diff --git a/lib/led_tm1637.c b/lib/led_tm1637.c
new file mode 100644
index 0000000..2d11b11
--- /dev/null
+++ b/lib/led_tm1637.c
@@ -0,0 +1,327 @@
+/* This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see .
+ *
+ */
+/** library to communicate with a Titan Micro TM1637 IC attached to a 4-digit 7-segment (code)
+ * @file led_tm1637.c
+ * @author King Kévin
+ * @date 2017
+ * @note peripherals used: GPIO @ref led_tm1637_gpio, timer @ref led_tm1637_timer
+ * @note the protocol is very similar to I2C but incompatible for the following reasons: the capacitance is too large for open-drain type output with weak pull-up resistors (push-pull needs to be used, preventing to get ACKs since no indication of the ACK timing is provided); the devices doesn't use addresses; the STM32 I2C will switch to receiver mode when the first sent byte (the I2C address) has last bit set to 1 (such as for address commands with B7=1 where B7 is transmitted last), preventing to send further bytes (the data byte after the address)
+ * @warning all calls are blocking
+ *
+ * bit vs segment: 0bpgfedcba
+ * +a+
+ * f b p
+ * +g+
+ * e c p
+ * +d+
+ */
+
+/* standard libraries */
+#include // standard integer types
+#include // general utilities
+#include // string utilities
+
+/* STM32 (including CM3) libraries */
+#include // Cortex M3 utilities
+#include // real-time control clock library
+#include // general purpose input output library
+#include // timer library
+
+#include "global.h" // global utilities
+#include "led_tm1637.h" // TM1637 header and definitions
+
+/** @defgroup led_tm1637_gpio GPIO used to communication with TM1637 IC
+ * @{
+ */
+#define LED_TM1637_CLK_PORT B /**< port for CLK signal */
+#define LED_TM1637_CLK_PIN 6 /**< pin for CLK signal */
+#define LED_TM1637_DIO_PORT B /**< port for DIO signal */
+#define LED_TM1637_DIO_PIN 7 /**< pin for DIO signal */
+/** @} */
+
+/** @defgroup led_tm1637_timer timer used to communication with TM1637 IC
+ * @{
+ */
+#define LED_TM1637_TIMER 3 /**< timer to create signal */
+/** @} */
+
+/** display brightness */
+static enum led_tm1637_brightness_t display_brightness = LED_TM1637_14DIV16;
+/** if display is on */
+static bool display_on = false;
+
+/** ASCII characters encoded for the 7 segments digit block
+ * @note starts with space
+ */
+static const uint8_t ascii_7segments[] = {
+ 0x00, // 0b00000000 space
+ 0x30, // 0b00110000 ! (I)
+ 0x22, // 0b00100010 "
+ 0x5c, // 0b01011100 # (o)
+ 0x6d, // 0b01101101 $ (s)
+ 0x52, // 0b01010010 % (/)
+ 0x7d, // 0b01111101 & (6)
+ 0x20, // 0b00100000 '
+ 0x39, // 0b00111001 ( ([)
+ 0x0f, // 0b00001111 )
+ 0x70, // 0b01110000 *
+ 0x46, // 0b01000110 +
+ 0x10, // 0b00010000 ,
+ 0x40, // 0b01000000 -
+ 0x10, // 0b00010000 . (,)
+ 0x52, // 0b01010010 /
+ 0x3f, // 0b00111111 0
+ 0x06, // 0b00000110 1
+ 0x5b, // 0b01011011 2
+ 0x4f, // 0b01001111 3
+ 0x66, // 0b01100110 4
+ 0x6d, // 0b01101101 5
+ 0x7d, // 0b01111101 6
+ 0x07, // 0b00000111 7
+ 0x7f, // 0b01111111 8
+ 0x6f, // 0b01101111 9
+ 0x48, // 0b01001000 : (=)
+ 0x48, // 0b01001000 ; (=)
+ 0x58, // 0b01011000 <
+ 0x48, // 0b01001000 =
+ 0x4c, // 0b01001100 >
+ 0x53, // 0b01010011 ?
