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drivers: auxdisplay: Add driver for common 7-segment display
This commit introduces a new driver for a common GPIO-driven 7-segment display. supporting both common anode and common cathode configurations. Signed-off-by: Chen Xingyu <hi@xingrz.me>
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‎drivers/auxdisplay/CMakeLists.txt

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@@ -4,6 +4,7 @@ zephyr_syscall_header(${ZEPHYR_BASE}/include/zephyr/drivers/auxdisplay.h)
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zephyr_library()
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zephyr_library_sources_ifdef(CONFIG_USERSPACE auxdisplay_handlers.c)
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zephyr_library_sources_ifdef(CONFIG_AUXDISPLAY_GPIO_7SEG auxdisplay_gpio_7seg.c)
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zephyr_library_sources_ifdef(CONFIG_AUXDISPLAY_HD44780 auxdisplay_hd44780.c)
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zephyr_library_sources_ifdef(CONFIG_AUXDISPLAY_ITRON auxdisplay_itron.c)
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zephyr_library_sources_ifdef(CONFIG_AUXDISPLAY_JHD1313 auxdisplay_jhd1313.c)

‎drivers/auxdisplay/Kconfig

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@@ -20,6 +20,7 @@ module = AUXDISPLAY
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module-str = auxdisplay
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source "subsys/logging/Kconfig.template.log_config"
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source "drivers/auxdisplay/Kconfig.gpio"
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source "drivers/auxdisplay/Kconfig.hd44780"
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source "drivers/auxdisplay/Kconfig.itron"
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source "drivers/auxdisplay/Kconfig.jhd1313"

‎drivers/auxdisplay/Kconfig.gpio

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# Copyright (c) 2024-2025 Chen Xingyu <hi@xingrz.me>
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# SPDX-License-Identifier: Apache-2.0
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config AUXDISPLAY_GPIO_7SEG
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bool "Common GPIO-driven 7-Segment Display"
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default y
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depends on DT_HAS_GPIO_7_SEGMENT_ENABLED
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select GPIO

