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RIOT/drivers/tm1637/tm1637.c

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/*
* Copyright (C) 2024 Nico Behrens <nifrabe@outlook.de>
*
* This file is subject to the terms and conditions of the GNU Lesser
* General Public License v2.1. See the file LICENSE in the top level
* directory for more details.
*/
/**
* @ingroup drivers_tm1637
*
* @{
* @file
* @brief Driver for the TM1637 4-digit 7-segment display
*
* @author Nico Behrens <nifrabe@outlook.de>
*
* @}
*/
#include "tm1637.h"
#include "periph/gpio.h"
#include "ztimer.h"
#include "log.h"
/**
* @brief Amount of digits
*/
#define DIGIT_COUNT 4
/**
* @brief Signals data transmission
*/
#define COMMAND_DATA 0x40
/**
* @brief Sets the brightness and display state to on/off
*/
#define COMMAND_DISPLAY_AND_CONTROL 0x80
/**
* @brief Sets the address where data is written
*/
#define COMMAND_ADDRESS 0xC0
/**
* @brief Bit mask for turning the display on/off
*
* @note This bit is part of the COMMAND_DISPLAY_AND_CONTROL
*/
#define BIT_MASK_ON 0x08
/**
* @brief Bit mask for the dot/colon to the right of a digit
*
* @note This bit is part of a digit's segment data
*/
#define BIT_MASK_DOT 0x80
/**
* @brief Delay between bits in microseconds
*/
#define BIT_TIME_US 1
/**
* @brief Array encoding the segments for the digits from 0 to 9
*/
static const uint8_t segments_array[] = {
0b00111111, // 0
0b00000110, // 1
0b01011011, // 2
0b01001111, // 3
0b01100110, // 4
0b01101101, // 5
0b01111101, // 6
0b00000111, // 7
0b01111111, // 8
0b01101111, // 9
};
/**
* @brief Minus sign for negative numbers
*/
static const uint8_t minus_sign = 0b01000000;
/**
* @brief Delays the transmission to the display
*/
inline static void _tm1637_delay(void)
{
ztimer_sleep(ZTIMER_USEC, BIT_TIME_US);
}
/**
* @brief Starts the transmission to the display
*
* @param[in] dev device descriptor of the display
*/
static void _tm1637_start(const tm1637_t *dev)
{
gpio_write(dev->params->dio, false);
_tm1637_delay();
}
/**
* @brief Stops the transmission to the display
*
* @note A stop is needed after transmission of certain bytes according to
* the specification.
*
* @param[in] dev device descriptor of the display
*/
static void _tm1637_stop(const tm1637_t *dev)
{
gpio_write(dev->params->dio, false);
_tm1637_delay();
gpio_write(dev->params->clk, true);
_tm1637_delay();
gpio_write(dev->params->dio, true);
_tm1637_delay();
}
/**
* @brief Transmits a single byte to the display
*
* @param[in] dev device descriptor of the display
* @param[in] byte byte to transmit
*
* @retval 0 if the transmission was successful
* @retval -1 if the transmission failed
*/
static int _tm1637_transmit_byte(const tm1637_t *dev, uint8_t byte)
{
/* transmit each bit */
for (int i = 0; i < 8; ++i) {
bool value = (byte >> i) & 0x01;
gpio_write(dev->params->clk, false);
_tm1637_delay();
gpio_write(dev->params->dio, value);
_tm1637_delay();
gpio_write(dev->params->clk, true);
_tm1637_delay();
}
gpio_write(dev->params->clk, false);
gpio_write(dev->params->dio, true);
/* set the DIO pin to input to later receive the ACK */
gpio_init(dev->params->dio, GPIO_IN_PU);
_tm1637_delay();
gpio_write(dev->params->clk, true);
/* the transmission is successful if the GPIO reads LOW */
bool nack = gpio_read(dev->params->dio);
_tm1637_delay();
/* set the DIO pin back to output */
gpio_init(dev->params->dio, GPIO_OUT);
gpio_write(dev->params->dio, false);
gpio_write(dev->params->clk, false);
_tm1637_delay();
return nack ? -1 : 0;
}
/**
* @brief Transmits the segments array of length 4 to the display
