AirMeter: Stream an AN870 Multimeter’s LCD to Your Browser

AirMeter：将 AN870 万用表的 LCD 屏幕实时串流至浏览器

Want live multimeter readings on screen during a build video without fighting glare, focus hunt, and awkward camera angles? You can, and the parts list is short: an ANENG AN870 meter (any clone built on the DTM0660 chip works), an RP2040 board to sit inside it, a pair of 433 MHz HC-12 radios, an ESP32-C3 to host the page, and one small comparator board you will make yourself. 在制作视频时，想要在屏幕上实时显示万用表读数，却不想面对反光、对焦困难和尴尬的拍摄角度吗？你可以做到，而且所需的零件清单很短：一台 ANENG AN870 万用表（任何基于 DTM0660 芯片的克隆版均可）、一块内置的 RP2040 开发板、一对 433 MHz HC-12 无线电模块、一个用于托管网页的 ESP32-C3，以及一块你需要自制的小型比较器电路板。

YouTuber Bits und Bolts got tired of those filming headaches and built AirMeter, an open-source mod that taps the meter’s own LCD signals and redraws the display live in a web browser or as an OBS source. No proprietary app, no cloud account, no soldering to a hidden data port that may not even exist. YouTuber Bits und Bolts 受够了这些拍摄上的麻烦，于是打造了 AirMeter。这是一个开源改装项目，它能直接获取万用表自身的 LCD 信号，并在网页浏览器或 OBS 信号源中实时重绘显示内容。无需专用应用程序，无需云端账户，也不必去焊接可能根本不存在的隐藏数据接口。

Reading a screen that does not want to be read: That last point is where the project gets clever. The AN870 has a hidden UART, but the manufacturer left the processor pin it needs disconnected under a blob of epoxy, so serial access was a dead end. Instead, the RP2040 samples the signals that drive the LCD directly. That display is a 4x15 multiplexed matrix: 60 individual segments controlled through only 19 physical traces. Those lines do not carry clean digital logic, they carry four-level analog waveforms, so a custom board populated with five LM339 comparators squares them into levels a microcontroller can actually read. 读取一块“不愿被读取”的屏幕：最后一点正是该项目巧妙之处。AN870 虽然有一个隐藏的 UART 接口，但制造商将其所需的处理器引脚断开并封在环氧树脂胶滴下，因此串口访问是一条死胡同。取而代之的是，RP2040 直接采样驱动 LCD 的信号。该显示屏是一个 4x15 的多路复用矩阵：通过仅 19 条物理线路控制 60 个独立段。这些线路传输的不是纯净的数字逻辑信号，而是四电平模拟波形，因此需要一块搭载五个 LM339 比较器的定制电路板，将它们整形为微控制器能够读取的电平。

Once the RP2040 has clean signals, it decodes each digit, decimal point, and unit icon, then sends the reading over a low-power HC-12 link at 433 MHz to the ESP32-C3 receiver. The ESP32-C3 serves a tiny web page that faithfully rebuilds the meter’s LCD in any browser on your network. 一旦 RP2040 获得了清晰的信号，它就会解码每一个数字、小数点和单位图标，然后通过 433 MHz 的低功耗 HC-12 链路将读数发送给 ESP32-C3 接收器。ESP32-C3 会托管一个微型网页，在您网络内的任何浏览器中忠实地还原万用表的 LCD 显示。

The part you would repeat for your own meter: The tedious step is mapping the matrix. Bits und Bolts probed every common (COM) and segment (SEG) line with an oscilloscope and a test jig, matching each trace to the digit or icon it lights. Do that once and the firmware knows where every reading lives. Because the same DTM0660 chip hides inside a lot of budget meters, the method ports to more than just the AN870, you just re-map the segments. 你需要为自己的万用表重复的步骤：最繁琐的一步是映射矩阵。Bits und Bolts 使用示波器和测试夹具探测了每一条公共端 (COM) 和段端 (SEG) 线路，将每条线路与它所点亮的数字或图标对应起来。只要完成一次，固件就能知道每个读数的位置。由于许多廉价万用表内部都隐藏着同样的 DTM0660 芯片，这种方法不仅适用于 AN870，你只需要重新映射段位即可。

Schematics, board files, and firmware are on the build page: https://www.hackster.io/news/this-modded-multimeter-streams-its-screen-straight-to-your-browser-c46d844be09b 原理图、电路板文件和固件请见项目页面：https://www.hackster.io/news/this-modded-multimeter-streams-its-screen-straight-to-your-browser-c46d844be09b