‎drivers/auxdisplay/auxdisplay_gpio_7seg.c

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/*
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* Copyright (c) 2024-2025 Chen Xingyu <hi@xingrz.me>
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* SPDX-License-Identifier: Apache-2.0
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*/
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#define DT_DRV_COMPAT gpio_7_segment
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#include <zephyr/device.h>
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#include <zephyr/kernel.h>
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#include <zephyr/drivers/auxdisplay.h>
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#include <zephyr/drivers/gpio.h>
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#include <zephyr/logging/log.h>
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LOG_MODULE_REGISTER(auxdisplay_gpio_7seg, CONFIG_AUXDISPLAY_LOG_LEVEL);
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static const uint8_t DIGITS[] = {
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[0] = BIT(0) | BIT(1) | BIT(2) | BIT(3) | BIT(4) | BIT(5),
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[1] = BIT(1) | BIT(2),
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[2] = BIT(0) | BIT(1) | BIT(3) | BIT(4) | BIT(6),
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[3] = BIT(0) | BIT(1) | BIT(2) | BIT(3) | BIT(6),
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[4] = BIT(1) | BIT(2) | BIT(5) | BIT(6),
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[5] = BIT(0) | BIT(2) | BIT(3) | BIT(5) | BIT(6),
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[6] = BIT(0) | BIT(2) | BIT(3) | BIT(4) | BIT(5) | BIT(6),
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[7] = BIT(0) | BIT(1) | BIT(2),
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[8] = BIT(0) | BIT(1) | BIT(2) | BIT(3) | BIT(4) | BIT(5) | BIT(6),
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[9] = BIT(0) | BIT(1) | BIT(2) | BIT(3) | BIT(5) | BIT(6),
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};
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#define DP (BIT(7))
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#define BLANK (0x00)
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struct auxdisplay_gpio_7seg_data {
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struct k_timer timer;
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uint32_t refresh_pos;
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int16_t cursor_x;
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int16_t cursor_y;
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};
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struct auxdisplay_gpio_7seg_config {
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struct auxdisplay_capabilities capabilities;
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const struct gpio_dt_spec *segment_gpios;
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const struct gpio_dt_spec *digit_gpios;
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uint32_t segment_count;
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uint32_t digit_count;
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uint32_t refresh_period_ms;
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uint8_t *buffer;
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};
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static int auxdisplay_gpio_7seg_display_on(const struct device *dev)
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{
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const struct auxdisplay_gpio_7seg_config *cfg = dev->config;
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struct auxdisplay_gpio_7seg_data *data = dev->data;
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data->refresh_pos = 0;
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k_timer_start(&data->timer, K_NO_WAIT, K_MSEC(cfg->refresh_period_ms));
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return 0;
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}
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static int auxdisplay_gpio_7seg_display_off(const struct device *dev)
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{
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struct auxdisplay_gpio_7seg_data *data = dev->data;
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k_timer_stop(&data->timer);
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return 0;
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}
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static int auxdisplay_gpio_7seg_cursor_position_set(const struct device *dev,
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enum auxdisplay_position type, int16_t x,
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int16_t y)
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{
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const struct auxdisplay_gpio_7seg_config *cfg = dev->config;
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struct auxdisplay_gpio_7seg_data *data = dev->data;
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if (type == AUXDISPLAY_POSITION_RELATIVE) {
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x += data->cursor_x;
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y += data->cursor_y;
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} else if (type == AUXDISPLAY_POSITION_RELATIVE_DIRECTION) {
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return -EINVAL;
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}
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if (x < 0 || y < 0) {
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return -EINVAL;
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} else if (x >= cfg->capabilities.columns || y >= cfg->capabilities.rows) {
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return -EINVAL;
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}
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data->cursor_x = x;
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data->cursor_y = y;
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return 0;
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}
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static int auxdisplay_gpio_7seg_cursor_position_get(const struct device *dev, int16_t *x,
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int16_t *y)
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{
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struct auxdisplay_gpio_7seg_data *data = dev->data;
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*x = data->cursor_x;
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*y = data->cursor_y;
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return 0;
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}
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static int auxdisplay_gpio_7seg_capabilities_get(const struct device *dev,
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struct auxdisplay_capabilities *capabilities)
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{
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const struct auxdisplay_gpio_7seg_config *cfg = dev->config;
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memcpy(capabilities, &cfg->capabilities, sizeof(struct auxdisplay_capabilities));
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return 0;
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}
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static int auxdisplay_gpio_7seg_clear(const struct device *dev)
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{
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const struct auxdisplay_gpio_7seg_config *cfg = dev->config;
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struct auxdisplay_gpio_7seg_data *data = dev->data;
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memset(cfg->buffer, 0, cfg->digit_count);
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data->refresh_pos = 0;
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data->cursor_x = 0;
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data->cursor_y = 0;
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return 0;
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}
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static int auxdisplay_gpio_7seg_write(const struct device *dev, const uint8_t *ch, uint16_t len)
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{
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const struct auxdisplay_gpio_7seg_config *cfg = dev->config;
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struct auxdisplay_gpio_7seg_data *data = dev->data;
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uint32_t i, cursor;
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for (i = 0; i < len; i++) {
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cursor = data->cursor_y * cfg->capabilities.columns + data->cursor_x;
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/*
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* Special case where the decimal point should be added to the
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* previous digit
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*/
