diff --git a/lib/onewire_master.c b/lib/onewire_master.c
index c9c9c03..56ad126 100644
--- a/lib/onewire_master.c
+++ b/lib/onewire_master.c
@@ -17,13 +17,14 @@
  *  @author King Kévin <kingkevin@cuvoodoo.info>
  *  @date 2017
  *  @note peripherals used: timer @ref onewire_master_timer, GPIO @ref onewire_master_gpio
- *  @warning this library does not support parasite power mode
+ *  @note overdrive mode is not supported
+ *  @warning this library does not support active parasite power mode (more than the pull-up resistor itself)
  */
 
 /* standard libraries */
 #include <stdint.h> // standard integer types
 #include <stdbool.h> // boolean type
-#include <stdlib.h> // memory utilities
+#include <stddef.h> // NULL definition
 
 /* STM32 (including CM3) libraries */
 #include <libopencmsis/core_cm3.h> // Cortex M3 utilities
@@ -64,8 +65,8 @@ volatile enum {
 
 volatile bool slave_presence = false; /**< if slaves have been detected */
 uint8_t* buffer = NULL; /**< input/output buffer for read/write commands/functions */
-size_t buffer_size = 0; /**< size of buffer in bits */
-volatile size_t buffer_bit = 0; /**< number of bits read/written */
+uint32_t buffer_size = 0; /**< size of buffer in bits */
+volatile uint32_t buffer_bit = 0; /**< number of bits read/written */
 
 void onewire_master_setup(void)
 {
@@ -81,10 +82,10 @@ void onewire_master_setup(void)
 	timer_set_prescaler(TIM(ONEWIRE_MASTER_TIMER), 1-1); // don't use prescale since this 16 bits timer allows to wait > 480 us used for the reset pulse ( 1/(72E6/1/(2**16))=910us )
 
 	// use comparator to time signal (without using the output), starting at slot start
-	timer_set_oc_value(TIM(ONEWIRE_MASTER_TIMER), TIM_OC1, 1*(rcc_ahb_frequency/1000000)); // use compare function to time master pulling low (1 < Tlowr < 15)
-	timer_set_oc_value(TIM(ONEWIRE_MASTER_TIMER), TIM_OC2, 7*(rcc_ahb_frequency/1000000)); // use compare function to read of write (1 < Trw < 15)
-	timer_set_oc_value(TIM(ONEWIRE_MASTER_TIMER), TIM_OC3, 62*(rcc_ahb_frequency/1000000)); // use compare function to end time slot (60 < Tslot < 120), this will be followed by a recovery time (end of timer)
-	timer_set_oc_value(TIM(ONEWIRE_MASTER_TIMER), TIM_OC4, 120*(rcc_ahb_frequency/1000000)); // use compare function to detect slave presence (60 < Tpdl < 240)
+	timer_set_oc_value(TIM(ONEWIRE_MASTER_TIMER), TIM_OC1, 1*(rcc_ahb_frequency/1000000)-1); // use compare function to time master pulling low (1 < Tlowr < 15)
+	timer_set_oc_value(TIM(ONEWIRE_MASTER_TIMER), TIM_OC2, 7*(rcc_ahb_frequency/1000000)-1); // use compare function to read of write (1 < Trw < 15)
+	timer_set_oc_value(TIM(ONEWIRE_MASTER_TIMER), TIM_OC3, 62*(rcc_ahb_frequency/1000000)-1); // use compare function to end time slot (60 < Tslot < 120), this will be followed by a recovery time (end of timer)
+	timer_set_oc_value(TIM(ONEWIRE_MASTER_TIMER), TIM_OC4, 120*(rcc_ahb_frequency/1000000)-1); // use compare function to detect slave presence (60 < Tpdl < 240)
 	
 	timer_clear_flag(TIM(ONEWIRE_MASTER_TIMER), TIM_SR_UIF); // clear update (overflow) flag
 	timer_update_on_overflow(TIM(ONEWIRE_MASTER_TIMER)); // only use counter overflow as UEV source (use overflow as start time or timeout)
@@ -100,7 +101,7 @@ bool onewire_master_reset(void)
 	// prepare timer
 	timer_disable_counter(TIM(ONEWIRE_MASTER_TIMER)); // disable timer to reconfigure it
 	timer_set_counter(TIM(ONEWIRE_MASTER_TIMER),0); // reset counter
-	timer_set_period(TIM(ONEWIRE_MASTER_TIMER), 490*(rcc_ahb_frequency/1000000)); // set timeout to > 480 us (490)
+	timer_set_period(TIM(ONEWIRE_MASTER_TIMER), 490*(rcc_ahb_frequency/1000000)-1); // set timeout to > 480 us
 
 	slave_presence = false; // reset state
 	onewire_master_state = ONEWIRE_STATE_MASTER_RESET; // set new state
@@ -119,7 +120,7 @@ bool onewire_master_reset(void)
 }
 
