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Fix wait periods for MCUs with tick period > 1ms #1

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Fix wait periods for MCUs with tick period > 1ms #1

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20 changes: 13 additions & 7 deletions main/lcd.c
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Original file line number Diff line number Diff line change
Expand Up @@ -5,15 +5,24 @@ static i2c_master_dev_handle_t i2c_device_handle = NULL;
static i2c_master_bus_handle_t i2c_bus_handle = NULL;
static uint8_t lcd_backlight_status = LCD_BACKLIGHT;

// Helper function to wait for a period with higher granularity
// than a tick while LCD completes its commands
static void wait_lcd_cycles(uint16_t cycles) {
// if esp32 is 100x faster than the lcd clock speed, then this loop runs 100 * cycles
for( volatile int i = 0; i < (configCPU_CLOCK_HZ/I2C_MASTER_FREQ_HZ) * cycles; i++ ) {
__asm__( "nop" ); // Do nothing, just waste time counting
}
}

// Helper function to toggle the enable bit
static esp_err_t i2c_transmit_with_enable_toggle(uint8_t data) {
uint8_t data_with_enable = data | LCD_ENABLE;
ESP_ERROR_CHECK(i2c_master_transmit(i2c_device_handle, &data_with_enable, 1, -1));
vTaskDelay(pdMS_TO_TICKS(1));
wait_lcd_cycles(2);

data_with_enable &= ~LCD_ENABLE;
ESP_ERROR_CHECK(i2c_master_transmit(i2c_device_handle, &data_with_enable, 1, -1));
vTaskDelay(pdMS_TO_TICKS(1));
wait_lcd_cycles(2);

return ESP_OK;
}
Expand All @@ -26,7 +35,6 @@ static esp_err_t i2c_send_byte_on_4bits(uint8_t data, uint8_t rs) {
};
ESP_ERROR_CHECK(i2c_transmit_with_enable_toggle(nibbles[0]));
ESP_ERROR_CHECK(i2c_transmit_with_enable_toggle(nibbles[1]));
vTaskDelay(pdMS_TO_TICKS(1));
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@kindlehl kindlehl Mar 31, 2026

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with the wait inside i2c_transmit_with_enable_toggle, this wait is not really doing anything.

ESP_LOGI(TAG, "I2C device data sent: 0x%02X", data);

return ESP_OK;
Expand All @@ -52,7 +60,7 @@ void i2c_master_init(void) {
};
ESP_ERROR_CHECK(i2c_master_bus_add_device(i2c_bus_handle, &i2c_device_config, &i2c_device_handle));
ESP_LOGI(TAG, "I2C device added");
vTaskDelay(pdMS_TO_TICKS(50)); // Wait for LCD to power up
vTaskDelay(pdMS_TO_TICKS(50) + 1); // Wait for LCD to power up
ESP_LOGI(TAG, "I2C device initialized");
}

Expand All @@ -78,12 +86,10 @@ void lcd_init(void) {

for (uint8_t i = 0; i < sizeof(init_8bit_commands); i++) {
ESP_ERROR_CHECK(i2c_transmit_with_enable_toggle(init_8bit_commands[i]));
vTaskDelay(pdMS_TO_TICKS(5));
}

for (uint8_t i = 0; i < sizeof(init_commands); i++) {
ESP_ERROR_CHECK(i2c_send_byte_on_4bits(init_commands[i], LCD_RS_CMD));
vTaskDelay(pdMS_TO_TICKS(5));
}
}

Expand All @@ -108,7 +114,7 @@ void lcd_write_string(const char *str) {
void lcd_clear(void) {
uint8_t data = 0b00000001;
ESP_ERROR_CHECK(i2c_send_byte_on_4bits(data, LCD_RS_CMD));
vTaskDelay(pdMS_TO_TICKS(2));
wait_lcd_cycles(310);
}

// Control the LCD backlight
Expand Down