Xiao Zhang, who had just taken over the maintenance of the shopping mall information screen, stared at the red-text display with a flash of "Welcome" and was sweating. The manager asked him to update the promotional information, but he couldn't even find the USB port. Have you encountered this kind of scenario? Don’t worry, today we will break it up and talk about the ways to change the word in monochrome screens.

​​First, you have to confirm where the "brain" of the display is​​
More than 90% of the monochrome screen control cards are hidden in three places:

1. Inside the waterproof cover on the top of the screen (commonly found in outdoor screens)
2. The side slot of the power box (there are mostly used in this design in the shopping mall hanging screen)
3. Independent control box (installed separately from the display screen)

Last week, an electrician in the supermarket mistakenly thought the control card was the router restart button, and the entire screen was garbled for two hours. Remember this feature:​ ​Green circuit board with serial port​​, usually with the words HUB on it, don’t admit it wrong.

​​The data cable is the key​​
Finding the control card is only the first step, the focus depends on the interface type:

• Old-style round-mouth PS/2 interface (common screens before 2008)
• Nine-pin serial port (the most common COM port)
• Network port (smart screen that supports TCP/IP protocol)

Here is a lesson learned from blood and tears: a property guy held his mobile phone data cable for a long time, but he turned all the interface pins. The three-piece set that must be changed should be:​ ​USB to serial cable, 232 converter, 5V power adapter​​, none of them is missing.

​​Software matching is more important than you think​​
Any errors reported after the five characters were added? Eighty-mostly, I didn’t understand the control card model. Teach you how to find out:
① Open the control card cover to see the chip logo. Common ones include HD-M/L series
② Note the display size (such as Φ3.75) and the number of pixels
③ Confirm whether the communication protocol is UART or SPI

Last year, a hospital made a joke about the diagnosis screen, which was because it used incompatible software to cause Chinese characters to become garbled. Now mainstream software supports​ ​Automatically identify baud rate​​, adjust the communication parameters to 9600bps, N81 mode and can basically be connected.

Suddenly I thought of a key question: Why are half of the characters displayed incompletely after changing them? This involves​ ​Pixel point matching​​. For example: If the screen with a 16×32 dot matrix is set to 17 points, it will inevitably cut off. Remember this formula:​ ​Text height = number of lines × dot spacing​​For example, for an 8-line screen with dot spacing is 16mm, then the height of the text must be 128mm.

​​Is it really reliable to change the font on your mobile phone? ​ ​
Many masters now recommend Bluetooth word change modules, and the actual test data will be used for your reference:

If you change the content every day, it is recommended to use traditional wired methods. But if you have temporary emergency, buy one​ ​Mobile phone with OTG function + USB adapter​​It can be done with it, remember to install the LED word modification APP on your Android phone in advance.

Some readers asked: Should we cut off the power when changing the word? This matter is divided into situations:

• Power must be cut off when connecting the data cable!
• Can be operated with live during debugging
• Keep power supply when burning the program

The most powerful operation I have ever seen is that an electrician plugs and unplugs the serial port cable with electricity, and the control chip directly smokes. For safety reasons, prepare one​ ​Electrician tape with indicator light​​, it is correct to measure the voltage before wiring.

Finally, let me tell you a cold knowledge: monochrome screens can also play animation effects! pass​ ​Frame-by-frame refresh control​​, can fully produce special effects such as marquee lanterns, flashing warnings, etc. There is a parking lot that makes the "remaining parking spaces" numbers jump, and the recognition of customer feedback has increased by 60%. However, be careful not to refresh rate exceeds 200Hz, otherwise you will see strobes with your naked eyes.

The editor thinks that instead of looking for a master to change his words, it is better to prepare a set by yourself.​​Portable font-changing tool kit​​. It can be done with 200 yuan on Taobao, including a universal control card detector, a multi-protocol conversion head and anti-static gloves. Next time I encounter a display strike, I can at least determine whether it is a control card problem first. Isn’t it good to save 300 yuan on-site inspection fees?

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