i2csoft: use cycle counting for delays

This should make the software I2C driver more portable, and potentially
usable on chips that aren't yet supported. More importantly, it avoids
some guesswork in the various chip-specific timing code.

Author: aykevl

i2csoft/i2csoft.go

@@ -3,6 +3,9 @@ package i2csoft
 import (
 	"errors"
 	"machine"
+	"time"
+
+	"tinygo.org/x/drivers/delay"
 )
 
 // I2C is an I2C implementation by Software. Since it is implemented by
@@ -278,3 +281,8 @@ func (i2c *I2C) WriteRegister(address uint8, register uint8, data []byte) error
 func (i2c *I2C) ReadRegister(address uint8, register uint8, data []byte) error {
 	return i2c.Tx(uint16(address), []byte{register}, data)
 }
+
+// wait waits for half the time of the SCL operation interval.
+func (i2c *I2C) wait() {
+	delay.Sleep(50 * time.Microsecond) // half of a 100kHz cycle (50µs)
+}