diff --git a/lib/rtc_ds1307.c b/lib/rtc_ds1307.c
index aff5071..3ca51f8 100644
--- a/lib/rtc_ds1307.c
+++ b/lib/rtc_ds1307.c
@@ -16,7 +16,7 @@
  *  @file rtc_ds1307.c
  *  @author King Kévin <kingkevin@cuvoodoo.info>
  *  @date 2016-2017
- *  @note peripherals used: I2C @ref rtc_ds1307_i2c
+ *  @note peripherals used: I2C @ref i2c_i2c
  */
 
 /* standard libraries */
@@ -31,87 +31,21 @@
 
 #include "global.h" // global utilities
 #include "rtc_ds1307.h" // RTC header and definitions
+#include "i2c.h" // i2c utilities
 
-/** @defgroup rtc_ds1307_i2c I2C peripheral used to communicate with DS1307 RTC IC
- *  @{
- */
-/** I2C peripheral */
-#define RTC_DS1307_I2C 2 /**< I2C peripheral */
 #define RTC_DS1307_I2C_ADDR 0x68 /**< DS1307 I2C address (fixed to 0b1101000) */
-/** @} */
 
 void rtc_ds1307_setup(void)
 {
 	// configure I2C peripheral
-	rcc_periph_clock_enable(RCC_I2C_SCL_PORT(RTC_DS1307_I2C)); // enable clock for I2C I/O peripheral
-	gpio_set_mode(I2C_SCL_PORT(RTC_DS1307_I2C), GPIO_MODE_OUTPUT_2_MHZ, GPIO_CNF_OUTPUT_ALTFN_OPENDRAIN, I2C_SCL_PIN(RTC_DS1307_I2C)); // setup I2C I/O pins
-	rcc_periph_clock_enable(RCC_I2C_SCL_PORT(RTC_DS1307_I2C)); // enable clock for I2C I/O peripheral
-    gpio_set_mode(I2C_SDA_PORT(RTC_DS1307_I2C), GPIO_MODE_OUTPUT_2_MHZ, GPIO_CNF_OUTPUT_ALTFN_OPENDRAIN, I2C_SDA_PIN(RTC_DS1307_I2C)); // setup I2C I/O pins
-	rcc_periph_clock_enable(RCC_AFIO); // enable clock for alternate function
-	rcc_periph_clock_enable(RCC_I2C(RTC_DS1307_I2C)); // enable clock for I2C peripheral
-	i2c_reset(I2C(RTC_DS1307_I2C)); // reset configuration
-	i2c_peripheral_disable(I2C(RTC_DS1307_I2C)); // I2C needs to be disable to be configured
-	i2c_set_clock_frequency(I2C(RTC_DS1307_I2C), rcc_apb1_frequency/1000000); // configure the peripheral clock to the APB1 freq (where it is connected to)
-	i2c_set_standard_mode(I2C(RTC_DS1307_I2C)); // the DS1307 has a maximum I2C SCL freq if 100 kHz (corresponding to the standard mode)
-	i2c_set_ccr(I2C(RTC_DS1307_I2C), rcc_apb1_frequency/(100000*2)); // set Thigh/Tlow to generate frequency of 100 kHz
-	i2c_set_trise(I2C(RTC_DS1307_I2C), rcc_apb1_frequency/1000000); // max rise time for 100 kHz is 1000 ns (~1 MHz)
-	i2c_peripheral_enable(I2C(RTC_DS1307_I2C)); // enable I2C after configuration completed
-}
-
-/** read memory from RTC IC
- *  @param[in] addr start address for memory to read
- *  @param[out] data buffer to store read memory
- *  @param[in] len number of byte to read from the memory
- *  @return if read succeeded
- */
-static bool rtc_ds1307_read_memory(uint8_t addr, uint8_t* data, size_t len)
-{
-	bool to_return = false; // return if read succeeded
-	if (data==NULL || len==0) { // verify there it data to be read
-		goto error;
-	}
-	i2c_send_start(I2C(RTC_DS1307_I2C)); // send start condition to start transaction
-	while (!(I2C_SR1(I2C(RTC_DS1307_I2C)) & I2C_SR1_SB)); // wait until start condition is transmitted
-	if (!(I2C_SR2(I2C(RTC_DS1307_I2C)) & I2C_SR2_MSL)) { // verify if in master mode
-		goto error;
-	}
-	i2c_send_7bit_address(I2C(RTC_DS1307_I2C), RTC_DS1307_I2C_ADDR, I2C_WRITE); // select slave
-	while (!(I2C_SR1(I2C(RTC_DS1307_I2C)) & I2C_SR1_ADDR)); // wait until address is transmitted
-	if (!((I2C_SR2(I2C(RTC_DS1307_I2C)) & I2C_SR2_TRA))) { // verify we are in transmit mode (and read SR2 to clear ADDR)
-		goto error;
-	}
-	i2c_send_data(I2C(RTC_DS1307_I2C), addr); // send memory address we want to read
-	while (!(I2C_SR1(I2C(RTC_DS1307_I2C)) & I2C_SR1_TxE)); // wait until byte has been transmitted
-	i2c_send_start(I2C(RTC_DS1307_I2C)); // send restart condition to switch from write to read mode
-	while (!(I2C_SR1(I2C(RTC_DS1307_I2C)) & I2C_SR1_SB)); // wait until start condition is transmitted
-	i2c_send_7bit_address(I2C(RTC_DS1307_I2C), RTC_DS1307_I2C_ADDR, I2C_READ); // select slave
-	while (!(I2C_SR1(I2C(RTC_DS1307_I2C)) & I2C_SR1_ADDR)); // wait until address is transmitted
-	if ((I2C_SR2(I2C(RTC_DS1307_I2C)) & I2C_SR2_TRA)) { // verify we are in read mode (and read SR2 to clear ADDR)
-		goto error;
-	}
-	for (size_t i=0; i<len; i++) { // read bytes
-		if (i==len-1) { // prepare to sent NACK for last byte
-			i2c_disable_ack(I2C(RTC_DS1307_I2C)); // NACK received to stop slave transmission
-			i2c_send_stop(I2C(RTC_DS1307_I2C)); // send STOP after receiving byte
-		} else {
-			i2c_enable_ack(I2C(RTC_DS1307_I2C)); // ACK received byte to continue slave transmission
-		}
-		while (!(I2C_SR1(I2C(RTC_DS1307_I2C)) & I2C_SR1_RxNE)); // wait until byte has been received
-		data[i] = i2c_get_data(I2C(RTC_DS1307_I2C)); // read received byte
-	}
-	to_return = true;
-error:
-	if (I2C_SR2(I2C(RTC_DS1307_I2C)) & I2C_SR2_BUSY) { // release bus if busy
-		i2c_send_stop(I2C(RTC_DS1307_I2C)); // send stop to release bus
-	}
-	while (I2C_SR2(I2C(RTC_DS1307_I2C)) & I2C_SR2_MSL); // wait until bus released (non master mode)
-	return to_return;
+	i2c_master(false); // DS1307 only supports normal mode (up to 100 kHz)
 }
 
