 All right, this week's IonMPI, brought to you by Digikey and Adafruit, is from Epson. Yes. This one is right on time. I don't have a lot of clock and time jokes because it's a precision RTC set from Epson. These RTCs, you know, what's interesting is I don't think of Epson necessarily as making chips and RTCs, but they are really famous for their crystals. We use Epson crystals all the time in our devices, and so it makes sense that they take something, this is basically a 3.2 by 2.5 millimeter crystal, and they're like, we're already really good at the crystal part, let's shove an RTC chip in there, and they did. So we're gonna feature the RX 8901 CE, but there's also the 4901, which is the SPI version, and basically this is, you know, Epson's really good at crystals and temperature compensation for crystals. Now they've added a microcontroller, a silicon chip inside that acts as a real-time clock and is temperature compensated, which is really important because this is something that people ask us about all the time, is how can you have precision timekeeping. You know, I think I was even looking, you know, Jepler, who's one of our engineers, is like, I'm a time nerd. If you're a time nerd, you know it. You want to have the best, most accurate time possible. Turns out that's actually pretty hard to do. You know, a lot of people have used chips like this, temperature compensated RTCs from Maxim, and I do love these chips, but I do want to mention that this is basically, you know, another option, so if you aren't able to get these chips because they've been really strongly affected by the chip shortage, or you want to try, you know, another vendor or something that's a little more affordable, this chip is a really good option. So, you know, as I was kind of, you know, looking into this, I was like, well, why, you know, why is it so hard to do really accurate time? And I think one of the issues is that people have, they have not misinterpretations, but they have experiences with clocks and timers around them that influence how they think time works with electronics, and there's actually a lot of work behind the scenes to make time very accurate that you're like, you're not even aware of. So, you know, even, you know, historically, if you had an alarm clock or a wall clock, it plugs into the wall. It actually uses the 60 Hertz frequency of the mains in order to, you know, because it goes 60 Hertz here or 50 Hertz in Europe, and it uses that to power a timer, you know, a flip flop and a clock divider, and then that's how it gets 1 Hertz. And what's interesting is like, you know, the 60 Hertz is actually really good enough that you can have extremely accurate timekeeping, because that frequency is generated by, you know, the power plant in your town or outside your town, and they can synchronize it to make it like a perfect 60 Hertz. And, you know, if you look at this website, LeapSecond, they actually did analysis. So, during peak hours when there's a lot of power, actually the frequency kind of goes up and down a little bit, but at the end of the day when the power usage is lower, the power plant will actually adjust the frequency back. Like they'll kind of like give you some extra cycles or remove some cycles or kind of tweak the frequency so that on average, it really is like extremely precise 60 Hertz. Problem is, is that a lot of people don't plug into mains voltage anymore. Oftentimes, you're using a switching power supply or USB, and so you don't have access to this like pre-calibrated 60 Hertz signal that will give you like really accurate timekeeping. So, a couple options that people have used historically are, you know, a WWVB, this radio receiver kit. So, this is a radio transmitter that's, I think, in Colorado in the United States, maybe a couple other locations. And if you have, you know, this radio module, you can receive that signal and it'll give you extremely accurate time, because the transmitter is, you know, atomic clock accuracy. It's like, it is the NIST timekeeper. The problem is, is that, honestly, all the way on the East Coast here in New York, we never got this working really well. We just had a lot of difficulty, especially inside of an apartment. You really have to have the antenna either outside or, you know, pointing in the direction of Colorado or whatever in order to get good signal. Look, I bet if you're in Nebraska, you're gonna get amazing signal. We had a lot of trouble here in New York City. And of course, again, you can't have it be indoors. It has to be kind of outdoors-ish or near a window. Another way that people get accurate time is with GPS. GPS also gives you, you know, atomic clock precision. You have to face the sky with the antenna. But, you know, once you get signal from there, you get the absolute accurate time. But again, it's kind of expensive, uses a lot of power. You need to synchronize with these satellites. And then, you know, finally, if you have network capability, if you could use NTP, again, also, this is a atomic clock synchronized timekeeping service. But all of these things, you know, the 60 Hertz mains is inexpensive, but a lot of people don't connect to mains anymore. They're going to do a switching, through a switching power supply. But the radio, the GPS and NTP are all very power hungry. Like, you need to have internet, or you need to have a receiver or a radio. And so, while those are really good ways to keep your project synchronized really well, a lot of people want something that's standalone. And so, when you use something like a real-time clock, you're going to connect it to a crystal. And usually, it's a 32 kilohertz, 32.768 kilohertz crystal, which means that, you know, one out of, one to the, sorry, two to the 15th power times divider of the clock frequency 32.768 is one Hertz, and then that's your one second timer. And the circuitry that does a dividing is perfect, right? Like, it's very easy to make something that divides by 32.768, because again, it's a power of two. The problem is that the crystal itself has some variability. Even the