Good morning, all so, what's my next project? Well, it's to build something: a bit like a pro mini um to use in conjunction with my chili, pepper, usb to serial converter or the chorizo one. I might have to update that because the part ch340g is out of stock, but anyway today i want to focus on the pro mini. So what's on a pro mini, let's have a closer look. So what we have is the microcontroller with resonator or crystal reset switch with 10k pull-up resistor and differentiator capacitor coming from the dtr or reset trigger line.

We've got a regulator capacitors on input and output. We've got an led there for the d13, generally called l or built-in led we've got a raw pin which comes into the regulator, but that seems to go through the poly fuse and diode into the regulator. There's another led there, which i believe is just simply an on led um, there's a capacitor. I think this one's across vcc this one's on the a ref, i believe so capacitor 100 end to ground and i think that's pretty much it so i'll.

Just do a little sketch on a piece of paper so that i don't forget anything. So let's draw the micro as a diamond, because that's how it's laid out on there. That will remind me that's what it is. Um we've got some gnds and we got some vccs.

We need a resonator or crystal uh rares or t a l that goes on to two pins uh, possibly also a ground on there. If it's a resonator, we've also got the regulator we'll put that over here. Within out capacitors, like so to ground, that will go to vcc uh like so, but there's also the raw pin, which can go through a poly fuse also goes through the diode and that also links to vcc. What else we've got this? We've got this um, a ref which is simply capacitor to ground uh.

Anything else. That's essential, uh, the reset circuitry. Let's draw that so i've drawn that here, 100n coming in from well. Some boards call it dtr some boards have it marked green or colors of a particular cable uh, but we'll just call it dtr100n 10k to vcc a switch down to ground, which we want on the board so that we can manually reset it uh.

Anything else. Yes, led here, uh resistor to ground. I have some flashes of light coming out there and we want a d13 d13 led again resistor to ground flashes of light coming out of there. I think that's pretty much everything on a pro mini now, of course, i'm not going to call this an arduino board, i'm going to call it a giuliano board so that we don't have any confusion that it's uh arduino compatibil, although it will be um and i'm Probably going to go for a square form factor to give more space around the microcontroller, because this is my first microcontroller board and i'll probably get it made in black now square and black.

It's going to look a bit like an after eight and after dinner, mint. So i'm gon na call mine the giuliano pro minty. So let's get on to easy, eda and start the schematic for my pro minty. So i'm in easy, eda i've gone to the library, easy eda, search engine and jlc pcb assembled parts, and here there's a 18 mega 328p.

I did a search for 18 mega and we've got a tqfp 32 pin basic part which i'm going to place because that's going to be the micro controller on my pro minty so place that and that's the first item on my schematic. Let's start hooking up grounds. Vccs and as much stuff as i can prior to bringing in any more other components, so here are my basic ground and vcc hookups. Now we need a capacitor, so i'm just going to go to the simple library pick a capacitor c0603us and the capacitor is here for a ref to ground and it's a 0.1.

Yes, so that's correct so i'll, just wire that up from a ref to ground. Okay, that fixes that now, let's have a look at the crystal or resonator well in jlcpcb.com parts in the section ceramic resonators, which is under crystals, i found this, which is a 16 megahertz, 15 picofarad, i presume that's built in smd 3213. So is that 3.2 millimeters by 1.33 pin ceramic resonator. I think that'll do i'll make a note of the oh there's a copy button.

There. That's handy i'll copy that and see. If i can find that in the library and in the library there it is uh the cstc thingie bob 16 in the middle there, it's an extended part, but i'm not worrying too much about basic and extended parts now because um well, the one-off cost for using Extended parts dropped at some point from six dollars to three dollars, so i'm not too worried about it. Now, let's place that and uh stick it in my.

Oh! No, that's not right! I want to place the resonator so i'll, just wire that up the center pin goes to ground the top pin uh will go to or click it there. I think no, i want to click it there and take it into pin seven, which is marked extol and this one. If i it won't, do it, let's click it there and take it into pin eight. So that should work as my oscillator.

We need a d13 light emitting diode, so let's pick one out of here just pick a red for now. If i want to change it i'll do that later, so that comes from pin 17, which is pb5, that's d13 i'll put that there also need a resistor for that. So i'll get an r603 rotate that one and stick it there. So that's the d13 led or the blink led.

It won't do that with it. So let's click it like that and i'll put a little link in there oops. You need to do that and another ground which i'll attach there. Let's delete that node.

Okay. So that's the uh blinky led, that's done. I've got this wrong. Haven't i raw comes in through the polyfuse and the diode doesn't go directly to vcc.

Of course it goes to the input of the five volt regulator. Well, it's a day or two later, and this thing has morphed, as these things often do into a bespoke baseboard for these peripherals. So that's what i'm going to do and as such, i don't need any of the raw or regulator stuff that can all come out. I will keep a power led, but let's go back to easy, eda and see where we are on the schematic.

So this is where i'm at now, microcontroller resonator power led green and uh decoupling capacitor. On the reset side, i've got rst now that comes in from the usb to serial board through the differentiated capacitor 10k pull up, and that goes into the reset pin. So rst comes from my usb connector here, which goes to the usb serial converter that needs rst, but reset, of course, has to go to the isp header so that the programmer can program this chip with the bootloader, so that needs this reset signal. On pin 5 of the isp two more connectors on the baseboard will be for my display peripheral board and my radio tower board.

I wanted a d13 led. I've put a little link in there, so it can be disabled. I wanted a d2 sorry, d3 led. So i've done a blue one, a link again so that can be disconnected and i think that's about it.

The only other thing is that d2 i've attached to the end of this radio tower connector the radio tower only uses pins one to five d2 here is on pin 8 simply so that i can put my touch switch into there so that i can control the Relay on the uh transmitter, so that's it it's going to be on a green baseboard. I've decided this now won't be the pro minty, because the pro minty will be on a blackboard and it needs to be more generic. This is very specific. I just wanted to do my first microcontroller baseboard, and i'm also going to do this on green, because my chili pepper board is still in production and i just wonder whether the fact that it's red is holding up smt assembly.

So i just need to speed things up, so i'm going to do this on green to see if i can get this thing shipped out a bit quicker. So that's the schematic finished essentially i'll. Leave it there today and come back in the next video with the pcb layout. So for the moment, cheerio.