 The great search brought to you by digiki and a to fruit every single weekly day to use the power of engineering to help you You yes, you find things you that are hard to find because we're a little part shortage And a data. What is the great search this week? Okay this week? I'm actually Working more on the feather wing that I started last week last week The great search was on finding an rs 232 Transceiver chip that would take TTL logic at three volts and convert to plus or minus six volt logic And so we sourced apart the max three two three two I think it's wonderful. It's available in a couple different packages. It's in stock So check out last week's great search if you're curious And then this week so as I was working on this I was like, you know one of the things that We've had requests for not just an rs 232 wing which I'm designing But it's also remind me of an rs 485 wing so rs 232 is TTL serial, but with very wide voltage range. So instead of having Zero to three volts. It's like plus or minus six volts So it solves the problem of like how to get this signal very far by just making the voltage four times larger Which is like a totally valid way of doing it and for rs 485 Also known sometimes as DMX does it a little differently Instead of just making the voltage swing higher. It does a differential signal. It's a little bit like canvas So, you know for rs 45 is used for industrial purposes again. It's also used for DMX it's like a multi tap system. It's like it's uses TTL, but it's a little bit more going on and I Thought you know, let's go to the computer because I'm just new computer stuff I thought that I had so much room, you know here because it's this is ignored this Adelagher some Adelagher I just I just recycled the Adelagher layout, you know I was gonna have the RS sorry that the DE 9 over here on the edge, you know, have this hand soldered But you know that way it fits nicely and then a terminal block over here with RX TX and ground But I have a lot of space left over and so I thought like oh I can make this be like a combo because You know a lot of times if you're using RS 232, you know, you're often also interested in RS 485 because you're just like how can I have this long distance serial transmission and So what's interesting is I actually Shoot I Want to look up the 45 yeah So so if you went for like RS 45, I actually saw this design From teeny sign and I'm like oh, this is kind of what I want. It has you know, you can select RS 45 or RS 232 And then there is you know, this SP 232 X or something here and then there is the Adapter chip here. This is a max 461 and then you can see that it's like you can have one or the other and I thought like that would be pretty Handy, you know, you'd have a switch to enable or disable either chip Maybe disconnect it completely And also, you know, if it can't necessarily use both at the same time, although, you know, just because of the voltage I don't want to necessarily mess up The the voltage outputs What I could do is, you know, only pick and place the parts for one or the other that could also be a design Because it would be like so similar and again, I have that space I might as well maybe make a design that can do either or both So this is kind of interesting and inspiring but what I need is to get a transceiver now The thing is I've never actually used RS 45. So I'm gonna have to pick up something that I can use as a Like the other side, I'll have to pick up some DMX light or something Whereas I showed you last week the the space ball has RS 232 RS 232 is like kind of everywhere That's very easy to get RS 45, I don't have anything but it's a common request and so I think it's a worthwhile thing for me to add on so RS 45, you know, there's a Wikipedia article and it's it's basically a you know instead of Instead of a you know single, you know one for you RX one for TX is there's bidirectional Sorry differential lines that go up and down and that's how they they, you know They also have idle where they're both sitting at zero volts. There's no There's like negative positive and zero and so you can actually have the bus be shared and then for DMX I have to make sure that it's more than 250 Kilobit per second, but it looks like it can go up to 10 megabit per second So what I want to dig a key So the good news is that if you like search for RS 45 There's a ton of converters and adapters and there's also the transceivers So to start with one thing that was interesting actually is there is Some chips that are both RS 232 and RS 45 They tended to be more expensive So if I plot, you know, I did look and I was like, oh, that's interesting that there's combo chips Like somebody else had the same idea of like oh like why have one and you can have two The problem is that the chips like, you know, they look amazing this max 31 60 it's super awesome, but it's 12 bucks a piece and While I'm sure it's absolutely worth every penny it would be kind of I'm like, I think I have enough room I think let's just have two chips and Let's do it that way. So I ended up not You know, I ended up not wanting a multi protocol, I'm just going to select RS 45 and then There's isolated well, let's first pick active only because I only care about chips that are currently available And then there's driver receiver and transceiver, which