highest quality crystals are going to have some variability of about 10 to 20 ppm, depending on the temperature, especially with temperature, but also just natural variability, because crystals aren't, you know, they don't oscillate perfectly on time. You know, atomic clocks do, but they're again, extremely expensive. So you get these crystals, they're 20 ppm, you do the math, 20 parts per million, ends up being, you know, you calculate there's 86 something, something thousand seconds per day and, you know, multiply that by the 20 over one million and basically turns out to be two seconds a day of plus or minus loss. And over a month that adds up to, you know, almost a minute. So it's like two seconds, you know, 2.8, 1.8 seconds a day, but it can also be a little bit more depending on aging and if the temperature gets very extreme. So basically, you know, you're losing up to a minute a day, a minute a month, and that can be quite a lot. It's a very annoying thing. It means you're constantly, you know, you have to synchronize your clock with, again, one of these atomic clocks, or you can go with a temperature compensated crystal oscillator with Epson has. And what that does is it'll be able to cut it down from, you know, maybe 20 ppm to like three or even, you know, two ppm, depending on if it's commercial versus industrial temperature range. It's a little bit more expensive. You're adding a dollar or two, but it's not as expensive as a GPS. It's not as, it's not very power hungry. The circuit is, you know, does little tweaks here and there to get the, the oscillation to be much closer to 32.768, or it'll add or remove pulses to, to even it out. So you basically end up getting closer to true 32 kilohertz signal. So this is the, you know, this is what we've got here. It's a temperature compensated crystal with a real time clock in it. There's two versions, I squared C SPI. There's also two pin options, pin A and pin B. I think one has frequency out. The other one has more event in inputs. But the interesting thing is the frequency tolerance, that's what you want to look at. So for the XS series, you get, you know, as little as plus or minus three ppm, which basically means plus or minus eight seconds. It's about, you know, one 10th, one, you know, one eighth of as much variation in frequency over minus 40C to 85C. And then for very hot temperatures, you know, it is going to be a little bit more than that. So above 85C, which again is, is very hot. It's not 85F, 85C plus or minus five. So this could be very good in hot environments where you want to get a better timing rate. And then there's an I squared C version, SPI version. There's also, you know, all the RTC stuff you'd expect. The calibrated, the temperature calibrated frequency output event input pin. So you can like timestamp stuff without having to wake up, separate battery and V out. Power supply can be, you know, 1.6 to 5.5 volts. So really nice wide range, wide temperature range, you know, auto switch from V out to V bat. Everything you want in your RTC and it's temperature compensated and the price is really good. Compared to many other temperature compensated RTCs, you know, it's a look kind of like half the price is quite, quite nice. Available on Digikey and it's in stock. Yes, that's the best part. There's a lot of them in stock, both the I squared C and the SPI version. And, you know, usually, sometimes the companies have, you know, little sales videos and stuff like this. This is a little different. Epson has a really beautiful video that goes along with this. This was so relaxing. I guess felt like so much better watching this video. This is really, really good. We rarely play, you know, just like, here's the sales and marketing video. It's actually really nice. Epson did a really good job. So we are going to play it. Maintainance is a work of art. In the end, it's a micro-onetime test. This is what's required of us. And that's the only thing we can do to gain experience. It takes years to get used to it. This is the artificial water-based principle used for water-based devices. Especially for sensors-related devices, artificial water-based devices are very high-quality materials. It's been three months. It's been six months since we started. I'm always excited to work with the manufacturer. The material is the source of the material, so when you make good material, it becomes the advantage of water-based devices. To make good water-based devices, you need raw material, solid water-based materials, mold, and people. You can't use anything. Water-based devices are alive. Isn't that cool? I promised I wouldn't cry during an Ion API, but... No, I was just so peaceful, this crystal so beautiful. I've been doing this biz with you for a while. I've never seen a video where they go through and show the process of growing crystals like this. I know. Actually, I didn't realize that they... I also thought they were mine. I, for some reason, I was like, I didn't think like, oh, yes, of course they'd be ground. You could grow them. But they're beautiful. I mean, they're enormous and they're perfectly clear. Yeah, I mean, it's like they grow them for three to six months. So it's like, you have to have perfect cleanliness. Everything has to be temperature. You know, everything has to be set up to make these gorgeous, perfect crystals every single time. And they've been doing this for like, I mean, probably 100 years. Yeah. Can we get a crystal growing machine around here? I kind of want one now. I mean, like, that thing is cool. Yeah. Can we get some of that government money to do a crystal fab? I don't know. They're beautiful. I mean, it's, I mean, it's, and it's cool how you can tell, like, if they get one big crystal on that, that turns into millions of little crystal oscillators that you guys use in your circuit. So a little bit of every microcontroller board that you've ever made. This is why we like doing IONMPI, because we learned something new every single time. I really didn't know how crystals were grown. I don't know. And that's this week's IONMPI.