 The great search brought to you by, for Digikey, every single week Ladea had used her powers of engineering to show you, yes you, how to find stuff on digikey.com, thanks Digikey. Ladea, what are you searching for this week? Did you know there's a part shortage? I did! I do, I do! Okay, well today is another adventure in part shortage land, so this week I'm looking for some alternatives to make, to use for the very popular MCP 23017 GPIO expander, it's a 16 pin GPIO expander over iSquared C, which I really like, I've been using it for like over a decade, but it's totally unavailable, we have some on order, not sure what I'm going to get them, again a lot of stuff from microchip placed orders a year ago and they've been pushed out, so let's go to the computer and I'll show what I would like to replace. Okay, so what's interesting is you can get the DIP version, but what I really want is this is a very popular breakout, which is great because it has 16 GPIO expansion, address, interrupt output, it's a very easy, low cost breakout that over iSquared C you can add 16 GPIOs, and here's the things that I like about the MCP 23017 and 23018, sorry 23008, but specifically the 017, 16 bits, so we IRQ, so you don't have to constantly pull it when a button is pressed, built in pull up resistors, which is big because there's the other GPIO expander that we stock, the AW9523, doesn't have built in pull up, so it's a little bit annoying, and I like that it runs on 3 volts or 5 volts, which is very handy because you can kind of use it a little bit as a level shifter, a teeny bit, you know, you can use it with 3 volts, but use it to power LEDs or send signals to 5 volts servos, so it's sorry not servos, people use it for rotary encoders, so I do like the MCP 23017, if I can get more I would just use that, unavailable, so let's find iSquared C, 3 or 5 volt power and logic, 16 GPIO iSquared C expander with interrupt output capability, and ideally a small package like this, so I can make a similar breakout board, maybe one that's even dropping pinout compatible that people can swap out while I wait for the 23017 to appear, okay so I did want to show, yeah, you know, there's no 23017, this is the chip I would normally purchase, and it's like, you know, 2023, maybe I'll get some in 2022, but I need them sooner than that, so let's go to IO expander, so I just went to the same topic because I'm like, I might as well be there, and then let's look for our standard, you know, you want active products, and I want 16 IO, although I might do a little bit more, because you know, well it's 20, it's probably still fine, I'm going to not select this like 8 output only input only, like I want them to be all GPIOs, okay, so I'm going to apply, next up the interface, I want iSquared C, you know, iSquared C sometimes has multiple names, it's called TWI, two-wire interface, two-wire serial, SM bus, it's all going to be the same, and then Voltage Supply, I'll pick that, I want to want the surface mount, that's important to me, it has to be easy for me to pick in place, and I do want Interrupt Outputs, and then the Voltage Supply, you know, I want, I don't remember how to select, sorry, Option Click to select all the ones, I want it to make sure it goes from 3 volts to 5 volts, so I'm going to pick these, and I'm going to skip this one, because I want it to also cover 3 volts, and let's see what we got, okay, so actually there's a lot of options and there's quite a few that are in stock, which is cool, so let's look at only ones that are in stock now, and there's a quite few from NXP, I've used NXP Expanders, they're great, Analog Maxim, also great, let's, I want to keep, get something that's within the price range, remember the MCP, 2317 was like $1.25 per, so I want to try to keep it at that range, so I like to view prices at $1,000, because the prices for one piece is always like, it doesn't really give you a good idea of how much it's going to cost, some chip companies like the cost of one is basically the same as the cost of the thousand, some you get pretty big discounts, so go to a thousand and then we'll see what's up, so there's a couple good options, the PCA 9535 is available, comes in a couple different packages, but the first one that came up was actually, looks pretty good, so this is the SX 1503, 16 channel, it's got 28 QFN, so I know it's about the same size, which is kind of nice, the pricing is really good, it's about 80 cents a piece, and then I looked up the data sheets, and you know, yeah they're like you can use this with 3 volt logic and controlling 5 volt LEDs, there's a reset pin as well as an interrupt pin, there's only one interrupt compared to the MCP 2317, but I think that's okay, lots of GPIO, they have versions with 8 channel, 4 channel, you know, you want to have more pins, less pins, and another thing that I wanted to check for is pull up capability, because that was like the thing that I really wanted, yeah so programmable, true bi-directional style IOs, so it means input and output, and programmable pull-ups and pull-downs, so and all 5.5 volt compatible IOs, this is actually a really good, really good option, it basically has even more capability than the MCP 2317, because it actually can do pull-downs as well, the MCP can only do pull-ups, and I'm willing to kind of look beyond the fact that there is only one IRQ, I think that's not a big deal, and then I don't know if there's address, okay yeah there's one address pin, so you can have two of them, not as many as the MCP, but again you know it's available, and I'm willing, oh wait so that's the, that's the 013, yeah so there's, oh I might not be able to change the address, hold on a second, because the 15, the SX-1503, see if I can find the pinout for that one, lock diagram, okay so this is the 4 channel, 8 channel, 16 channel, so it looks like there's GPIOs, and there's a reset, but there's no address, so this is a fixed address, so yeah that's that's the one downside, you only get one one address pin on 0x20 hex, but you know I think it still might be good enough for most people, if you don't need to chain multiples, and then maybe like this could be useful for people until I can get more of those MCP chips in, you know you need more GPIO expansion, I don't know, we'll get a Grand Central, well you can't get Grand Central because I can't get those chips either, and that's what it's like living in a chip shortage, but I'm still gonna make a breakout with this, I think it'll still be useful for 75-80% of people who don't need to chain multiple boards together, and we'll see it native food shop in a couple months, and that's this week's great search!