+ 0x7b, // 0b01111011 @
+ 0x77, // 0b01110111 A
+ 0x7f, // 0b01111111 B
+ 0x39, // 0b00111001 C
+ 0x5e, // 0b01011110 D
+ 0x79, // 0b01111001 E
+ 0x71, // 0b01110001 F
+ 0x3d, // 0b00111101 G
+ 0x76, // 0b01110110 H
+ 0x30, // 0b00110000 I
+ 0x1e, // 0b00011110 J
+ 0x76, // 0b01110110 K
+ 0x38, // 0b00111000 L
+ 0x37, // 0b00110111 M
+ 0x37, // 0b00110111 N
+ 0x3f, // 0b00111111 O
+ 0x73, // 0b01110011 P
+ 0x6b, // 0b01101011 Q
+ 0x33, // 0b00110011 R
+ 0x6d, // 0b01101101 S
+ 0x78, // 0b01111000 T
+ 0x3e, // 0b00111110 U
+ 0x3e, // 0b00111110 V (U)
+ 0x3e, // 0b00111110 W (U)
+ 0x76, // 0b01110110 X (H)
+ 0x6e, // 0b01101110 Y
+ 0x5b, // 0b01011011 Z
+ 0x39, // 0b00111001 [
+ 0x64, // 0b01100100 '\'
+ 0x0f, // 0b00001111 /
+ 0x23, // 0b00100011 ^
+ 0x08, // 0b00001000 _
+ 0x02, // 0b00000010 `
+ 0x5f, // 0b01011111 a
+ 0x7c, // 0b01111100 b
+ 0x58, // 0b01011000 c
+ 0x5e, // 0b01011110 d
+ 0x7b, // 0b01111011 e
+ 0x71, // 0b01110001 f
+ 0x6f, // 0b01101111 g
+ 0x74, // 0b01110100 h
+ 0x10, // 0b00010000 i
+ 0x0c, // 0b00001100 j
+ 0x76, // 0b01110110 k
+ 0x30, // 0b00110000 l
+ 0x54, // 0b01010100 m
+ 0x54, // 0b01010100 n
+ 0x5c, // 0b01011100 o
+ 0x73, // 0b01110011 p
+ 0x67, // 0b01100111 q
+ 0x50, // 0b01010000 r
+ 0x6d, // 0b01101101 s
+ 0x78, // 0b01111000 t
+ 0x1c, // 0b00011100 u
+ 0x1c, // 0b00011100 v (u)
+ 0x1c, // 0b00011100 w (u)
+ 0x76, // 0b01110110 x
+ 0x6e, // 0b01101110 y
+ 0x5b, // 0b01011011 z
+ 0x39, // 0b00111001 { ([)
+ 0x30, // 0b00110000 |
+ 0x0f, // 0b00001111 } ([)
+ 0x40, // 0b01000000 ~
+};
+
+void led_tm1637_setup(void)
+{
+ // configure GPIO for CLK and DIO signals
+ rcc_periph_clock_enable(RCC_GPIO(LED_TM1637_CLK_PORT)); // enable clock for GPIO peripheral
+ gpio_set(GPIO(LED_TM1637_CLK_PORT), GPIO(LED_TM1637_CLK_PIN)); // idle high
+ gpio_set_mode(GPIO(LED_TM1637_CLK_PORT), GPIO_MODE_OUTPUT_10_MHZ, GPIO_CNF_OUTPUT_PUSHPULL, GPIO(LED_TM1637_CLK_PIN)); // master start the communication (capacitance is to large for open drain), only switch to input for ack from slave
+ rcc_periph_clock_enable(RCC_GPIO(LED_TM1637_DIO_PORT)); // enable clock for GPIO peripheral
+ gpio_set(GPIO(LED_TM1637_DIO_PORT), GPIO(LED_TM1637_DIO_PIN)); // idle high
+ gpio_set_mode(GPIO(LED_TM1637_DIO_PORT), GPIO_MODE_OUTPUT_10_MHZ, GPIO_CNF_OUTPUT_PUSHPULL, GPIO(LED_TM1637_DIO_PIN)); // master start the communication (capacitance is to large for open drain), only switch to input for ack from slave
+ // first clock then data high also stands for stop condition
+
+ // setup timer to create signal timing (each tick is used for a single GPIO transition)
+ rcc_periph_clock_enable(RCC_TIM(LED_TM1637_TIMER)); // enable clock for timer block
+ timer_reset(TIM(LED_TM1637_TIMER)); // reset timer state
