 The Great Search brought you by Digi-Key and Ada Frint. Thank you Digi-Key, every single legal editor is a power of engineering. I hope you guess you find the things you want on digikey.com. Lady Ada, what are you looking for this week? Good question. So I just covered on the desk of Lady Ada that I am revising many display things that were, did not really make it through the chip shortage and have to have serious revisions done to them because so many parts changed. Backlight drivers and connectors and TFTs and touchscreen controllers and more and more. So this 2.4, I agree, this 2.4 TFT feather wing has been revised and since I revised the feather wing version, like you can plug in various feathers, I wanted to also update the Raspberry Pi version of like the same thing. So this, let's go to the computer, I'll show off this hat. So hats are hardware attached to top for Raspberry Pis and I did also put off a lot of these because the Raspberry Pi were not available for like a year or ish. I mean you could get them but it was like very challenging and so you know in my gigantic parallel revisions, I hit 450 revisions last night out of 600 ish boards that we manufacture right now. The Raspberry Pi once kind of got put on the kind of the end of the list because I was like, well, I'm going to wait till Raspberry Pi is available again anyways. So this also needs to be revised. A lot of different pieces and parts are not available. The resistive touch controller and the TFT were hard to get but now that they're back to getting it back to manufacture, another part that actually got discontinued as a specific EEPROM vendor that I use for these EEPROMs is unavailable. So I thought I would also do a quick change over to use a different vendor for these, I would say, you know, jelly bean components. This is the EEPROM. So Raspberry Pi, you know, and there's more Raspberry Pies are available now so people can start making Raspberry Pi accessories and one of the standards for hats is not only the shape but okay so this Raspberry Pi official article which is like nine years old by the way from 2014 talks about the standards of hats and not only does it dictate, you know, the pinouts and the physical shape with all the slots but down here, sorry, skip it, okay, they talk about this EEPROM that is on board. So there's two special iSquared C pins on the hat pinout that are not used for like user iSquared C there for hat identification and if you attach a generic iSquared C EEPROM to it and there's a little tool that helps you format the data that goes into the EEPROM so that the Raspberry Pi software can identify it, the idea is that you would be able to put a hat on like a display or like the sense hats or like activity hat or whatever or like the Lego hat that they made and it would automatically know like oh i saw that you attached a display hat let me load up the device tree kernel overlay and any other software and install it and get it ready so it's like almost as plug as play as USB on like a Mac or Windows computer where you plug in your mouse and it just magically works or you plug in your monitor and it just magically works the idea would be the same thing but with hardware um so um let's go back here so um this EEPROM here and I think you know yeah it's a 3G you can barely see bits is 24C32 these are generic iSquared C EEPROMs and 99% of the time they come in this 8SOIC format the 24LC or C series is what they usually start with or sometimes it's cat 32 so there's there's 24 in there and then 32 for 32 kilobit which is 8 kilobytes um somewhere in the name but there's sometimes like a C or an L or a cat or an ST and I'll show you that when we search for it they're all basically generic and identical sometimes they have extra capabilities but you can pretty much use anyone you want and they all respond to iSquared C address 50 and then they have three address pins they can go from 50 to um oh x uh f 5 7 right because of three addresses um so let's uh go to digikey and I'll show you search for these oh so we in a previous great search tool for 25Q series chips so you're like oh why can't they just use like the you know 25 GD25Q or W25Q the 25 is the SPI version of the NOR flash it's different than EEPROM so watch out and there's a little 23 series um 23LC and I believe 23LC is SRAM yeah so let me just verify yeah it's SRAM SRAM does not it's volatile when you write data it doesn't stick around after reboot so it's great for um when we you when we need like a big memory buffer for say um e-ink displays we use it as like a back buffer for the e-ink because we don't care how fast it is e-ink is very slow uh but we do need a lot of memory to buffer the entire display and we might want to do it off the microcontroller if you don't have PSRAM 25 series is not EEPROM it's flash you need to erase and basically write a whole page at the same time um so it's good for large storage it's not good for small amounts of storage EEPROM which is the 24 series is great for small amounts of data yeah I don't think you can store more than a couple kilobytes the SPI NOR flash gets easily up to like 16 um megabytes I think they probably even make more but it's good for like the megabyte range EEPROM good for the kilobyte range and non-volatile and you can erase and write one byte at a time which is quite nice uh actually it's just good for and it's also I squared C and these are used often there's used for like FPGA configurations um MAC address data for uh laura and ethernet devices um non-secure configuration remember you can read and write from them clearly they're played in clear text not good for security key storage okay not that's not what they're good for they're good for calibration data um serial