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if (ch[i] == '.' && cursor > 0) {
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cfg->buffer[cursor - 1] |= DP;
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continue;
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}
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if (cursor >= cfg->digit_count) {
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break;
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}
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if (ch[i] >= '0' && ch[i] <= '9') {
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cfg->buffer[cursor] = DIGITS[ch[i] - '0'];
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} else if (ch[i] == '.') {
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/* Leading dot, leave the digit blank */
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cfg->buffer[cursor] = DP;
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} else {
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cfg->buffer[cursor] = BLANK;
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}
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/* Move the cursor */
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if (data->cursor_x < cfg->capabilities.columns - 1) {
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data->cursor_x++;
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} else if (data->cursor_y < cfg->capabilities.rows - 1) {
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data->cursor_x = 0;
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data->cursor_y++;
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}
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}
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/* Reset the refresh position */
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data->refresh_pos = 0;
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return 0;
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}
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static void auxdisplay_gpio_7seg_timer_expiry_fn(struct k_timer *timer)
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{
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const struct device *dev = k_timer_user_data_get(timer);
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const struct auxdisplay_gpio_7seg_config *cfg = dev->config;
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struct auxdisplay_gpio_7seg_data *data = dev->data;
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/* Turn off the current digit and move to the next one */
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gpio_pin_set_dt(&cfg->digit_gpios[data->refresh_pos], 0);
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data->refresh_pos = (data->refresh_pos + 1) % cfg->digit_count;
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/* Set the segments for the new digit */
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for (uint32_t i = 0; i < cfg->segment_count; i++) {
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gpio_pin_set_dt(&cfg->segment_gpios[i], cfg->buffer[data->refresh_pos] & BIT(i));
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}
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/* Turn on the new digit */
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gpio_pin_set_dt(&cfg->digit_gpios[data->refresh_pos], 1);
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}
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static void auxdisplay_gpio_7seg_timer_stop_fn(struct k_timer *timer)
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{
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const struct device *dev = k_timer_user_data_get(timer);
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const struct auxdisplay_gpio_7seg_config *cfg = dev->config;
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/* Turn off all digits */
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for (uint32_t i = 0; i < cfg->digit_count; i++) {
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gpio_pin_set_dt(&cfg->digit_gpios[i], 0);
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}
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}
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static int auxdisplay_gpio_7seg_init(const struct device *dev)
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{
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const struct auxdisplay_gpio_7seg_config *cfg = dev->config;
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struct auxdisplay_gpio_7seg_data *data = dev->data;
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for (uint32_t i = 0; i < cfg->segment_count; i++) {
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gpio_pin_configure_dt(&cfg->segment_gpios[i], GPIO_OUTPUT_INACTIVE);
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}
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for (uint32_t i = 0; i < cfg->digit_count; i++) {
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gpio_pin_configure_dt(&cfg->digit_gpios[i], GPIO_OUTPUT_INACTIVE);
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}
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k_timer_init(&data->timer, auxdisplay_gpio_7seg_timer_expiry_fn,
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auxdisplay_gpio_7seg_timer_stop_fn);
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k_timer_user_data_set(&data->timer, (void *)dev);
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auxdisplay_gpio_7seg_display_on(dev);
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return 0;
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}
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static DEVICE_API(auxdisplay, auxdisplay_gpio_7seg_api) = {
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.display_on = auxdisplay_gpio_7seg_display_on,
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.display_off = auxdisplay_gpio_7seg_display_off,
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.cursor_position_set = auxdisplay_gpio_7seg_cursor_position_set,
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.cursor_position_get = auxdisplay_gpio_7seg_cursor_position_get,
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.capabilities_get = auxdisplay_gpio_7seg_capabilities_get,
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.clear = auxdisplay_gpio_7seg_clear,
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.write = auxdisplay_gpio_7seg_write,
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};
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#define AUXDISPLAY_GPIO_7SEG_INST(n) \
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static struct auxdisplay_gpio_7seg_data auxdisplay_gpio_7seg_data_##n; \
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\
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static const struct gpio_dt_spec auxdisplay_gpio_7seg_segment_gpios_##n[] = { \
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DT_INST_FOREACH_PROP_ELEM_SEP(n, segment_gpios, GPIO_DT_SPEC_GET_BY_IDX, (,))}; \
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\
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static const struct gpio_dt_spec auxdisplay_gpio_7seg_digit_gpios_##n[] = { \
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DT_INST_FOREACH_PROP_ELEM_SEP(n, digit_gpios, GPIO_DT_SPEC_GET_BY_IDX, (,))}; \
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\
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static uint8_t auxdisplay_gpio_7seg_buffer_##n[DT_INST_PROP_LEN(n, digit_gpios)]; \
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\
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static const struct auxdisplay_gpio_7seg_config auxdisplay_gpio_7seg_config_##n = { \
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.capabilities = \
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{ \
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.columns = DT_INST_PROP(n, columns), \
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.rows = DT_INST_PROP(n, rows), \
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}, \
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.segment_gpios = auxdisplay_gpio_7seg_segment_gpios_##n, \
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.segment_count = DT_INST_PROP_LEN(n, segment_gpios), \
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.digit_gpios = auxdisplay_gpio_7seg_digit_gpios_##n, \
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.digit_count = DT_INST_PROP_LEN(n, digit_gpios), \
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.refresh_period_ms = DT_INST_PROP(n, refresh_period_ms), \
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.buffer = auxdisplay_gpio_7seg_buffer_##n, \
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}; \
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\
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DEVICE_DT_INST_DEFINE(n, auxdisplay_gpio_7seg_init, NULL, &auxdisplay_gpio_7seg_data_##n, \
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&auxdisplay_gpio_7seg_config_##n, POST_KERNEL, \
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CONFIG_AUXDISPLAY_INIT_PRIORITY, &auxdisplay_gpio_7seg_api);
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DT_INST_FOREACH_STATUS_OKAY(AUXDISPLAY_GPIO_7SEG_INST)

