HT1621 7 segment LCD Arduino library

Arduino library for 7-segment LCDs based on the HT1621 driver, with support for 4-digit displays and various low power modes. Often marked as PDC-6X1 (6-digits) or LCM0220 (4-digits).

Based on the bitbanging efforts by anxzhu (2016-2018).

APIs rewritten in 2018 to follow the LiquidCrystal format by valerionew.

Rewritten again by kreddkrikk with support for 4-digit displays and low power modes.

API reference

• void begin(int width, int cs_p, int wr_p, int data_p) Activate the display. Acceptable values for width are 6 for 6-digit displays and 4 for 4-digit displays.

• void begin(int width, int cs_p, int wr_p, int data_p, int backlight_p) Activate the display with backlight control.

• void powerDown() Power down the display. This reduces power consumption to <0.1uA.

• void powerUp() Bring the display out of power down status.

• void standBy() Turn off MCU pins, but keep the display active. This reduces power consumption by about 100uA. The display cannot be updated while in standby mode until active() is called.

• void active() Come out of standby mode to update the display.

• void clear() Clear the display.

• void lcdOn() Turn the display on.

• void lcdOff() Turn the display off.

• void backlightOn() Turn on the backlight.

• void backlightOff() Turn off the backlight.

• void print(const char* str) Base function for all other print functions.

• void print(double num, int precision) Print floating value, right-aligned.

• void print(int num) Print 16-bit integer, right-aligned.

• void print(long num) Print 32-bit integer, right-aligned.

• void printTemp(double num, char unit, bool degree) Print the temperature, optionally including degree symbol and unit. Set unit to NULL to hide the unit symbol.

• void printTime(bool pad, int num1, int num2) Print clock/timer number pair separated by colon or decimal, with the first number optionally padded by leading zeros.

• void printError(int err) Print an error code to the display.

• void batteryLevel(int level) Set the battery indicator.

Standby mode

Current draw for an active display can be reduced to ~100uA using standby mode and running the display from a 3.3V power source. If operating the display from a microcontroller running at <10uA, two AAA batteries (3.0V, 2400mAh) would theoretically power such a setup for ~2.5 years.