 The Great Search brought to you by Digikey. Thanks Digikey. And Advert. Bleeding it uses the power of engineering, smarts, and more, to Digikey's site to find something you might need, you might need. Yes. Someone might need. What is this week's? Great Search. Okay, so let's go to the computer. All right, not surprisingly this week's Great Search is about a product that is not available. The part you can't get and how are you going to find a replacement? So for a lot of boards that we've made, you know, boards with AVR chips, boards with expressive chips, they do not have native USB. They have native UART, and the UART is how you program them, and the UART is how you debug them, and how you can send data to a computer and such. Again, we love native USB, but a lot of chips still don't have them. Lower cost chips particularly don't have a USB core attached. And so you'll see on a board like this, this is the main processor chip at Mega328, our very favorite. And then over here, this chip, as you can see, this is a USB port, this chip converts the USB from here to UART to communicate with the microcontroller there. So two separate chips. We've been using USB to UART chips for easily 20 years. I mean, I think we started with the FT232BL, which we actually put some in the store recently, because we found half a reel. And they are pretty much an essential part. Now, you can use a microcontroller and program it to become a USB to UART converter, but we really just set up prefer to use an off-the-shelf one. We find that they can handle bot rates much better. They often have modem control pans. They can light up LEDs. They can have, you know, a lot more capabilities. And I think they're a lot more reliable and well-gained. I've liked them a little bit more. So that said, the chip that we've used a lot recently is the CP2104 from SILabs. A lovely USB to UART chip, inexpensive, easy to use, doesn't require crystal, doesn't require a lot of components, very plug and play and works up to like two or three megabots, really fast, good, especially if you have ESP32 chips because they are very large chips. And if you want to program them, you want to push that data out as quickly as possible. So, lovely, it's a CP2104. So I was like, oh, you know, let's buy some more CP2104s. And then I'm like, let's go over here. And then like, OK, let's, OK, they're not in stock, but maybe I can back order them. And it now says not recommended for new design. NRND, that's what NRND, yeah, I know, NRND. It's not end of line, but it's kind of the like, you know, the best by date is approaching quickly, right? This is, they're still available. You can still buy them, but not recommended for new designs. You can still maintain old designs, but please don't design this in. We can't really stop you, but you're going to be sad because this is going to be discontinued shortly. Why does this happen? Even for chip as popular as this, I think it's actually because they really do want to push people towards maybe a cheaper process. Or there's a little bit of bugs or improvements that they want to make. And they kind of wanted to shift you over. Again, that's how you can get this, but not recommended for new designs. So the question is, what do we do instead? So let's look at, you know, if we're going to, you know, and of course I contacted, you know, Silabs was like, oh, do you have a drop in replacement? And they said, no, we don't. We have this other chip. It's not a drop in. It's very similar. But I was like, well, you know, I might as well look to see if there's any other chips just in case I'm kind of missing out and see what the market is because there's a couple of different companies that make USB to UR chips. So let's go to interface controllers. And because of course we're doing a new design, we want only active stuff, not NRND. And we want a particular function. The function we want is a bridge that is USB to UR. Note that there are like USB to Ethernet, USB to FIFO, USB to I2C, USB to SPI, but we want in particular USB to UR. And let's apply all. Now, you know, we're doing a design spec. And so I don't really care if it's in stock right now. What I care about is like, can I get it in general? Is it normally stocked? It's available. So there's a couple of things. So there are some chips that are available right now. You know, the FT2321, 231, this is from FTDI, classic maker of USB to serial converters. However, you know, I'm kind of interested most in pricing. And so I'm going to say, you know, at 500 quantity, it's about how many a byte of time. What's my, what's a good bet for pricing? Price and put on does not, maybe because reels are bigger. So let me do 1000. Weird, the sort by price is not quite sorting by price. That's a new one. Let me get rid of the quantity pricing. This is exciting. OK, so I'm still not working. I don't know why. OK. So the there's Cypress and they make the Cy7C series of converters. I use them. There are, you know, about four dollars a piece. There's also the, like