numbers where you don't care if they get changed but it's good for like you know identification and again like MAC addresses and stuff or um you know if you want to identify the board that's common common EDIDs for monitors are stored on the EEPROM so let's look at memory so let's look only at active I search for I squared C EEPROM so we're only going to get you know what we're looking for there um we I think we've covered FRAM on INMPI before that is more expensive but it's instantaneous right and it doesn't get affected by x-rays or whatever like particles in space and so if you're sending stuff up in space FRAM is a good idea we're not doing that also SRAM is volatile so we don't want SRAM we want EEPROM only and we want surface mount because we're going to put this on a surface mount board like this and there's a lot of options and then remember we're going to look for uh 32 kilobits don't forget a lot of these memories it's I even get confused all the time they are defined in kilobits um and then if you want to know how many kilobytes you've divided by eight four kilobytes 32 kilobits let's do it okay so that really pairs it down um you will pay more for more kilobits so just pick the number one thing to watch for you can sometimes go up one sizing so if like you need you know if you're specced for one kilobit sorry one kilobyte you may be able to swap in a four kilobyte version all the pins are they're all pin compatible but the i-squared c commands to address the memory are not compatible for the smaller memories you can you literally will use only one byte of address if it's under like 256 bytes of data and then you know up to 64 kilobytes you would use two address and then beyond that you'd use three address bytes and so it's not necessarily you know smaller to larger just make sure you don't pass over that number of address bits read boundary because your code will no longer work you can't just put in a huge chip and think it'll work in something that's expecting a one or two address byte command to get data or a data okay so uh i think this looks good for voltage supply in this case for the raspberry pi it's 3.3 volt logic so i just want to avoid you know everything that requires 4.5 volts i don't think it's that many to be honest and then uh 220 options again these are jelly bean parts every chip company pretty much makes an i-squared c e-prom let's just look for in stock and not marketplace so that gets us one half down okay so you'll notice that there's a lot of different packages uh for this um so these e-prom's are not that big and so you can get them in a lot of package sizes that you know official if standard is s o i c uh so you know again sometimes you don't start with just 24 they have cat sometimes it's c sometimes it's lc for like low power but you'll always see that 24 in there and you'll always see for 32 kilobits 32 64 kilobits 64 8 kilobits 08 etc etc um they do come in like dfn sizes one interesting thing is if you are using this in a tightly packed you know you're it's a small package um sorry a small layout you don't want to like have this huge chunk in s o i c chip digging up a lot of room you can get the chips in sot 235 as well uh for sot 235 i will say um one thing to just watch out for it's not a huge deal um but this is a standard s o i c and t south package the sot 23 drops the address pins there's three address pins missing and so that it will you'd think oh okay so it only responds to address o x 50 actually it will respond to all addresses that it could have been set to if it had address pins so you will see both o x 50 51 52 52 up to 57 um i scored c um because it was meant it's meant to like oh you know whatever configuration so if you have nothing else on the i scored c bus that could conflict like in the version of this hat totally fine to use the sot 23 smaller not less expensive usually it's a little bit more expensive um if using s a s o i c you just set the address pins and then you can have a unique um address selection uh do know that they do have internal pull-ups sometimes or pull-downs so just watch out for that you want to connect them don't leave them floating uh and then you know sometimes these have other stuff like they have uh you know serial numbers or uh you know white protection areas but for like general purpose stuff like saving and reading data you don't really have to what you're probably not using some of this the special things that each each manufacturer adds in to like spike you know it's like oh this is my recipe for chocolate chip cookies like i and kuman you know they all have something a little bit unique uh to make it tangy but for generic purposes it doesn't really matter um so you know they even come in if you want tiny packages you can get it in this like you know 2 millimeter probably by 2 millimeter size package 1.4 by 1.7 so tiny little ee prom but you'll see it still has the 24 and 32 in the c in there this one has a g for some reason in this anyways um searching by uh price let's actually go let's go specifically say we want s o i c because i really just do want and watch out there's also narrow and wide s o i c in this case the part that i'm replacing is narrow so let me get the uh the narrower medium with you also get uh 74 tiny sot series um yeah a lot of good options so i think what did i pick in the end i don't know they're all good i think you know this one is fine this uh m 24 c 32 from s t you know it's about like 20 cents in quantity sounds reasonable i squared c up to 1 mega hertz wide voltage supply range uh and you know good everyday four kilobyte kilobyte i squared c e prom so i'm gonna pick some of these up and i'll get those pie hats back into manufacturer that's a great search