 bool rtc_ds1307_oscillator_disabled(void)
 {
 	uint8_t data[1] = {0}; // to read data over I2C
-	rtc_ds1307_read_memory(0, data, LENGTH(data)); // read a single byte containing CH value
+	const uint8_t address[] = {0x00}; // memory address for data
+	i2c_read(RTC_DS1307_I2C_ADDR, address, LENGTH(address), data, LENGTH(data)); // read a single byte containing CH value
 	return data[0]&0x80; // return CH bit value to indicate if oscillator is disabled
 }
 
@@ -120,7 +54,8 @@ uint16_t rtc_ds1307_read_square_wave(void)
 	uint16_t to_return = 0; // square wave frequency to return (in Hz)
 	uint8_t data[1] = {0}; // to read data over I2C
 	const uint16_t rtc_ds1307_rs[] = {1, 4096, 8192, 32768}; // RS1/RS0 values
-	rtc_ds1307_read_memory(7, data, LENGTH(data)); // read a single byte containing control register
+	const uint8_t address[] = {0x07}; // memory address for data
+	i2c_read(RTC_DS1307_I2C_ADDR, address, LENGTH(address), data, LENGTH(data)); // read a single byte containing control register
 	if (data[0]&0x10) { // verify if the square wave is enabled (SQWE)
 		to_return = rtc_ds1307_rs[data[0]&0x03]; // read RS1/RS0 and get value
 	} else {
@@ -133,7 +68,8 @@ uint8_t rtc_ds1307_read_seconds(void)
 {
 	uint8_t to_return = 0; // seconds to return
 	uint8_t data[1] = {0}; // to read data over I2C
-	rtc_ds1307_read_memory(0, data, LENGTH(data)); // read a single byte containing seconds value
+	const uint8_t address[] = {0x00}; // memory address for data
+	i2c_read(RTC_DS1307_I2C_ADDR, address, LENGTH(address), data, LENGTH(data)); // read a single byte containing seconds value
 	to_return = ((data[0]&0x70)>>4)*10+(data[0]&0x0f); // convert BCD coding into seconds
 	return to_return;
 }
@@ -142,7 +78,8 @@ uint8_t rtc_ds1307_read_minutes(void)
 {
 	uint8_t to_return = 0; // minutes to return
 	uint8_t data[1] = {0}; // to read data over I2C
-	rtc_ds1307_read_memory(1, data, LENGTH(data)); // read a single byte containing minutes value
+	const uint8_t address[] = {0x01}; // memory address for data
+	i2c_read(RTC_DS1307_I2C_ADDR, address, LENGTH(address), data, LENGTH(data)); // read a single byte containing minutes value
 	to_return = (data[0]>>4)*10+(data[0]&0x0f); // convert BCD coding into minutes
 	return to_return;
 }
@@ -151,7 +88,8 @@ uint8_t rtc_ds1307_read_hours(void)
 {
 	uint8_t to_return = 0; // hours to return
 	uint8_t data[1] = {0}; // to read data over I2C
-	rtc_ds1307_read_memory(2, data, LENGTH(data)); // read a single byte containing hours value
+	const uint8_t address[] = {0x02}; // memory address for data
+	i2c_read(RTC_DS1307_I2C_ADDR, address, LENGTH(address), data, LENGTH(data)); // read a single byte containing hours value
 	if (data[0]&0x40) { // 12 hour mode
 		if (data[0]&0x02) { // PM
 			to_return += 12; // add the 12 hours
@@ -168,7 +106,8 @@ uint8_t rtc_ds1307_read_day(void)
 {
 	uint8_t to_return = 0; // day to return