I don't really know the difference But what I do care about is how many drivers receivers and I want I don't want to have just receivers I just want transmitters. I want transceivers. So we'll get the one one and two two So it's like either once, you know, RX and TX or Two TX to RX like we showed with the last week. We had a two two RS 232 transceiver Um, so there's isolated ones Again, I'll show that I did look at these real briefly and and these are cool They're all out of stock and they're a little bit more expensive But I did think it was you know, it's something to look into if we can eventually get them in stock. They're they're a little bit bigger They're 16 SOIC and they're also completely unavailable like most chips But there could be some purpose for a an isolated RS 45 so I was like, okay, that's interesting, you know, I'll keep that in mind So looking at just the RS 485 non-isolated transceivers We also only want surface mount parts because I'm not going to solder through hole For the data rate, I do have to make sure that it does 250 Kilobot or above looks like it goes to like almost infinite Basically, I just don't want the ones that are guaranteed to be slow just wasn't that many And there's still a lot of options So I'm going to go for only ones that are normally in stock and in stock like ones that are stocking and available And that gets me down to You know, I think a couple hundred options And then it looks like, you know, a common there's like a jelly bean Part layout, that's an eight SOIC it kind of I looked around at some other RS 485 transceiver chips like setups and breakouts And they don't seem to use like these eight SOIC because it tends to be just like one on X and one TX So While I may change my mind later, I'm going to kind of go with this standard eight SOIC package, I'm gonna select that and The reason being that, you know, these transceivers like can transceivers it looks like There's a lot of makers and they're all kind of the same and it's a very generic part Which is good because it means that if it's out of stock one, you know from one supplier I can switch over to the other so I kind of want to stick to this kind of standard Layout the next thing is whether I want it to be half or full duplex And to be honest, I'm actually not sure but I think I want full duplex because I want it to automatically transmit and receive Although I have to look into that because again, I'm like as I'm looking into this is like, oh, there's all these little like It's like it's so simple, but there's all these little details. But for now, I'm just picking Full duplex And another thing is for voltage supply While I could have a little boost converter, it would be cool if I could get it working off of 3.3 volts because Um that way I wouldn't have to add an additional, you know boost converter And um this part kind of came up first so it has the most in stock And the price is pretty inexpensive It's one of the least less expensive ones And I'm always into like anything that has over 10 000 pieces in stock is kind of like a good sign for me because it's like Oh, this is like a standard stocking part A lot of people use it so you have to have a lot of them in stock um So I'm going to start with the isl 83 40 um 490 And this part Uh, I can open up the data sheet Um, it's a 3.3 volt supply, but it's five volt tolerant um And it can go up to 10 megabits. So it's high Data rate it was designed in 2018. So it's kind of got a more, you know, it's more modern There's a couple that are older, but that's a fairly modern date For something like this and it looks like they have a couple variations. So they have versions that are slew rate limited Uh that have low power shutdown or that are looks like you basically can either have Full duplex or low power shutdown. You can't have both which makes sense It's like if you're full duplex it means that you're kind of waiting for signal You're gonna you can't really go into low power mode because you're you're waiting and listening Whereas on half duplex you could tell the chip. Hey, you know, there's I'm not waiting for message So let go into power down and I'll tell you when to listen for um Getting an idle. So it looks like there's a couple options there For this chip, but they're all um You know, they're they're all this kind of standard, uh So I see this is the half duplex and this is the full duplex version so I don't know. Uh looks pretty good. Um, I basically have to look into Um, again, whether I want to get this Um, you know, what's more important to be basically having a half duplex low power controllable Or full duplex It you know kind of does its own thing. Um, but Um, you know, you don't have to switch between one or the other I don't know which wiring set up people tend to use more. So I'll look into that and um, Hopefully I'll I'll pick which sub variant But this family looks really good. And of course, I love intersail and um, we're in a south's they're a great chip maker So I'm feeling pretty confident with my decision. So I'll um, I'll get some samples I'll start working this into the design and then when I do a prototype I'll pick up a dmx light or something and I'll try to just get it working or I'll just build two and I'll try to get signals Uh transmitting back and forth That's a great church