+ timer_set_mode(TIM(LED_TM1637_TIMER), TIM_CR1_CKD_CK_INT, TIM_CR1_CMS_EDGE, TIM_CR1_DIR_UP); // set timer mode, use undivided timer clock, edge alignment (simple count), and count up
+ timer_set_prescaler(TIM(LED_TM1637_TIMER), 0); // don't prescale to get most precise timing ( 1/(72E6/1/(2**16))=0.91 ms > 0.5 us )
+ timer_set_period(TIM(LED_TM1637_TIMER), 500); // set the clock frequency (emprical value until the signal starts to look bad)
+ timer_clear_flag(TIM(LED_TM1637_TIMER), TIM_SR_UIF); // clear flag
+ timer_update_on_overflow(TIM(LED_TM1637_TIMER)); // only use counter overflow as UEV source (use overflow as start time or timeout)
+}
+
+/** wait until clock tick (timer overflow) occurred
+ */
+static inline void led_tm1637_tick(void)
+{
+ while (!timer_get_flag(TIM(LED_TM1637_TIMER), TIM_SR_UIF)); // wait until counter overflow update event happens
+ timer_clear_flag(TIM(LED_TM1637_TIMER), TIM_SR_UIF); // clear event flag
+}
+
+/** write data on bus
+ * @param[in] data bytes to write
+ * @param[in] length number of bytes to write
+ * @return if write succeeded
+ * @note includes start and stop conditions
+ */
+static bool led_tm1637_write(const uint8_t* data, size_t length)
+{
+ bool to_return = true; // return if write succeeded
+ if (data==NULL || length==0) { // verify there it data to be read
+ return false;
+ }
+
+ // enable timer for signal generation
+ timer_set_counter(TIM(LED_TM1637_TIMER), 0); // reset timer counter
+ timer_enable_counter(TIM(LED_TM1637_TIMER)); // enable timer to generate timing
+ led_tm1637_tick(); // wait to enforce minimum time since last write
+
+ // send start condition (DIO then CLK low)
+ gpio_clear(GPIO(LED_TM1637_DIO_PORT), GPIO(LED_TM1637_DIO_PIN)); // put DIO low
+ led_tm1637_tick(); // wait for next tick
+ gpio_clear(GPIO(LED_TM1637_CLK_PORT), GPIO(LED_TM1637_CLK_PIN)); // put CLK low
+
+ // send data bytes (MSb first)
+ for (size_t i=0; i>= 1; // shift data
+ led_tm1637_tick(); // wait for next tick
+ gpio_set(GPIO(LED_TM1637_CLK_PORT), GPIO(LED_TM1637_CLK_PIN)); // put CLK high
+ led_tm1637_tick(); // wait for next tick (no DIO transition when CLK is high)
+ gpio_clear(GPIO(LED_TM1637_CLK_PORT), GPIO(LED_TM1637_CLK_PIN)); // put CLK low
+ }
+ gpio_set_mode(GPIO(LED_TM1637_DIO_PORT), GPIO_MODE_INPUT, GPIO_CNF_INPUT_FLOAT, GPIO(LED_TM1637_DIO_PIN)); // switch DIO as input to read ACK
+ led_tm1637_tick(); // wait for next tick (when the slave should ACK)
+ gpio_set(GPIO(LED_TM1637_CLK_PORT), GPIO(LED_TM1637_CLK_PIN)); // put CLK high
+ if (gpio_get(GPIO(LED_TM1637_DIO_PORT), GPIO(LED_TM1637_DIO_PIN))) { // no ACK received
+ to_return = false; // remember there was an error
+ break; // stop sending bytes
+ }
+ led_tm1637_tick(); // wait for next tick
+ gpio_clear(GPIO(LED_TM1637_CLK_PORT), GPIO(LED_TM1637_CLK_PIN)); // put CLK low
