HT1621 7 segment LCD library

Library for 7-segment lcds based on the HT1621 driver. Very often marked as PDC-6X1.

Based on the bitbanging efforts by anxzhu (2016-2018). APIs rewritten in 2018 to follow the LiquidCrystal format by [valerio\new] (https://github.com/5N44P).

Refactored. Removed dependency on any MCU hardware. Added SPI support and text support. By Viacheslav Balandin https://github.com/hedgehogV/HT1621-lcd

APIs reference

• HT1621(pPinSet *pCs, pPinSet *pSck, pPinSet *pMosi, pPinSet *pBacklight) Ctor. Starts the lcd with the pin assignment declared. The backlight pin is optional

• HT1621(pInterface *pSpi, pPinSet *pCs, pPinSet *pBacklight) Starts the lcd with SPI interface. CS and backlight pins are optional. Tested with CPOL=LOW, EDGE=1

• void clear() Clears the display

• void backlightOn() Turns on the backlight

• void backlightOff() Turns off the backlight

• void batteryLevel(uint8_t percents) Accepts values from 0 to 100. Bigger values will be treated as 100. Battery charge represented by the rectangles above the battery symbol.

• void print(const char *str) Print string (up to 6 characters) Allowed characters: letters, digits, space, minus, underscore. Not allowed characters will be displayed as spaces. See characters appearance in Internal functioning chapter

• void print(int32_t num) Prints a signed integer between -99999 and 999999. Larger and smaller values will be displayed as -99999 and 999999

• void print(float num, int precision) Prints a float with 0 to 3 decimals, based on the precision parameter. Default value is 3

• void print(int32_t multiplied_float, uint32_t multiplier) Prints number with dot. Use it instead float. Float type usage may slow down many systems

• void displayOff() Turns off the display (doesn't turn off the backlight)

• void displayOn() Turns the display back on after it has been disabled by noDisplay()

API usage

To start display you have to call one of Ctors with pointers to toggle_Gpio or SpiTx functions. You may need a function wrapper. Wrapper example:

// spi wrapper
void SpiTx(uint8_t *ptr, uint8_t size)
{
  HAL_SPI_Transmit(&hspi2, ptr, size, 2000);
}

// cs wrapper
void toggle_CS(bool b)
{
  HAL_GPIO_WritePin(CS_GPIO_Port, CS_Pin, b? GPIO_PIN_SET:GPIO_PIN_RESET);
}

// ctor call example
HT1621 lcd = HT1621(&SpiTx, &toggle_CS);

// prints "hello" on display
lcd.print("HELLO");

Internal functioning

Letters example. Source: https://www.dcode.fr/7-segment-display Some of them looks a bit strange. But 7-segment display isn't the best thing to show letters

° -> 0x33 = 10 + 20 + 01 + 02 C -> 0x1D = 10 + 01 + 04 + 08

  ___10___
 |        |
 01       20
 |___02___|
 |        |
 04       40
 |___08___|