STC8H3K64S2 makes 12864LCD dual-channel voltage and current capacity meter

 Because I recently got a few 2 yuan cheap POS machine 12864 screens, I made a single-channel voltage and current capacity meter using a 20-pin TTSOP20 packaged STC8H3K64S2 microcontroller. The cost is about 2 yuan 5 to 2 yuan 9. The price is cheap and the size is small. After calculation, it has 5 ADC conversion pins. It is enough to make a dual-channel voltage and ammeter, and the remaining ADC can be used as a thermometer. So I looked for a program for an NTC thermometer online and finally found it. I copied it and added it to the firmware to use it. I added a 20-cent NTC resistor. Adding a thermometer to it gives you an additional temperature measurement function, which is a great value.

Because the original two-inch 12864 screen has been sold out, and I still have 10 screens on hand. I found another 1.4-inch POS machine with a 12860 screen online. The main control is also 7567. And with backlight, except for the different pin sequence, everything else is basically the same, and the driver is also the same.

It took a lot of effort to find the information on this screen, but I finally found it.
The 1.4-inch screen is silk-printed FM1721625 CT 6, and the main control IC7567
pins are arranged in the following order.

In order to facilitate imitation, when designing the board, I used 8 pins to lead out the LCD pins on the 1.4-inch board. Friends who have a 12864 screen compatible with the 7567 main control IC can directly use DuPont cable to connect the screen in their hand according to the markings on the silk screen. Just use this board.

What the back looks like. The match head on the top is NTC temperature measurement software, which costs two cents a piece. The thermometer firmware is added to the software. Can have thermometer function. Compared with the 18B20 temperature measurement on hand, the error does not exceed 1.5 degrees, which is okay. The one on the right is made of a 2.0-inch screen.

The first time you turn on the computer after flashing the firmware, if there is no calibration data in the eerom memory of the microcontroller, it will automatically enter the calibration state.


Press the SW1 key to calibrate the voltage zero point of the first channel, the voltage multiple of the first channel, the current zero point of the first channel, and the current multiple of the first channel; the voltage zero point of the second channel, the voltage multiple of the second channel, the current zero point of the second channel, and the current multiple of the second channel. circuit current multiple. When calibrating the corresponding item, the current or voltage should be input at the corresponding input terminal. Adjust the up and down key settings of SW2 and SW3 to make the value displayed by the voltage and ammeter consistent with the actual value. If there is a deviation in the displayed voltage and current after normal use. You can long press the SW1 key to enter the calibration program in the normal interface, and repeat the above steps to calibrate.

The circuit diagram is as follows. As long as you have a 7567 4-wire spi input and a 12864 screen, you should be able to use it. I led out the LCD 8 pins on the board. If you have a 7567 screen, it should be universal to connect these pins to the LCD screen.

When downloading the microcontroller, you must set it according to the picture below, and you can't make a mistake. If you make a mistake, it will not function properly. The main model of the microcontroller is the stc8H3K series, and any program space ROM larger than 32K is acceptable. I use this microcontroller model STC8H3K64S2-TTSOP20 mainly because it is cheap and has the largest program space. The size of the EEROM space can be adjusted at will when downloading the program.