 	uint8_t data[1] = {0}; // to read data over I2C
-	rtc_ds1307_read_memory(3, data, LENGTH(data)); // read a single byte containing day value
+	const uint8_t address[] = {0x03}; // memory address for data
+	i2c_read(RTC_DS1307_I2C_ADDR, address, LENGTH(address), data, LENGTH(data)); // read a single byte containing day value
 	to_return = (data[0]&0x07); // convert BCD coding into days
 	return to_return;
 }
@@ -177,7 +116,8 @@ uint8_t rtc_ds1307_read_date(void)
 {
 	uint8_t to_return = 0; // date to return
 	uint8_t data[1] = {0}; // to read data over I2C
-	rtc_ds1307_read_memory(4, data, LENGTH(data)); // read a single byte containing date value
+	const uint8_t address[] = {0x04}; // memory address for data
+	i2c_read(RTC_DS1307_I2C_ADDR, address, LENGTH(address), data, LENGTH(data)); // read a single byte containing date value
 	to_return = ((data[0]&0x30)>>4)*10+(data[0]&0x0f); // convert BCD coding into date
 	return to_return;
 }
@@ -186,7 +126,8 @@ uint8_t rtc_ds1307_read_month(void)
 {
 	uint8_t to_return = 0; // month to return
 	uint8_t data[1] = {0}; // to read data over I2C
-	rtc_ds1307_read_memory(5, data, LENGTH(data)); // read a single byte containing month value
+	const uint8_t address[] = {0x05}; // memory address for data
+	i2c_read(RTC_DS1307_I2C_ADDR, address, LENGTH(address), data, LENGTH(data)); // read a single byte containing month value
 	to_return = ((data[0]&0x10)>>4)*10+(data[0]&0x0f); // convert BCD coding into month
 	return to_return;
 }
@@ -194,7 +135,8 @@ uint8_t rtc_ds1307_read_month(void)
 uint8_t rtc_ds1307_read_year(void)
 {
 	uint8_t data[1] = {0}; // to read data over I2C
-	rtc_ds1307_read_memory(6, data, LENGTH(data)); // read a single byte containing year value
+	const uint8_t address[] = {0x06}; // memory address for data
+	i2c_read(RTC_DS1307_I2C_ADDR, address, LENGTH(address), data, LENGTH(data)); // read a single byte containing year value
 	uint8_t to_return = ((data[0]&0xf0)>>4)*10+(data[0]&0x0f); // convert BCD coding into year
 	return to_return;
 }
@@ -203,7 +145,8 @@ uint8_t* rtc_ds1307_read_time(void)
 {
 	static uint8_t time[7] = {0}; // store time {seconds, minutes, hours, day, date, month, year}
 	uint8_t data[7] = {0}; // to read data over I2C
-	rtc_ds1307_read_memory(0, data, LENGTH(data)); // read all time bytes
+	const uint8_t address[] = {0x00}; // memory address for data
+	i2c_read(RTC_DS1307_I2C_ADDR, address, LENGTH(address), data, LENGTH(data)); // read all time bytes
 	time[0] = ((data[0]&0x70)>>4)*10+(data[0]&0x0f); // convert seconds from BCD
 	time[1] = (data[1]>>4)*10+(data[1]&0x0f); // convert minutes from BCD
 	time[2] = 0; // re-initialize hours
@@ -232,60 +175,31 @@ bool rtc_ds1307_read_ram(uint8_t* data, uint8_t start, uint8_t length)
 	if (start>55 || start+length>56) { // out of bounds RAM
 		return false;
 	}
-	return rtc_ds1307_read_memory(0x08+start, data, length); // read RAM (starting at 0x08)
-}
 
