40pin PIC ICSP Demo Board (PCB and Circuit diagram)

[yngndrw]

Hi everyone,

Well I usually work off of a breadboard or stripboard, but recently some of you may have noticed my post about wanting to start with making my own PCBs.

I've been making lots of PCB designs as practice and I thought I'd make this one - It might be useful to some people here.

It's designed for 40pin PICs. It *Should* be compatible with the PIC18F452 (Read on about C7 !!) and it is designed for the almighty PIC18F4550.

It is designed to go between the PIC and your breadboard in order to perform some of the standard tasks. (Reset, ICSP, Power LED, 20MHz Crystal)

C7 is optional for decoupling the 3.3V output on the PIC18F4550, therefore it is NOT needed on the PIC18F452, but it probably wouldn't cause any harm to leave it there.

It's designed with hand-soldering in mind and is able to be produced on a single sided board with only one jumper. (Although it would be a pain to solder the 2x 20pin headers on the solder side) Also note that there are two components which are designed to sit in the gap of the IC holder, underneath the PIC.

I'm also going to design a SMD version.

I know there are probably boards which do these functions already, but this one might do things differently ? It's my little thanks for all the help you guys have given me recently.

Anyway, it's all attached in the Eagle format.

Suggestions, improvements, comments ?

Please note that this has not been tested.

 

[blueroomelectronics]

You'll need a couple of 0.1uf decoupling caps on both VDD & VSS pairs, also since it's a 18F4550 with the VUSB cap adding a USB-B connector might be a good idea IMHO.

 

[yngndrw]

Would just adding a single 0.1uF capacitor next to the 10nF which is under the IC be fine ? Seems as adding two would just make it the same as a 0.2uF capacitor ? In the SMD version I'll make sure the capacitors get placed right next to the pins, one per pair. To be honest, I'm not using any capacitors except a 47uF a bit away from my PIC on the supply rail with no problems, so surly for testing pruoses they don't make much of a difference ? I'll be sure to add any that you suggest anyway - There's plenty of room in the IC socket.

The reasons why I didn't add a USB connector was because of:
1) I intended the circuit to work with more than just the PIC18F4550.
2) I run out of space, the board's height is the max allowed in the lite version of Eagle and the width is just thin enough to only take up one column in a standard breadboard.

However for the SMD version I will add one. I guess it can always be left off if a different PIC is being used.

Thanks for your suggestions.

Edit: I also think that the layout could be used to produce the board with this technique: http://elm-chan.org/docs/wire/wiring_e.html (For people who can't make PCBs)

 

[blueroomelectronics]

The trick with bypass caps is trying to keep the as close as possible to the the ICs power pins. I didn't notice the 10nf under the PIC in your first post. Should do the trick fine. 0.1uf and 0.01uf caps are often similar in size and it's not to hard to pack a pair of them under the PIC.
PS some sockets have a center bar or bars.
**broken link removed**

 

[yngndrw]

Ah okay then. I'll be sure that the SMD version has caps as close as possible while still being solderable.

I designed it when I got a turned pin IC socket. (I normally use the cheap ones for stripboards, but I wanted one for my breadboard) It seems to have a lot of space under it as the turned pins seem to stand it off a little more. Also the center bars should be easy to cut out although I did design it with a socket in my hand so the components under the socket *should* fit nicely in the gaps - Don't hold me to that though.

 

[yngndrw]

New version. I had a go at making the SMD version, but the problem is that there isn't enough space to convert the SMD IC into a DIL pinout. (First pic) There was no space to run any more tracks, nevermind placing components.

Anyhow, V1.1 has lost the capacitor for VUSB. It has however gained an extra set of headers. (Green is my colour for bottom-side silk screen) It's also slightly shorter due to the loss of the capacitor.

The next board that I'll make will sit on top of this and will have the capacitor and socket for the USB. It will also allow RB4 to be used as a VBus sense. Finally it will have another power LED, a 7805 regulator (With power jack) and another reset switch. It might get a power switch too. If I have the space, I'll see about adding a COM port.

C&C ?

 

[justDIY]

make the layout a bit wider, so your ground pour can wrap around the outside of the pins ... then you won't need to rely on that single jumper to connect the two halves of the ground plane together.

 

[yngndrw]

The reason for it being that specific width is so that it can be used on this style of breadboard (Attached pic stolen from Google) without taking up any more columns than required. (The red lines drawn on show where the down-facing pins will go. The up-facing pins are the ones set in slightly.)

Would the only reason to do that be to remove the wire link, or is there some other reason like due to interference ?

Edit: Damn thing won't attach, so here's the link:
**broken link removed**

Basically, it spans a column of 5 holes and the little IC gaps eather side of that column.