I mentioned, the FT230, also about two dollars a piece. The replacement that Sylab recommends is actually one of the ones that's up here. And it's $1.50. So if you're if you're going for price and it's close enough, there is the CP2102. Now, one thing to watch for the CP2102 is this is unusual. I've never really seen it before, but it's a chip that's available in three packages, but they're all with the same name. So they're all QFNs, but there's a 20 QFN, a 24 QFN and a 28 QFN. So one thing to watch for is, you know, usually I'm like, oh, just use like, you know, the first chunk of the name and then the package, you know, in QFN or T-SOP, and I'll tell you, you actually need to have the full part number because this one is the QFN 20, this one is the QFN 24, and this is the QFN 28. So looking at the 24, let's show you the thing because I went through this data sheet and we'll find the interesting part. So the good news is like it can go really fast, three megabod, which is nice. There are different GPIO functions for each package. And it was this cute. Oh, sorry. It's at the very top. OK. So there's the 28, 24 and 20. And each one has slightly different functionalities. They're all lead free. Yay. The 20 is the simplest. It doesn't have charger battery detect. It doesn't have VIO and VDD pins, which means you can't have it like 1.8 power. It's I think whatever, you know, VDD IO 3.3 volts and you can't have to stick with that. The 24 adds the VIO and VDD pins and the 28 adds battery charging detection. It has more GPIOs. The battery charge detection is kind of interesting. I, you know, it's kind of I think for if you have something where you want to like determine if you have enough power availability, like it can output to tell you like, yes, you can you can draw that much power from the charger from the USB port to charge your battery. The QFN 24 is the one that is closest to the CP 2104 in pinout. It is like 95 percent the same. It is not 100 percent the same. The difference is there's no VPP pin. So usually on the CP 2104, there's a programming pin that you have to put a 10 micro farad capacitor on. You don't need to do that. And the other part that is most important is there is now this requirement for a V bus divider. This is like a detection circuit to tell it when V bus is connected. Historically, you would wire this up directly to the V bus pin. You know, they've changed the design. You now have to use a resistor divider. So it's not dropping compatible. It's it's a little sad because, you know, I also feel like if it had been like one resistor was needed, you know, you could have like used that VPP capacitor and maybe like rerouted that package, you know, instead of a capacitor would have been a resistor and you can route it. But for whatever reason, they've they've changed it so that you you definitely need to have this resistor divider. So in my breakouts, sorry, USB serial, you know, so I designed another thing to note is there's the CP20102 and the CP20102N also different. You want the N variety. So the good news is that, you know, it's not too bad of a difference. It's not too different than than the CP20104. You know, I've in this design, I've added these two resistors that VBUS detect over here and you can see in the previous design, this isn't where the the VPP capacitor was like this is kind of an empty space. I deleted that and sort of shoved these wires down to make room for these two resistors. So that said, you know, it's I wish it was drop in replacement. It's not, but they're going to have it in stock, you know, in a month. It's about the same price as the CP20104. You do have to do a slight re-spin, but all in all, it's not a bad re-spin. And so like, you know, you'll have to pay for another stencil and another program if you're if you're doing your assembly. But I'm pretty confident that functionally, you're going to have the same, you know, functionality and support that you had in the CP20104, whereas jumping to a different USB serial converter. I'll say each one of them has its own little quirks. The side labs ones are a little different quirks than the FTDI ones, which have different quirks in the side press. So I'm probably just going to move to this, you know, version. And I do like the QFN package. I know there's other USB serial converters that come in like T-SOP, but this is so nice and compact and it's so reliable. I really like that you can go at high bot rates and it's consistent. I like the LED drivers and it doesn't do weird things when you plug it in. Sometimes other chips, you know, like pins start tobbling kind of funky when you plug it in, but this one is very reliable. So I like it. So I'm going to have to re-spin about 10 different boards from the CP21 to the CP20102. It's what it is. We're living in this land, but when they come in back into Stockholm, we'll order some samples and get those boards designed. So that's a great search. Hopefully helpful for others lacking the CP20104s in this silicon shortage life we have.