-/** write memory into RTC IC
- *  @param[in] addr start address for memory to be written
- *  @param[in] data buffer to for memory to be written
- *  @param[in] len number of byte to write into the memory
- *  @return if write succeeded
- */
-static bool rtc_ds1307_write_memory(uint8_t addr, uint8_t* data, size_t len)
-{
-	bool to_return = false; // return if read succeeded
-	if (data==NULL || len==0) { // verify there it data to be read
-		goto error;
-	}
-	i2c_send_start(I2C(RTC_DS1307_I2C)); // send start condition to start transaction
-	while (!(I2C_SR1(I2C(RTC_DS1307_I2C)) & I2C_SR1_SB)); // wait until start condition is transmitted
-	if (!(I2C_SR2(I2C(RTC_DS1307_I2C)) & I2C_SR2_MSL)) { // verify if in master mode
-		goto error;
-	}
-	i2c_send_7bit_address(I2C(RTC_DS1307_I2C), RTC_DS1307_I2C_ADDR, I2C_WRITE); // select slave
-	while (!(I2C_SR1(I2C(RTC_DS1307_I2C)) & I2C_SR1_ADDR)); // wait until address is transmitted
-	if (!((I2C_SR2(I2C(RTC_DS1307_I2C)) & I2C_SR2_TRA))) { // verify we are in transmit mode (and read SR2 to clear ADDR)
-		goto error;
-	}
-	i2c_send_data(I2C(RTC_DS1307_I2C), addr); // send memory address we want to read
-	while (!(I2C_SR1(I2C(RTC_DS1307_I2C)) & I2C_SR1_TxE)); // wait until byte has been transmitted
-	for (size_t i=0; i<len; i++) { // write bytes
-		i2c_send_data(I2C(RTC_DS1307_I2C), data[i]); // send byte to be written in memory
-		while (!(I2C_SR1(I2C(RTC_DS1307_I2C)) & I2C_SR1_TxE)); // wait until byte has been transmitted
-	}
-	to_return = true;
-error:
-	if (I2C_SR2(I2C(RTC_DS1307_I2C)) & I2C_SR2_BUSY) { // release bus if busy
-		i2c_send_stop(I2C(RTC_DS1307_I2C)); // send stop to release bus
-	}
-	while (I2C_SR2(I2C(RTC_DS1307_I2C)) & I2C_SR2_MSL); // wait until bus released (non master mode)
-	return to_return;
+	const uint8_t address[] = {0x08+start}; // memory address for data
+	return i2c_read(RTC_DS1307_I2C_ADDR, address, LENGTH(address), data, LENGTH(data)); // read RAM (starting at 0x08)
 }
 