‎dts/bindings/auxdisplay/gpio-7-segment.yaml

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# Copyright (c) 2024-2025 Chen Xingyu <hi@xingrz.me>
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# SPDX-License-Identifier: Apache-2.0
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description: |
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Common GPIO-driven 7-Segment Display
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A 7-segment display is a form of electronic display device for displaying
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decimal numerals that is an alternative to the more complex dot matrix
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displays. Seven-segment displays are widely used in digital clocks, electronic
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meters, basic calculators, and other electronic devices that display numerical
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information.
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This driver supports 7-segment displays driven by GPIOs, in a widely used
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circuit design either common anode or common cathode.
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In common anode design, digit-gpios and segment-gpios are configured as active
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high and active low respectively, meaning that the current flows from
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digit-gpios to segment-gpios. Vice versa for common cathode.
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Example:
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#include <zephyr/dt-bindings/gpio/gpio.h>
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/ {
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auxdisplay_0: digi-display {
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compatible = "gpio-7-segment";
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columns = <3>;
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rows = <1>;
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segment-gpios = <&gpio0 0 GPIO_ACTIVE_LOW>, /* A */
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<&gpio0 1 GPIO_ACTIVE_LOW>, /* B */
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<&gpio0 2 GPIO_ACTIVE_LOW>, /* C */
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<&gpio0 3 GPIO_ACTIVE_LOW>, /* D */
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<&gpio0 4 GPIO_ACTIVE_LOW>, /* E */
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<&gpio0 5 GPIO_ACTIVE_LOW>, /* F */
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<&gpio0 6 GPIO_ACTIVE_LOW>, /* G */
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<&gpio0 7 GPIO_ACTIVE_LOW>; /* DP */
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digit-gpios = <&gpio1 0 GPIO_ACTIVE_HIGH>, /* DIG1 */
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<&gpio1 1 GPIO_ACTIVE_HIGH>, /* DIG2 */
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<&gpio1 2 GPIO_ACTIVE_HIGH>; /* DIG3 */
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refresh-period-ms = <1>;
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};
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};
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compatible: "gpio-7-segment"
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include: auxdisplay-device.yaml
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properties:
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segment-gpios:
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type: phandle-array
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required: true
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description: |
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GPIOs used to control the segments.
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Segments are usually labeled A to G, and DP for the decimal point. The
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GPIOs must be listed in the order A, B, C, D, E, F, G and an optional DP.
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The following diagram shows the segment layout:
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-- A --
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| |
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F B
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| |
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-- G --
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| |
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E C
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| |
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-- D -- (DP)
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The number of GPIOs must be 7 for a 7-segment display, or 8 for a 7-segment
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display with a decimal point.
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digit-gpios:
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type: phandle-array
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required: true
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description: |
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GPIOs used to control the digits (the common anodes or cathodes).
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The number of GPIOs must match the number of digits.
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refresh-period-ms:
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type: int
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required: true
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description: |
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The refresh period in milliseconds.
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This is the time between the display of each digit. The refresh period
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must be long enough to allow the segments to be driven and the digit to
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be selected.

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