*
* @param[in] dev device descriptor of the display
* @param[in] segments array of length 4 encoding the display's segments
*
* @retval 0 if the transmission was successful
* @retval -1 if the transmission failed
*/
static int _tm1637_transmit_segments(const tm1637_t *dev,
const uint8_t segments[DIGIT_COUNT],
tm1637_brightness_t brightness)
{
/* transmit the data command first */
_tm1637_start(dev);
int res = _tm1637_transmit_byte(dev, COMMAND_DATA);
if (res < 0) {
return -1;
}
_tm1637_stop(dev);
/**
* set the address using the auto increment mode for addresses and
* start at zero
*/
_tm1637_start(dev);
res = _tm1637_transmit_byte(dev, COMMAND_ADDRESS);
if (res < 0) {
return -1;
}
/* transmit each byte indiviudally */
for (int i = 0; i < DIGIT_COUNT; ++i) {
res = _tm1637_transmit_byte(dev, segments[i]);
if (res < 0) {
return -1;
}
}
_tm1637_stop(dev);
/* transmit the display state and the brightness */
_tm1637_start(dev);
res = _tm1637_transmit_byte(dev, COMMAND_DISPLAY_AND_CONTROL |
brightness | BIT_MASK_ON);
if (res < 0) {
return -1;
}
_tm1637_stop(dev);
return 0;
}
/**
* @brief Modifies the segments array to enable the colon
*
* @param[in,out] segments segments to enable the colon on
*/
inline static void _enable_colon(uint8_t *segments)
{
/* the digit to the left of the middle uses the colon */
segments[DIGIT_COUNT / 2 - 1] |= BIT_MASK_DOT;
}
int tm1637_init(tm1637_t *dev, const tm1637_params_t *params)
{
assert(params != NULL);
assert(dev != NULL);
assert(params->clk != GPIO_UNDEF);
assert(params->dio != GPIO_UNDEF);
/* set the parameters */
dev->params = params;
if (gpio_init(dev->params->clk, GPIO_OUT)) {
return -1;
}
if (gpio_init(dev->params->dio, GPIO_OUT)) {
return -1;
}
gpio_write(dev->params->clk, false);
gpio_write(dev->params->dio, false);
/**
* This is necessary as the display needs to warm-up to the clock speed.
* If the following lines are omitted, the display will generate a NACK after the first
* byte transmission.
*/
_tm1637_start(dev);
_tm1637_stop(dev);
return 0;
}
int tm1637_clear(const tm1637_t *dev)
{
uint8_t segments[DIGIT_COUNT] = { 0 };
return _tm1637_transmit_segments(dev, segments, TM1637_PW_1_16);
}
int tm1637_write_number(const tm1637_t *dev, int16_t number,
tm1637_brightness_t brightness, bool colon,
bool leading_zeros)
{
/* with only 4 digits available, this range can't be exceeded */
assert(number <= 9999);
assert(number >= -999);
uint8_t segments[DIGIT_COUNT] = { 0 };
if (number == 0) {
segments[DIGIT_COUNT - 1] = segments_array[0];
}
else if (number < 0) {
/* for a negative number invert the signedness */
number = -number;
for (int i = 0; i < DIGIT_COUNT; ++i) {
if (number != 0) {
segments[DIGIT_COUNT - 1 - i] = segments_array[number % 10];
number /= 10;
}
else if (!leading_zeros) {
/**
* without leading zeros, the minus sign is to the left of the most
* significant digit
*/
segments[DIGIT_COUNT - 1 - i] = minus_sign;
break;
}
else {
/* with leading zeros, the minus sign is always at the leftmost position */
segments[0] = minus_sign;
break;
}
}
}
else {
for (int i = 0; i < DIGIT_COUNT; ++i) {
if (number != 0) {
segments[DIGIT_COUNT - 1 - i] = segments_array[number % 10];
number /= 10;
}
}
}
/* fill out all segments that have not yet been filled with zeros */
if (leading_zeros) {
for (int i = 0; i < DIGIT_COUNT; ++i) {
if (segments[i] == 0) {
segments[i] = segments_array[0];
}
}
}
if (colon) {
_enable_colon(segments);
}
return _tm1637_transmit_segments(dev, segments, brightness);
}
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