 bool rtc_ds1307_oscillator_disable(void)
 {
 	uint8_t data[1] = {0}; // to write CH value data over I2C
-	rtc_ds1307_read_memory(0, data, LENGTH(data)); // read seconds with CH value
+	const uint8_t address[] = {0x00}; // memory address for data
+	if (!i2c_read(RTC_DS1307_I2C_ADDR, address, LENGTH(address), data, LENGTH(data))) { // read seconds with CH value
+		return false;
+	}
 	data[0] |= 0x80; // set CH to disable oscillator
-	return rtc_ds1307_write_memory(0, data, LENGTH(data)); // write current seconds with CH value
+	return i2c_write(RTC_DS1307_I2C_ADDR, address, LENGTH(address), data, LENGTH(data)); // write current seconds with CH value
 }
 
 bool rtc_ds1307_oscillator_enable(void)
 {
 	uint8_t data[1] = {0}; // to write CH value data over I2C
-	rtc_ds1307_read_memory(0, data, LENGTH(data)); // read seconds with CH value
+	const uint8_t address[] = {0x00}; // memory address for data
+	if (!i2c_read(RTC_DS1307_I2C_ADDR, address, LENGTH(address), data, LENGTH(data))) { // read seconds with CH value
+		return false;
+	}
 	data[0] &= 0x7f; // clear CH to enable oscillator
-	return rtc_ds1307_write_memory(0, data, LENGTH(data)); // write current seconds with CH value
+	return i2c_write(RTC_DS1307_I2C_ADDR, address, LENGTH(address), data, LENGTH(data)); // write current seconds with CH value
 }
 
 bool rtc_ds1307_write_square_wave(uint16_t frequency)
@@ -310,7 +224,8 @@ bool rtc_ds1307_write_square_wave(uint16_t frequency)
 		default: // unspecified frequency
 			return false;
 	}
-	return rtc_ds1307_write_memory(7, data, LENGTH(data)); // write current seconds with CH value
+	const uint8_t address[] = {0x07}; // memory address for data
+	return i2c_write(RTC_DS1307_I2C_ADDR, address, LENGTH(address), data, LENGTH(data)); // write current seconds with CH value
 }
 
 bool rtc_ds1307_write_seconds(uint8_t seconds)
@@ -319,12 +234,14 @@ bool rtc_ds1307_write_seconds(uint8_t seconds)
 		return false;
 	}
 	uint8_t data[1] = {0}; // to read CH value data and write seconds value over I2C
-	if (!rtc_ds1307_read_memory(0, data, LENGTH(data))) { // read seconds with CH value
+	const uint8_t address[] = {0x00}; // memory address for data
+	if (!i2c_read(RTC_DS1307_I2C_ADDR, address, LENGTH(address), data, LENGTH(data))) { // read seconds with CH value
 		return false;
 	}
 	data[0] &= 0x80; // only keep CH flag
 	data[0] |= (((seconds/10)%6)<<4)+(seconds%10); // encode seconds in BCD format
-	return rtc_ds1307_write_memory(0, data, LENGTH(data)); // write current seconds with previous CH value
+
+	return i2c_write(RTC_DS1307_I2C_ADDR, address, LENGTH(address), data, LENGTH(data)); // write current seconds with previous CH value
 }
 
 bool rtc_ds1307_write_minutes(uint8_t minutes)
@@ -334,7 +251,9 @@ bool rtc_ds1307_write_minutes(uint8_t minutes)
 	}
 	uint8_t data[1] = {0}; // to write time value
 	data[0] = (((minutes/10)%6)<<4)+(minutes%10); // encode minutes in BCD format
-	return rtc_ds1307_write_memory(1, data, LENGTH(data)); // write time value on RTC
+
+	const uint8_t address[] = {0x01}; // memory address for data
+	return i2c_write(RTC_DS1307_I2C_ADDR, address, LENGTH(address), data, LENGTH(data)); // write time value on RTC
 }
 
 bool rtc_ds1307_write_hours(uint8_t hours)
@@ -344,7 +263,9 @@ bool rtc_ds1307_write_hours(uint8_t hours)
 	}
 	uint8_t data[1] = {0}; // to write time value
 	data[0] = (((hours/10)%3)<<4)+(hours%10); // encode hours in BCD 24h format
-	return rtc_ds1307_write_memory(2, data, LENGTH(data)); // write time value on RTC
+
+	const uint8_t address[] = {0x02}; // memory address for data
+	return i2c_write(RTC_DS1307_I2C_ADDR, address, LENGTH(address), data, LENGTH(data)); // write time value on RTC
 }
 
