HL-D812D VFD Clock

# HL-D812D 8-digit meter glass VFD screen driver board
> Zhixin's VFD 10 yuan screen has no information. This article will introduce how to drive and light up this VFD screen, and then we will draw a PCB to make it into a WIFI desktop clock

## Introduction
This VFD has an 8-digit meter field display, and the price is cheap, only 10 yuan. Friends who need it can place an order to buy it by themselves.
![image-lnzl.png]
The size is actually not big, it is still relatively small. The color after lighting is blue, the brightness is considerable, the contrast is higher than LED, and the visibility is clear at any angle. This is also the advantage of VFD. The only thing is that it is relatively power-consuming.

## The production plan
is based on the principle of small and light, and the drive plan adopts a transformer-free design.
The driver chip will use a professional VFD driver IC selection: PT6315

negative voltage boost -30V chip selection MC34063 This chip can boost and lower voltage, and can also boost negative voltage. Chip document: PDF document

AC driver will make the VFD brightness more uniform. The driver chip selected is the motor driver chip MX612E. It needs to cooperate with the input of the PWM signal.
The measured PWM signal is the best with a duty cycle of 50% and a frequency of 10000hz.

The MCU selected is the cost-effective ESP07-S. Other series of ESP8266 can also be used.
Design the CH340C automatic download circuit to facilitate the computer to burn and debug the program. Expand an LED indicator to facilitate debugging and later expansion.
Finally, 3 buttons are introduced to realize some user-defined function feedback.

#### Note
** It should be noted that the replica partners are advised to change the 3.3V LDO voltage regulation scheme.
The current problem found is that the computer USB cannot drive the VFD without display, and the charger can drive the display. There is no problem with downloading. My debugging method is: plug the charger into the type-c docking station, then connect the board, and finally plug the docking station into the computer to debug and see the effect**

### Open source code
** The code structure is divided into**
The pt6315.h API file only operates various register commands.
The gui.h API file operation interface display, the use of custom fonts.
mian.cpp calls the API method of gui.h to complete the display content rendering.

Although it is the code developed by Arduino, the library files pt6315.h and gui.h are completely written in C without C++ features. Macro definitions are used in .h to operate IO. It is highly portable. According to the ported platform, you only need to define the initialization of IO.

Github: [https://github.com/ccy-studio/ESP-VFD-PT6315](https://github.com/ccy-studio/ESP-VFD-PT6315)

### Functions implemented
- WIFI network configuration uses AP-Web mode and uses WifiMamge library
- Custom font
library - Clock display
- Key control to switch Page display content
- Year, month, day yyyy MM dd
- Hours and minutes HH:mm
- Hours, minutes, seconds HH:mm:ss
- Long press the button to clear the WIFI connection information configuration

### Actual picture
> Mobile phone shooting - The brightness effect is OK, but not very satisfactory.
> This VFD is not cost-effective and is not recommended for purchase. The price of 10 yuan is not worth it.

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