i2csoft: add source code for each target

i2csoft/i2csoft_atsamd51.go

@@ -4,20 +4,14 @@
 package i2csoft
 
 import (
-	"device/arm"
+	"device"
 )
 
+// wait waits for half the time of the SCL operation interval. It is set to
+// about 100 kHz.
 func (i2c *I2C) wait() {
-	// atsamd51
-	//  1 : about 388kHz
-	// 17 : about 97kHz
-
-	wait := 1
-	if i2c.baudrate < 400*1e3 {
-		wait = 17
-	}
-
+	wait := 20
 	for i := 0; i < wait; i++ {
-		arm.Asm(`nop`)
+		device.Asm(`nop`)
 	}
 }

i2csoft/i2csoft_esp32.go

@@ -7,16 +7,10 @@ import (
 	"device"
 )
 
+// wait waits for half the time of the SCL operation interval. It is set to
+// about 100 kHz.
 func (i2c *I2C) wait() {
-	// atsamd51
-	// 10 : about 387kHz
-	// 56 : about 99kHz
-
-	wait := 10
-	if i2c.baudrate < 400*1e3 {
-		wait = 56
-	}
-
+	wait := 60
 	for i := 0; i < wait; i++ {
 		device.Asm(`nop`)
 	}

i2csoft/i2csoft_nrf52840.go

@@ -0,0 +1,17 @@
+//go:build nrf52840
+// +build nrf52840
+
+package i2csoft
+
+import (
+	"device"
+)
+
+// wait waits for half the time of the SCL operation interval. It is set to
+// about 100 kHz.
+func (i2c *I2C) wait() {
+	wait := 26
+	for i := 0; i < wait; i++ {
+		device.Asm(`nop`)
+	}
+}

i2csoft/i2csoft_other.go

@@ -1,5 +1,5 @@
-//go:build !esp32 && !atsamd51 && !atsame5x
-// +build !esp32,!atsamd51,!atsame5x
+//go:build !esp32 && !atsamd51 && !atsame5x && !stm32f4 && !rp2040 && ! nrf52840
+// +build !esp32,!atsamd51,!atsame5x,!stm32f4,!rp2040,!nrf52840
 
 package i2csoft
 
@@ -7,15 +7,9 @@ import (
 	"device"
 )
 
+// wait waits for half the time of the SCL operation interval.
 func (i2c *I2C) wait() {
-	// atsamd21 @ 48MHz
-	//  1 : about 360kHz
-	// 24 : about 96kHz
-	wait := 1
-	if i2c.baudrate < 400*1e3 {
-		wait = 19
-	}
-
+	wait := 20
 	for i := 0; i < wait; i++ {
 		device.Asm(`nop`)
 	}

i2csoft/i2csoft_rp2040.go

@@ -0,0 +1,17 @@
+//go:build rp2040
+// +build rp2040
+
+package i2csoft
+
+import (
+	"device"
+)
+
+// wait waits for half the time of the SCL operation interval. It is set to
+// about 100 kHz.
+func (i2c *I2C) wait() {
+	wait := 50
+	for i := 0; i < wait; i++ {
+		device.Asm(`nop`)
+	}
+}

i2csoft/i2csoft_stm32f4.go

@@ -0,0 +1,17 @@
+//go:build stm32f4
+// +build stm32f4
+
+package i2csoft
+
+import (
+	"device"
+)
+
+// wait waits for half the time of the SCL operation interval. It is set to
+// about 100 kHz.
+func (i2c *I2C) wait() {
+	wait := 77
+	for i := 0; i < wait; i++ {
+		device.Asm(`nop`)
+	}
+}