Smarter Serial Communications with WiSer

Surely you’ve been there: you need to capture serial output from a microcontroller or other device, so you reach for a PL2303 or CP210x or FT232RL-based USB-to-TTL serial cable (if you can remember where you put the damn thing after you last used it!) and…realize you don’t have the drivers installed on the computer you are using. After digging around on weird sites to find the particular not-latest-vintage driver version that works best on your OS (unless you’re running Linux, where they all just work!), you do the TX/RX/GND dance, then realize you’ve got TX/RX backwards, then realize that in fact you haven’t, it just wasn’t working before for some reason, but is now. Then you move back to your desk from your workbench and realize there’s no space for the board here and no way to power it, so…you juggle your laptop in your one hand back at the bench while trying to read the serial output that brought you here in the first place. At least that’s how you used to – hopefully now, you are not just older, but also have WiSer.

WiSer is a pair of open-source, wireless serial dongles, which aim to eliminate all of the hassles relayed above, and many more. For starters, there are no drivers required: just plug the WiSer-USB host into your USB-C port, and you are good to go on Windows, macOS, Linux, or even Android. The WiSer-TTL client can then be powered by USB-C, header pins, or castellated pins (if you pop the case off). From there, the pair act like a normal serial cable; an LED indicates their connection, and Tx/Rx activity is indicated by corresponding LEDs on each end throughout the session. To be more accurate though, they act like a normal serial cable, sans the cable itself – meaning your project can be sitting on your workbench, while you and your computer monitor it from your desk – an ESP32-S2-based Wi-Fi connection between them allows distances of up to 20 meters (line-of-site in ideal conditions) between your target.

To put the WiSer pair through their paces, I connected the host to my GPD Pocket 3, fired up PuTTY, and  connected the client to the ground and serial pins (GPIO 14 and 15) on a Raspberry Pi 400. The reason for selecting this target is that I’d not need to write custom firmware in order to test the serial functionality as with an Arduino or similar, and the fully-fledged computer would give me a lot more visibility in the case of any issues, rather than trying to figure out what was going on with a serial-monitoring solution…without having serial to debug it. I wrote a quick Python script to output “hello from WiSer” and then an incrementing integer value on the Pi serial, and then…nothing happened. Too many unknowns, probably – maybe my script is wrong, or I didn’t do all of the things required on a Pi 4 to enable serial communication? Maybe the dongles aren’t paired, even though the LEDs suggest a connection is being made? So I grabbed a PL2303-based cable and…wasted a ton of time trying to find drivers for Windows 11, with no luck. Then I grabbed an FT232RL-based cable, installed the drivers, and…got some garbled serial output. I restarted the script and Putty, per the old turning-it-off-and-on adage, and…it suddenly started working! Yay! So now that we know Putty, the script, the Pi’s serial port etc. are working, let’s swap our cable for…WiSer’s lack of cable! And it worked perfectly! I’m not even sure why it didn’t the first time – probably a mix-up with that old TX/RX dance or something not quite connected or initialized in the right order – but it immediately started working perfectly with no cables, and I started doing that magician’s-trick-style waving of arms to demonstrate to myself that there were no strings attached! I then began wandering around to see what the range was like, and managed a good 20-30ft line-of-sight before “hello from Wiser” started dropping sequential digits. Using something other than just RX/TX at 115200 baud 8-N-1 could probably have provided a better outcome there too, but this was sufficient for my initial shakedown.

WiSer is one of those tools that you never knew you needed, but can’t imagine living without once you have it. I’m already thinking of all of the exciting use cases it will enable, like monitoring sensor data from a wearable device using an Android phone (via USB-OTG and the UsbTerminal app)! Plus, ya know, just getting some quick serial output on a computer you’ve not already installed every USB-to-TTL driver known to humankind on! Magic!!

WiSer is currently crowdfunding on Crowd Supply.