 

[blueroomelectronics]

If you're omitting the VUSB and USB stuff why not use a 18F4620, it's a teriffic PIC. You also can omit the crystal.
My Unicorn kit was designed as a general purpose 18F4550 trainer.
**broken link removed**

 

[yngndrw]

Wel the USB stuff was going to be moved onto the next layer. I guess that on a breadboard, height is the one bit of space we oftern overlook.

I'll look into the PIC18F4620, chances are that the board would support it anyway without modification. Maybe the crystal can be on another layer, along with the USB stuff and voltage regulator. It can then be set to the correct pins with jumpers.

The main reasons for me making this are: (I guess I should have specified these earlier)
1) Practice for my PCB making.
2) Something to save me time when using PICs in my breadboard.
3) Hopefully save some space on the breadboard.
4) Was going to be practice for SMD, but as you can see in the picture above, it didn't really work out.
5) Because I lack the money to pay for the shipping of pre-made stuff which mainly seems to be produced in the USA and Canada.
6) Prototyping kits tend to limit your projects to so many of 'X' inputs / outputs. What happens after R&D, when you get onto actually prototyping. Is it not easier to have a board that you can use in a breadboard which does not limit you, but helps you in the required elements. (I.e. ICSP, crystal (On jumpers), USB (On jumpers), +5V regulator (On jumpers))

Actually, other than Dipmicro (Who only seem to stock your Inchworm+ kit) are there any other online retailers for your kits ?

 

[3v0]

I started down the same road but opted to go with a system of interconnected credit card sized boards shamelessly inspired by Nigel's tutorials. Actual size is 2.7 x 1.7 inch (70x44mm)

Ribbon cables (2x5 pin connectors) hook various boards to the processor board. The signal layout is the same as Nigel's with 1=GND and 10=Vcc.

A breakout board connects to the breadboard by converting from 2x5 to the 1x10. It also has LEDs to indicate the state of each line.

So far I have

Two 18 pin PIC processor boards one with 8 pin I2C socket
RS232
IR TX, RX board
600mA HBridge (layed out with parts on order)
2x5 to LCD
​

I plan to add some more powerful processors, RS485, and radio RX TX boards.

The boards all slide into a Radio Shack project box, sort or a mini rackmount. Most of the time they are used without the box.

The one thing that I do not care for is hardwiring the boards to use specific bits. Thinking about using machine turned sockets with jumpers to do the bit assignments.

 

[blueroomelectronics]

Actually, other than Dipmicro (Who only seem to stock your Inchworm+ kit) are there any other online retailers for your kits ?

I'm working on Dontronics as a supplier. I'd love to get a UK distributor.

What programmer do you use?

 

[Nigel Goodwin]

I'm working on Dontronics as a supplier.

You might mention to Don that I'm very pleased with the quality of your boards?, just as I am with Don's - me and Don go back a LONGGGG! way

 

[yngndrw]

3V0: Thanks for the advice, I'll have a think about that route. I guess using wire jumpers is the best way of selecting other than having a matrix of DIP switches. Maybe you could cross the idea of breakout boards and bread boards by having a right angled 1x10 female header on each board and use separate wire links between them ?


blueroomelectronics: I'm using a PicKit2 clone, so it is a great little USB programmer but has no real ICD capabilities. I bought it before I found this site and to be honest if I'd have found this site before I found the PicKit2, I'd have contacted you about getting an Inchworm+ and Unicorn set shipped over here based on the amount of good reviews about your products on here ...

For distributing, have you looked into direct sales ? I.e. Having an E-Commerce setup and shipping them from your own home ?


I think I'll keep this design project on hold while I think a bit more about what 3V0 uses .. Nigel's tutorials are extremely good and he obviously made those boards for a reason.


Nigel: How about a few of the tutorials done in MC's C18 ? Would be interesting to see how others find solutions and methods of programming PICs in C.

 

[Nigel Goodwin]

Nigel: How about a few of the tutorials done in MC's C18 ? Would be interesting to see how others find solutions and methods of programming PICs in C.

I've never used C, and never liked C - but really the 18F chips require it, as even many of the application notes are written using C. So I may get round to it one day!

 

[blueroomelectronics]

I've never used C, and never liked C - but really the 18F chips require it, as even many of the application notes are written using C. So I may get round to it one day!

Ditto, me too. Microchips TCP/IP stack is all C and if you want to play with the ENC28J60 well kind of tough with no C knowledge. I can program in ASM, BASIC & PASCAL but never learned C.

I find I "think" along the lines of the assembly language.

PS the PICKit2 should have debug support for some PICs.

 

[yngndrw]

Yay I can reply now.

Ahh, I guess I was lucky (Or unlucky ) in that I already knew C from x86 programming before I started with PICs. It sure does make things easier, but you can sometimes get carried away and forget that you're only running the code on a little tiny PIC as opposed to a dual core PC.
I found the support list for debugging with the PICKit2 so small that it wasn't worth it, I'll have another look though.