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Open Source
sch,pcb,gerber file-->https://gitee.com/fiftyhz/BI1IZF/tree/m ... 74_HD44780
you can DIY PCB,Of course you can also buy the PCF8574 module.

• 1. Connect PCF8574 to Raspberry,VCC to VCC, SDA to SDA, SCL to SCL, GND to GND.The backlight cannot be controlled by PCF8574,
  it needs to be connected separately,Please check the schematic.

• 2. Determine the I2C address，use

  Code: Select all

  i2cdetect -y 1

• 3. set MMDVM Display Type is HD44780 and save

• 4. check configuration-Expert-MMDVMHost-HD44780 config，if you use pwm，change pwn 1,Apply Changes

this is my config

-----------------------------------------------------------------This is the dividing line---------------------------------------------------------

• Normally, the screen will display, if there is no display, try to adjust the screen contrast

• If you buy a PCF8574 module, you must check the connection between the module and HD44780. It must be the following, is very important

• If you use PWM ,connection RPI Pin 32(GPIO pin 12,Wiring Pi pin 26) to HD44780 Pin15,Pin16 to GND,RPI output current can drive the backlight, of course you can use a triode

If you do not use PCF8574, you also need to compile the file->https://github.com/g4klx/MMDVMHost/blob ... ME.HD44780
I can answer all questions about HD44780

73
BI1IZF

KE7FNS wrote: ↑Wed Sep 08, 2021 5:05 pm

BI1IZF wrote: ↑Wed Sep 08, 2021 2:11 pm

• 1. Enable I2C,-->https://learn.sparkfun.com/tutorials/ra ... #i2c-on-pi

i2c is already enabled in Pi-Star.

BI1IZF wrote: ↑Wed Sep 08, 2021 2:11 pm sudo make Makefile.Pi.PCF8574

You shouldn't have to build a custom MMDVMHost, Pi-Star is already configured to work with a HD44780.

Thank you for your answer
I saw in the G4KLX document that it needs to be compiled, but it is not needed, which makes the operation easier。