Micro Thermal Printer 5~9V Embedded Thermal Receipt Printer Serial Port Microcontroller Secondary Development MCU Printing Module TTL/RS232

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The media could not be loaded. This is the second thermal printer module I've played with (the first was MicroMall Maikrt Embedded Thermal Printer, which I also reviewed). Other than the color, this one appears to be identical to the other one, except that this one is 5-9V, whereas the other is 12-24V.One thing I will tell you if you decide to implement this printer (or any thermal printer): the lower the voltage, the higher the current it will draw. The documentation isn't clear about exactly how much current this printer will draw, but your project should be able to deliver at least 3A -- definitely do not try to power this from the 5V pin on your Arduino! If the printer can't draw enough current while printing, it'll be obvious because the text will be very light and washed out, and the green LED in the feed button will flicker.I use the "Adafruit-Thermal-Printer-Library" from GitHub in my Arduino project to drive this printer, which you don't need, as you can just `Serial.print()` directly to it without the library, but the library makes things a lot easier, such as setting text size, bold, underline, etc.One of the features of that library is a function to detect whether the paper is loaded or empty, although in the comments it does say that not every printer supports that command. Well, this worked on that other printer, but not on this one. Apparently the firmware is different? I've tried researching these printers to see if I can find firmware and other documentation, but it's a tightly-held secret, apparently. I guess I could reach out to the seller and ask.Also, as I described in my other review, this printer is capable of TTL-level or RS232-level UART, and if you plan to connect this to your Arduino or other microcontroller, you'll want TTL. The product listing says "the default is RS232. If you need to switch to TTL, you can contact us and we will tell you how to switch." I don't know why they want you to ask them instead of them just providing that information up-front, but there's a small hole in the bottom of the case that exposes a tiny slide switch on the PCB below. I'm guessing that's the magic TTL/RS232 switch, but it's unlabelled, so you actually have no way of knowing which way is which. Sure, the listing says "default is RS232," but is it really?The other printer I reviewed said the same thing about defaulting to RS232, but the document that came in the box said it was already in TTL mode. Are you confused yet? The tiny switch inside of this printer was set differently than the other one, so I assumed this one was actually in RS232 mode as stated, so I flipped the switch, and it's worked just fine without frying my ESP32.Overall, this is a great product that will serve you will for any project requiring a printer. I knocked off one star, as with the other printer I reviewed, for the confusion around the RS232/TTL modes and for not providing full documentation.