 /** write bits on 1-Wire bus
- *  @warning buffer_size must be set to the number of bits to write and buffer must contain the data to write
+ *  @warning buffer_size must be set to the number of bits to writen and buffer must contain the data to write
  *  @return if write succeeded
  */
 static bool onewire_master_write(void)
@@ -139,7 +140,7 @@ static bool onewire_master_write(void)
 	// start writing
 	gpio_clear(GPIO(ONEWIRE_MASTER_PORT),GPIO(ONEWIRE_MASTER_PIN)); // pull signal low to start slot
 	timer_enable_counter(TIM(ONEWIRE_MASTER_TIMER)); // start timer
-	while (onewire_master_state!=ONEWIRE_STATE_DONE && onewire_master_state!=ONEWIRE_STATE_ERROR) { // wait until reset procedure completed
+	while (onewire_master_state!=ONEWIRE_STATE_DONE && onewire_master_state!=ONEWIRE_STATE_ERROR) { // wait until write procedure completed
 		__WFI(); // go to sleep
 	}
 	if (ONEWIRE_STATE_ERROR==onewire_master_state) { // an error occurred
@@ -157,9 +158,6 @@ static bool onewire_master_read(void)
 	if (0==buffer_size) { // check input
 		return false;
 	}
-	if (!(buffer=realloc(buffer, (buffer_size-1)/8+1))) { // allocate memory
-		return false; // error in memory allocation
-	}
 	buffer_bit = 0; // reset bit index
 	onewire_master_state = ONEWIRE_STATE_MASTER_READ; // set new state
 
@@ -175,7 +173,7 @@ static bool onewire_master_read(void)
 	// start reading
 	gpio_clear(GPIO(ONEWIRE_MASTER_PORT),GPIO(ONEWIRE_MASTER_PIN)); // pull signal low to start slot
 	timer_enable_counter(TIM(ONEWIRE_MASTER_TIMER)); // start timer
-	while (onewire_master_state!=ONEWIRE_STATE_DONE && onewire_master_state!=ONEWIRE_STATE_ERROR) { // wait until reset procedure completed
+	while (onewire_master_state!=ONEWIRE_STATE_DONE && onewire_master_state!=ONEWIRE_STATE_ERROR) { // wait until read procedure completed
 		__WFI(); // go to sleep
 	}
 	if (ONEWIRE_STATE_ERROR==onewire_master_state) { // an error occurred
@@ -184,14 +182,14 @@ static bool onewire_master_read(void)
 	return true;
 }
 
-uint8_t onewire_master_crc(uint8_t* data, size_t size)
+uint8_t onewire_master_crc(uint8_t* data, uint32_t length)
 {
-	if (NULL==data || 0==size) { // check input
+	if (NULL==data || 0==length) { // check input
 		return 0; // wrong input
 	}
 	
 	uint8_t crc = 0x00; // initial value
-	for (uint8_t i=0; i<size; i++) { // go through every byte
+	for (uint8_t i=0; i<length; i++) { // go through every byte
 		crc ^= data[i]; // XOR byte
 		for (uint8_t b=0; b<8; b++) { // go through every bit
 			if (crc&0x01) { // least significant bit is set (we are using the reverse way)
@@ -204,14 +202,11 @@ uint8_t onewire_master_crc(uint8_t* data, size_t size)
 	return crc;
 }
 
-bool onewire_master_function_read(uint8_t function, uint8_t* data, size_t bits)
+bool onewire_master_function_read(uint8_t function, uint8_t* data, uint32_t bits)
 {
 	// send function command
 	buffer_size = 8; // function command is only one byte
-	if (!(buffer=realloc(buffer, (buffer_size-1)/8+1))) { // allocate memory
-		return false; // error in memory allocation
-	}
-	buffer[0] = function; // set function command
+	buffer = &function; // set the buffer to the function code
 	if (!onewire_master_write()) { // send command
 		return false; // an error occurred
 	}
@@ -222,52 +217,19 @@ bool onewire_master_function_read(uint8_t function, uint8_t* data, size_t bits)
 
 	// read data
 	buffer_size = bits; // save number of bits to read
+	buffer = data; // set the buffer to the data to write
 	if (!onewire_master_read()) { // read bits from slave
 		return false; // an error occurred
 	}
 
-	// copy data to user buffer
-	for (uint8_t i=0; i<bits/8; i++) { // copy bytes
-		data[i] = buffer[i]; // copy data
-	}
-	// copy remaining bits
-	switch (bits%8) {
-		case 1:
-			data[(bits-1)/8] = data[(bits-1)/8]&0x01;
-			break;
-		case 2:
-			data[(bits-1)/8] = data[(bits-1)/8]&0x03;
-			break;
-		case 3:
-			data[(bits-1)/8] = data[(bits-1)/8]&0x07;
-			break;
-		case 4:
-			data[(bits-1)/8] = data[(bits-1)/8]&0x0f;
-			break;
-		case 5:
-			data[(bits-1)/8] = data[(bits-1)/8]&0x1f;
-			break;
-		case 6:
-			data[(bits-1)/8] = data[(bits-1)/8]&0x3f;
-			break;
-		case 7:
-			data[(bits-1)/8] = data[(bits-1)/8]&0x7f;
-			break;
-		case 0: // no bits remaining
-			break;
-	}
-	
 	return true;
 }
 
