllerTransmit performs a polling transmit transfer on the I2C bus.
 func (i2c *I2C) controllerTransmit(txBuffer []byte) resultFlag {
 	txSize := len(txBuffer)
 	for txSize > 0 {