Drop I2C bit functions, to make timing easier to modify

I2C to the charger now has clean 100kHz timing. One read command now takes
400us, and one write command takes 300us to execute.

firmware/main.c

@@ -1006,7 +1006,7 @@ static __bit poll_scl_busy(void)
 }
 */
 
-void i2c_start_condition(void)
+static void i2c_start_condition(void)
 {
 	CHG_RELEASE_SDA;
 	delay_us(5);
@@ -1021,7 +1021,7 @@ void i2c_start_condition(void)
 	delay_us(5);
 }
 
-void i2c_stop_condition(void)
+static void i2c_stop_condition(void)
 {
 	CHG_PULL_SDA;
 	delay_us(5);
@@ -1033,68 +1033,78 @@ void i2c_stop_condition(void)
 	delay_us(5);
 }
 
-void i2c_write_bit(__bit b)
+static __bit i2c_write_byte(uint8_t data)
 {
-	if (b)
-		CHG_RELEASE_SDA;
-	else
-		CHG_PULL_SDA;
-	delay_us(1);
+	uint8_t i;
+	__bit ack = 1;
 
-	CHG_RELEASE_SCL;
-	delay_us(5);
+	// write data
+	for (i = 0; i < 8; i++) {
+		// write the most-significant bit
+		if (data & 0x80)
+			CHG_RELEASE_SDA;
+		else
+			CHG_PULL_SDA;
+		delay_us(1);
 
-	CHG_PULL_SCL;
-	delay_us(1);
-}
+		CHG_RELEASE_SCL;
+		delay_us(5);
 
-__bit i2c_read_bit(void)
-{
-	__bit b;
+		CHG_PULL_SCL;
+		delay_us(1);
 
-	CHG_RELEASE_SDA;
+		data <<= 1;
+	}
+
+	delay_us(1);
 
+	// read ack bit
+	CHG_RELEASE_SDA;
 	CHG_RELEASE_SCL;
-	delay_us(4);
+	delay_us(3);
 
 	if (CHG_PORT & CHG_SDA)
-		b = 1;
-	else
-		b = 0;
+		ack = 0;
 
 	CHG_PULL_SCL;
 	delay_us(2);
 
-	return b;
+	return ack;
 }
 
-__bit i2c_write_byte(uint8_t data)
+static uint8_t i2c_read_byte(__bit ack)
 {
+	uint8_t data = 0;
 	uint8_t i;
 
-	// write data
+	CHG_RELEASE_SDA;
+
+	// read data
 	for (i = 0; i < 8; i++) {
-		i2c_write_bit(data & 0x80);   // write the most-significant bit
 		data <<= 1;
-	}
 
-	// read ack bit
-	return !i2c_read_bit();
-}
+		CHG_RELEASE_SCL;
+		delay_us(4);
 
-uint8_t i2c_read_byte(__bit ack)
-{
-	uint8_t data = 0;
-	uint8_t i;
+		if (CHG_PORT & CHG_SDA)
+			data |= 1;
 
-	// read data
-	for (i = 0; i < 8; i++) {
-		data <<= 1;
-		data |= i2c_read_bit();
+		CHG_PULL_SCL;
+		delay_us(2);
 	}
 
 	// send ack
-	i2c_write_bit(!ack);
+	if (ack)
+		CHG_PULL_SDA;
+	else
+		CHG_RELEASE_SDA;
+	delay_us(1);
+
+	CHG_RELEASE_SCL;
+	delay_us(5);
+
+	CHG_PULL_SCL;
+	delay_us(1);
 	return data;
 }
 

i2c-charger-ctl.c

@@ -130,7 +130,7 @@ uint8_t read_power(int fd, uint8_t reg)
 	syscall_error(ret < 0, "I2C_RDWR failed");
 
 	for (int i = 0; i < 5; i++) {
-		usleep(2000);
+		usleep(700);
 
 		// read the result
 		uint8_t buf2[1] = { REG_SYS_CHG_DATA, };
@@ -183,7 +183,7 @@ void write_power(int fd, uint8_t reg, uint8_t val)
 	syscall_error(ret < 0, "I2C_RDWR failed");
 
 	for (int i = 0; i < 5; i++) {
-		usleep(2000);
+		usleep(700);
 
 		// read the result
 		uint8_t buf2[1] = { REG_SYS_COMMAND, };