NOYITO TTL to RS232 Module TTL RS232 Mutual Conversion Module Serial Level Conversion to SP232 for MCU, ARM, FPGA, Arduino, etc. TTL Serial Port communicates with RS232 Level Device

These are my go-to parts for TTL-RS232 conversion: they work really well, and they aren't attached to a DE-9 connector I usually don't need. They've been very reliable and easy to work with on Arduino, Pi and BeagleBone, and the price is certainly right. The silkscreen legends are clear and super helpful: no need to search the web for the pinouts, though the chip's data sheet is detailed and useful and can be worth a scan. Somebody asked if it does full +/- 12v on the RS232 lines, and it definitely does not: the chip isn't designed to have a 24v swing in the output circuits. The boards I have are based on the Sipex SP3232E chip, whose data sheet says max output swing +/- 13v, which is what i see. This scope trace shows the TX output line of a 19200bps signal with an amplitude of +5.9v to -5.7v, which is pretty much par for the course with a 5v supply. Using a 3.3v supply drops this only slightly (+5.8 to -5.6v on my boards), and all of this is plenty good for RS232. The ripple in the highs and lows are likely correlated with charge pump activity, and this isn't any problem for RS232 either.

Works great! Used in a project to connect a pi to a renogy wanderer charge controller. LEDs are handy for troubleshooting. Little pricey but does the job. Be aware there are counterfeit RS232 chips out there. Had purchased a different module, it ran hot and consumed 200 mA doing nothing. Turned out the chip had missing internal pull up resistors (and who knows what else).

Used this to read data from my inverters RS232 port, using wemos d1 mini and publish the data to MQTT broker. I bought several others while writing the code for the wemos and trying to get data from inverter. This one has got power, transfer and receive lights which comes handy troubleshooting the code. Finally got a response from the inverter and this converter works just fine. I visually see when the command is sent to inverter and the response received back from it. I also like that this has got nice leads that you can solder the wires, as well as holes to integrate it on a PCB if needed. Overall a great product.

Using this with an Atomic PI (x86 Atom, not ARM) to talk to a Renogy Solar Charge controller. Had to open the renogy to determine the pin layout but after that was easy to connect to the PI's UART GPIO pins. This thing is really small. You're best off soldering wires to the flat surfaces and not the holes imho. There are 2 LEDs on this device. One is always on (power) and the other goes on when there's data being sent (at least it's not on all the time).

This works just as it should, is compact, and is very clear on what wires go where. Adding pin terminals was easy.