+ gpio_set_mode(GPIO(LED_TM1637_DIO_PORT), GPIO_MODE_OUTPUT_2_MHZ, GPIO_CNF_OUTPUT_PUSHPULL, GPIO(LED_TM1637_DIO_PIN)); // switch DIO back to output to send next byte
+ }
+
+ // send stop condition
+ gpio_set_mode(GPIO(LED_TM1637_DIO_PORT), GPIO_MODE_OUTPUT_2_MHZ, GPIO_CNF_OUTPUT_PUSHPULL, GPIO(LED_TM1637_DIO_PIN)); // ensure DIO is output (in case no ACK as been received
+ led_tm1637_tick(); // wait for next tick
+ gpio_set(GPIO(LED_TM1637_CLK_PORT), GPIO(LED_TM1637_CLK_PIN)); // put CLK high
+ led_tm1637_tick(); // wait for next tick
+ gpio_set(GPIO(LED_TM1637_DIO_PORT), GPIO(LED_TM1637_DIO_PIN)); // put DIO high
+ timer_disable_counter(TIM(LED_TM1637_TIMER)); // stop timer since it's not used anymore
+
+ return to_return;
+}
+
+bool led_tm1637_on(void)
+{
+ uint8_t data[] = { 0x88+display_brightness }; // command to turn display on (use set brightness)
+ bool to_return = false; // result to return
+ if (led_tm1637_write(data,LENGTH(data))) { // send command
+ display_on = true; // remember display is on
+ to_return = true; // command succeeded
+ }
+ return to_return; // return result
+}
+
+bool led_tm1637_off(void)
+{
+ uint8_t data[] = { 0x80+display_brightness }; // command to turn display off (use set brightness)
+ if (led_tm1637_write(data,LENGTH(data))) { // send command
+ display_on = false; // remember display is off
+ return true; // command succeeded
+ }
+ return false; // return result
+}
+
+bool led_tm1637_brightness(enum led_tm1637_brightness_t brightness)
+{
+ display_brightness = brightness; // save brightness
+ if (display_on) { // adjust brightness if display is on
+ return led_tm1637_on(); // adjust brightness
+ } else {
+ return true; // command succeeded
+ }
+ return false;
+}
+
+bool led_tm1637_number(uint16_t number)
+{
+ uint8_t write_data[] = { 0x40 }; // command: write data, automatic address adding, normal
+ uint8_t data[] = { 0xc0, ascii_7segments[((number/1000)%10)+'0'-' '], ascii_7segments[((number/100)%10)+'0'-' '], ascii_7segments[((number/10)%10)+'0'-' '], ascii_7segments[((number/1)%10)+'0'-' '] }; // set address C0H and add data
+
+ if (led_tm1637_write(write_data,LENGTH(write_data)) && led_tm1637_write(data,LENGTH(data))) { // send commands
+ return true;
+ }
+ return false;
+}
+
+bool led_tm1637_time(uint8_t hours, uint8_t minutes)
+{
+ uint8_t write_data[] = { 0x40 }; // command: write data, automatic address adding, normal
+ uint8_t data[] = { 0xc0, ascii_7segments[((hours/10)%10)+'0'-' '], ascii_7segments[((hours/1)%10)+'0'-' ']|0x80, ascii_7segments[((minutes/10)%10)+'0'-' '], ascii_7segments[((minutes/1)%10)+'0'-' '] }; // set address C0H and add data
+
+ if (led_tm1637_write(write_data,LENGTH(write_data)) && led_tm1637_write(data,LENGTH(data))) { // send commands
