Since the last episode, we have put a couple of hundred boards through the soldering robot during commissioning. The PiicoDev RFID module is also nearing completion. In this episode, we will show you what we have learned on the soldering robot and I will show you some cool stuff that you can do with NFC.

The soldering robot works just like how you or I would solder a through-hole part. It has a hot iron and a feed of solder. It places the iron on the pad that you want to solder and feeds that solder wire into it. There is an X gantry that moves the iron left to right, a Y gantry that moves the table forward and back, and a Z to drop the iron down to each pad.

We thought a great hello world project for this machine would be soldering headers onto Raspberry Pi Picos. Up until now, we have been hand soldering the Raspberry Pi Picos with headers. If you have received one from Core Electronics, then those Picos have been hand assembled by either Bryce or Liam that work right here.

The working area of the robot is a table with four corner mounts. We have created a laser cut fixture plate that keys onto that table. of having too much acceleration.

There's a chamfered corner on the fixture plate that is keyed so that it can only go in one orientation. This allows for a 24mm grid of M3 holes to be scattered on the plate. This grid provides a higher resolution than the coarse grid on the plate, as long as the pitch of the finer grid is a factor of the 24mm. This gives the user more freedom when mounting the jig. Once the jig is in place, soldering can begin. The machine has tunable profiles for each type of pad that can be programmed. This includes preheat time, how much solder to feed at a moment, and how fast to feed it. An early attempt at soldering may result in poor wetting and even a crash of the tip into the pin. This is an outcome of having too much acceleration. After tuning the machine, much nicer results can be achieved.

Having just regular soldering pads can be difficult to program into a machine. To increase reliability, we found oval pads to be more successful. These pads are similar to those found in old Dick Smith electronics kits. The 3D printed jigging we used was a thermoplastic, which raised some suspicion. However, it performed well and the first four units were printed in PLA. The last one was printed in polycarbonate, which did much better due to its higher glass transition temperature. We will continue to use the 3D printed jigging and see how it goes.

Leaps and bounds with the soldering robot! We last talked about the PiicoDev RFID reader, which is now in a hardware lockdown. The hardware and libraries are done, so expect to see it coming out soon. We discussed the iterative design process to tune the antenna and matching circuit, and demonstrated it on Arduino. Now, we have our own library and can show what it can do.

Most people will just want to hold the RFID tag over the reader and get the ID for access control or vending machine projects. However, more adventurous users may want to dig into the user memory space of the tag. This has more than just an ID, and can store images, strings, and even URIs like URLs, telephone numbers, and Wi-Fi SSIDs.

Here's a quick demo. We have a very basic example where we're programming the Chrome Electronics website URI onto the tag. We run the script, hold the tag over the reader, and the URL is written to the tag. We can then get out our phone, hold it over the tag, and the Chrome Electronics website will open.

The tag to the back of the phone opens the Core Electronics website. I've only tested this with websites, so URLs like HTTP, HTTPS, telephone numbers, email addresses can be set up to create a new mail to a specific recipient. This is the Wikipedia page for a list of URI schemes and there are many options. FaceTime links, opening a file on a remote directory, and even coordinates can be put in. To test this, I used Google Maps and Core Electronics. I grabbed the latitude and longitude, put it into Thonny, and ran the program. When I touched the tag to the back of the phone, it pulled out the coordinates and there we were at Core Electronics. URI is pretty intuitive to get started with. You just put in the scheme tag at the front and the data you want to put in at the back.

Getting this together to work on Raspberry Pi Pico, Raspberry Pi, and Micro:Bit all with the same user code did have its challenges. Usually in PicoDev, we have just one device module, but because this was a lot of code, it wouldn't fit on a Microbit. We decided to split the functionality so that Raspberry Pi and Raspberry Pi Pico get the full function. They can read IDs, numbers, strings, and URIs. For the Micro:Bit, we split it in two so that it would only be able to read the unique ID.

This project has been my first brush up against using URIs. I'd used NFC tags to follow links before, but hadn't really explored the inner workings. In our device driver, it looks pretty familiar. We have the class, we have the PiicoDev RFID, all the definitions for all the functionality within, but then right at the bottom, there's another import command. We check that we're not running on a Microbit. So if we're running on a Raspberry Pi or a Pico, we call another import statement. And this imports into this class, the expanded set of features. We have another file, the RFID expansion, which is right here. And we import all the additional features that are required to say, write URIs to the tag. This also means that this expansion file is purely optional. No matter what platform you're running, if the expansion file is included, it will be imported if appropriate. And if it's not included, that just means that you're running with the minimum feature set, which is just to read tags, unique identifiers.

Here's the kind of range that we can get out of this thing. I'll just bring the tag just to the edge of the range. And that's about 25 millimeters, which is pretty impressive given the size of this coil. You know, we got about 25 millimetres out of one of these generic modules, which has a coil area that's about four times. So I'd say that's a win. NFC tags, very versatile by the look of things. It seems like with URI, you can do some really, really powerful stuff. So looking forward to see what you can do with one of these.

That's probably what most people using Micro:Bit are going to be most interested in anyway. If you want to see anything a little bit closer, or if you just have some questions about this content, let us know on the Core Electronics forums. Until then, that's all I have for you today.

Thanks for watching! Next time, we'll have even more exciting content.