 bool rtc_ds1307_write_day(uint8_t day)
@@ -354,7 +275,9 @@ bool rtc_ds1307_write_day(uint8_t day)
 	}
 	uint8_t data[1] = {0}; // to write time value
 	data[0] = (day%8); // encode day in BCD format
-	return rtc_ds1307_write_memory(3, data, LENGTH(data)); // write time value on RTC
+
+	const uint8_t address[] = {0x03}; // memory address for data
+	return i2c_write(RTC_DS1307_I2C_ADDR, address, LENGTH(address), data, LENGTH(data)); // write time value on RTC
 }
 
 bool rtc_ds1307_write_date(uint8_t date)
@@ -364,7 +287,9 @@ bool rtc_ds1307_write_date(uint8_t date)
 	}
 	uint8_t data[1] = {0}; // to write time value
 	data[0] = (((date/10)%4)<<4)+(date%10); // encode date in BCD format
-	return rtc_ds1307_write_memory(4, data, LENGTH(data)); // write time value on RTC
+
+	const uint8_t address[] = {0x04}; // memory address for data
+	return i2c_write(RTC_DS1307_I2C_ADDR, address, LENGTH(address), data, LENGTH(data)); // write time value on RTC
 }
 
 bool rtc_ds1307_write_month(uint8_t month)
@@ -374,7 +299,9 @@ bool rtc_ds1307_write_month(uint8_t month)
 	}
 	uint8_t data[1] = {0}; // to write time value
 	data[0] = (((month/10)%2)<<4)+(month%10); // encode month in BCD format
-	return rtc_ds1307_write_memory(5, data, LENGTH(data)); // write time value on RTC
+
+	const uint8_t address[] = {0x05}; // memory address for data
+	return i2c_write(RTC_DS1307_I2C_ADDR, address, LENGTH(address), data, LENGTH(data)); // write time value on RTC
 }
 
 bool rtc_ds1307_write_year(uint8_t year)
@@ -384,17 +311,20 @@ bool rtc_ds1307_write_year(uint8_t year)
 	}
 	uint8_t data[1] = {0}; // to write time value
 	data[0] = (((year/10)%10)<<4)+(year%10); // encode year in BCD format
-	return rtc_ds1307_write_memory(6, data, LENGTH(data)); // write time value on RTC
+
+	const uint8_t address[] = {0x06}; // memory address for data
+	return i2c_write(RTC_DS1307_I2C_ADDR, address, LENGTH(address), data, LENGTH(data)); // write time value on RTC
 }
 
 bool rtc_ds1307_write_time(uint8_t seconds, uint8_t minutes, uint8_t hours, uint8_t day, uint8_t date, uint8_t month, uint8_t year)
 {
 	uint8_t data[7] = {0}; // to write all time values
+	const uint8_t address[] = {0x00}; // memory address for data
 	// seconds
 	if (seconds>59) {
 		return false;
 	}
-	if (!rtc_ds1307_read_memory(0, data, 1)) { // read seconds with CH value
+	if (!i2c_read(RTC_DS1307_I2C_ADDR, address, LENGTH(address), data, 1)) { // read seconds with CH value
 		return false;
 	}
 	data[0] &= 0x80; // only keep CH flag
@@ -430,7 +360,7 @@ bool rtc_ds1307_write_time(uint8_t seconds, uint8_t minutes, uint8_t hours, uint
 	}
 	data[6] = (((year/10)%10)<<4)+(year%10); // encode year in BCD format
 
-	return rtc_ds1307_write_memory(0, data, LENGTH(data)); // write time values on RTC
+	return i2c_write(RTC_DS1307_I2C_ADDR, address, LENGTH(address), data, LENGTH(data)); // write time value on RTC
 }
 
 bool rtc_ds1307_write_ram(uint8_t* data, uint8_t start, uint8_t length)
@@ -442,5 +372,6 @@ bool rtc_ds1307_write_ram(uint8_t* data, uint8_t start, uint8_t length)
 	if (start>55 || start+length>56) { // out of bounds RAM
 		return false;
 	}
-	return rtc_ds1307_write_memory(0x08+start, data, length); // write RAM (starting at 0x08)
+	const uint8_t address[] = {0x08+start}; // memory address for data
+	return i2c_write(RTC_DS1307_I2C_ADDR, address, LENGTH(address), data, LENGTH(data)); // write RAM (starting at 0x08)
 }