+ return true;
+ }
+ return false;
+}
+
+bool led_tm1637_text(char* text)
+{
+ if (strlen(text)!=4) { // input text should have exactly 4 characters
+ return false;
+ }
+ for (uint8_t i=0; i<4; i++) { // input text should only contain printable character (8th bit is used for dots)
+ if ((text[i]&0x7f)<' ' || (text[i]&0x7f)>=' '+LENGTH(ascii_7segments)) {
+ return false;
+ }
+ }
+ uint8_t write_data[] = { 0x40 }; // command: write data, automatic address adding, normal
+ uint8_t data[] = { 0xc0, ascii_7segments[(text[0]&0x7f)-' ']|(text[0]&0x80), ascii_7segments[(text[1]&0x7f)-' ']|(text[1]&0x80), ascii_7segments[(text[2]&0x7f)-' ']|(text[2]&0x80), ascii_7segments[(text[3]&0x7f)-' ']|(text[3]&0x80) }; // set address C0H and add data
+
+ if (led_tm1637_write(write_data,LENGTH(write_data)) && led_tm1637_write(data,LENGTH(data))) { // send commands
+ return true;
+ }
+ return false;
+}
diff --git a/lib/led_tm1637.h b/lib/led_tm1637.h
new file mode 100644
index 0000000..7bd0109
--- /dev/null
+++ b/lib/led_tm1637.h
@@ -0,0 +1,71 @@
+/* This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see .
+ *
+ */
+/** library to communicate with a Titan Micro TM1637 IC attached to a 4-digit 7-segment (API)
+ * @file led_tm1637.h
+ * @author King Kévin
+ * @date 2017
+ * @note peripherals used: GPIO @ref led_tm1637_gpio, timer @ref led_tm1637_timer
+ * @warning all calls are blocking
+ */
+#pragma once
+
+/** display brightness levels
+ */
+enum led_tm1637_brightness_t {
+ LED_TM1637_1DIV16 = 0,
+ LED_TM1637_2DIV16 = 1,
+ LED_TM1637_4DIV16 = 2,
+ LED_TM1637_10DIV16 = 3,
+ LED_TM1637_11DIV16 = 4,
+ LED_TM1637_12DIV16 = 5,
+ LED_TM1637_13DIV16 = 6,
+ LED_TM1637_14DIV16 = 7,
+};
+
+/** setup communication with TM1637 IC
+ */
+void led_tm1637_setup(void);
+/** switch display on
+ * @return if transmission succeeded
+ */
+bool led_tm1637_on(void);
+/** switch display off
+ * @return if transmission succeeded
+ */
+bool led_tm1637_off(void);
+/** set display brightness
+ * @param[in] brightness brightness level to set
+ * @return if transmission succeeded
+ */
+bool led_tm1637_brightness(enum led_tm1637_brightness_t brightness);
+/** display number
+ * @param[in] number number to display (0-9999)
+ * @return if transmission succeeded
+ */
+bool led_tm1637_number(uint16_t number);
+/** display time
+ * @param[in] hours hours to display (0-99)
+ * @param[in] minutes minutes to display (0-99)
+ * @note display separator between hours and minutes
+ * @return if transmission succeeded
+ */
+bool led_tm1637_time(uint8_t hours, uint8_t minutes);
+/** display text
+ * @param[in] text text to display (4 characters)
+ * @note use first bit of each character to enable dot
+ * @return if transmission succeeded
+ */
+bool led_tm1637_text(char* text);
+