-bool onewire_master_function_write(uint8_t function, uint8_t* data, size_t bits)
+bool onewire_master_function_write(uint8_t function, uint8_t* data, uint32_t bits)
 {
 	// send function command
 	buffer_size = 8; // function command is only one byte
-	if (!(buffer=realloc(buffer, (buffer_size-1)/8+1))) { // allocate memory
-		return false; // error in memory allocation
-	}
-	buffer[0] = function; // set function command
+	buffer = &function; // set the buffer to the function code
 	if (!onewire_master_write()) { // send command
 		return false; // an error occurred
 	}
@@ -278,12 +240,7 @@ bool onewire_master_function_write(uint8_t function, uint8_t* data, size_t bits)
 
 	// copy data from user buffer
 	buffer_size = bits; // save number of bits to write
-	if (!(buffer=realloc(buffer, (buffer_size-1)/8+1))) { // allocate memory
-		return false; // error in memory allocation
-	}
-	for (uint8_t i=0; i<(buffer_size-1)/8+1; i++) { // copy bytes
-		buffer[i] = data[i]; // copy data
-	}
+	buffer = data; // set the buffer to the data to write
 	// write data
 	if (!onewire_master_write()) { // read bits from slave
 		return false; // an error occurred
@@ -304,7 +261,7 @@ uint64_t onewire_master_rom_read(void)
 	
 	// return ROM code
 	uint64_t code = 0;
-	for (size_t i=0; i<8; i++) {
+	for (uint32_t i=0; i<8; i++) {
 		code += (uint64_t)rom_code[i]<<(8*i); // add byte
 	}
 	
@@ -329,6 +286,7 @@ bool onewire_master_rom_search(uint64_t* code, bool alarm)
 		*code = 0; // restart search codes
 	}
 
+	buffer = (uint8_t*){0}; // buffer to read up to two bits
 	for (uint8_t bit=0; bit<64; bit++) { // go through all 64 bits ROM code
 		buffer_size = 2; // read two first bits to detect conflict
 		if (!onewire_master_read()) { // read ROM ID from slave
@@ -353,9 +311,6 @@ bool onewire_master_rom_search(uint64_t* code, bool alarm)
 				goto end; // an error has occurred
 		}
 		buffer_size = 1; // to send next bit
-		if (!(buffer=realloc(buffer, 1))) { // allocate memory
-			goto end; // an error has occurred
-		}
 		buffer[0] = (*code>>bit); // set bit to send
 		if (!onewire_master_write()) { // send bit
 			goto end; // an error has occurred
diff --git a/lib/onewire_master.h b/lib/onewire_master.h
index f5edba5..6b60b6c 100644
--- a/lib/onewire_master.h
+++ b/lib/onewire_master.h
@@ -17,7 +17,8 @@
  *  @author King Kévin <kingkevin@cuvoodoo.info>
  *  @date 2017
  *  @note peripherals used: timer @ref onewire_master_timer, GPIO @ref onewire_master_gpio
- *  @warning this library does not support parasite power mode
+ *  @note overdrive mode is not supported
+ *  @warning this library does not support active parasite power mode (more than the pull-up resistor itself)
  */
 #pragma once
 
@@ -30,11 +31,11 @@ bool onewire_master_reset(void);
 /** compute CRC for 1-Wire
  *  @note this CRC-8 uses normal polynomial 0x31, reverse polynomial 0x8C, start value 0x00
  *  @param[in] data bytes on which to calculate CRC checksum on
- *  @param[in] size number of bytes in data
+ *  @param[in] length number of bytes in data
  *  @return computed CRC checksum
  */
-uint8_t onewire_master_crc(uint8_t* data, size_t size);
-/** send READ ROM command
+uint8_t onewire_master_crc(uint8_t* data, uint32_t length);
+/** send READ ROM command and read ROM code response
  *  @note user needs to send reset pulse before
  *  @return ROM code read
  */
@@ -65,7 +66,7 @@ bool onewire_master_rom_match(uint64_t code);
  *  @param[in] bits number of bits to read (0 if only the function command should be sent)
  *  @return if operation succeeded
  */
-bool onewire_master_function_read(uint8_t function, uint8_t* data, size_t bits);
+bool onewire_master_function_read(uint8_t function, uint8_t* data, uint32_t bits);
 /** issue function and write data
  *  @note user needs to send a ROM command before
  *  @param[in] function function command to send
@@ -73,4 +74,4 @@ bool onewire_master_function_read(uint8_t function, uint8_t* data, size_t bits);
  *  @param[in] bits number of bits to write (0 if only the function command should be sent)
  *  @return if operation succeeded
  */
-bool onewire_master_function_write(uint8_t function, uint8_t* data, size_t bits);
+bool onewire_master_function_write(uint8_t function, uint8_t* data, uint32_t bits);