Suggestions for building a PIC dev. board?

[chopnhack]

It is not that difficult to solder a 44-pin TQFP. I have done several of them. It actually takes less time than soldering a 40 pin DIP because you just drag the solder across all of the pins then wick off the excess. You should try it. Get a breakout board of Ebay, look at some YouTube videos and you should be all set.

Then, once you design the board, you can get 10 from China really cheap, and just make up a new board for each project.

Bob

Agreed, I just had some beginners luck on a project that had a 8 pin soic that I drag soldered and it was a breeze - I think the trick is to solder underneath a layer of flux gel. My point was that with a dev. board, you should be able to easily insert and remove the chip to go from tinkering on the board for proof of concept to then install it in the project board. How would you be able to reuse your 44 pin pic? I would think it would be a bear to remove that one from the breakout board.

 

[KrisBlueNZ]

My initial thoughts were to use a 40 pin zif with female header strips on either side of the zif socket.

I agree with the female socket strips along both sides, but I'm not sure about using a 40-pin ZIF socket - you're not likely to be removing and refitting devices much (since you'll have an ICP connector on the board), and machine screw sockets like on the Gooligum board would be cheaper, and you should be able to squeeze some 0.3" span sockets inside the 0.6" 40-pin ones. Of course, you can make the decision between machine screw sockets and a single ZIF socket at the time when you assign the board to a project.

Also, I agree with Bob that you're not likely to need to remove the PIC once you've allocated the board to a project, and the PCB itself will be cheap. But that's not the full story because of the cost of the optional circuitry - for example, H-bridge ICs aren't cheap and you might not want to install them on every board you get, and it's not ideal to be installing them after the PIC has been fitted. But once you have an idea for a project to allocate a blank board for, you could install the required support components, then install an SMT PIC device, and commit the board to that project, so effectively, Bob is right, I think.

Like I said initially, I don't know what I don't know! I would think a few 7 segment LED's, perhaps a LCD, some simple LED's as indicators, a speaker..

Yes, something like that. Download the data sheets for a variety of PICs and use them to determine the common pin allocations - for example, a lot of them have VDD and VSS on the northernmost pins - and to see what peripherals they have and how they can be routed to pins. Create a document - perhaps on Google Docs - listing the devices, their peripherals and their pin allocations. Then add support circuitry on the board.

I suggest adding support for a 32 kHz watch crystal for timekeeping, possibly along with a battery backup circuit; some motor driving circuitry (with a separate supply rail) - three or four single-ended drivers for stepper motors, and two or three H-bridges for brushed DC motors or stepper motors, and other circuitry to support the PIC peripherals that interest you.

The Gooligum board is probably a good source of information again. It looks like it uses 0.1" pin headers and jumper shunts to connect PIC pins to external circuitry.

 

[chopnhack]

I agree with the female socket strips along both sides, but I'm not sure about using a 40-pin ZIF socket - you're not likely to be removing and refitting devices much (since you'll have an ICP connector on the board), and machine screw sockets like on the Gooligum board would be cheaper, and you should be able to squeeze some 0.3" span sockets inside the 0.6" 40-pin ones. Of course, you can make the decision between machine screw sockets and a single ZIF socket at the time when you assign the board to a project.

Also, I agree with Bob that you're not likely to need to remove the PIC once you've allocated the board to a project, and the PCB itself will be cheap. But that's not the full story because of the cost of the optional circuitry - for example, H-bridge ICs aren't cheap and you might not want to install them on every board you get, and it's not ideal to be installing them after the PIC has been fitted. But once you have an idea for a project to allocate a blank board for, you could install the required support components, then install an SMT PIC device, and commit the board to that project, so effectively, Bob is right, I think.

Yes, something like that. Download the data sheets for a variety of PICs and use them to determine the common pin allocations - for example, a lot of them have VDD and VSS on the northernmost pins - and to see what peripherals they have and how they can be routed to pins. Create a document - perhaps on Google Docs - listing the devices, their peripherals and their pin allocations. Then add support circuitry on the board.

I suggest adding support for a 32 kHz watch crystal for timekeeping, possibly along with a battery backup circuit; some motor driving circuitry (with a separate supply rail) - three or four single-ended drivers for stepper motors, and two or three H-bridges for brushed DC motors or stepper motors, and other circuitry to support the PIC peripherals that interest you.

The Gooligum board is probably a good source of information again. It looks like it uses 0.1" pin headers and jumper shunts to connect PIC pins to external circuitry.

I had the zif on hand so I figured on using it for something. It must be my misunderstanding then, I thought the purpose of a dev.board was for learning and testing out how chips work, without the chip becoming a permanent addition to the board. That is what I thought also when I saw the Gooligum board used a dip for inserting chips.

If I understand what you are saying, Kris - it sounds more like the MicroE's click boards approach to their EasyPic product? With one PIC permanently mounted that serves as the brains and then additional plug in modules, some with pic's as well.

 

[KrisBlueNZ]

Well, it depends what you want. You can have one board with all the peripherals on it, like the Gooligum board, and just use it for prototyping and do a completely new layout for each project, but if you only want one or two boards for a particular application, it's more economical to design a generic board, get a batch made, and just populate the bits you need for each project.

The Click boards are a bit different. I'm not suggesting multiple boards at all - just a single layout that you populate differently for each project according to its requirements.

 

[BobK]

Yes, that is what I was getting at.

Bob

 

[chopnhack]

but if you only want one or two boards for a particular application, it's more economical to design a generic board, get a batch made, and just populate the bits you need for each project.

As for a generic board, what would you include on that kind of board? Power supply in, pic, associated passives, icsp, some type of pin out header...? What else for a generic board?

 

[KrisBlueNZ]

Yes, exactly. All of that, and perhaps some flexibility for powering options - 5V and 3.3V regulators, and jumpers between them and VDD, and VDD brought out to the power connector too, so it can be powered directly from an external supply.

I suggested some types of support circuitry in post #22. I suggest you choose a selection of devices to support, look at the peripherals they have, try to imagine how you might want to use those peripherals, and think about what support components would be needed.

Download a lot of application notes from Microchip to suggest things they can be used for; these will include circuitry and component suggestions to support the relevant peripherals.

I would use a table to keep track of peripherals and work out how pins from different PIC positions should be commoned together, or have separate jumpers for each PIC position. And of course all I/O points should be available on socket strips.

The peripherals may need special support circuitry, but there's also a need for general purpose I/O such as open collector or open drain outputs, and inputs from contacts (pullup resistor to VDD, then series resistor to the I/O point).

Microchip application notes would be the best starting point to get ideas for what the PIC can be used for, and what external circuitry would be useful.

 

[mikejp56]

Hi chopnhack,
Nice name for an electronics guy! Anyway, if you are still interested in building your own development board, perhaps I can help you out. Last winter I wanted to get into PICs and did the legwork and homework and built my own development board. It has the following:
8 LEDs
4 tactile pushbuttons
Serial EEPROM
16x2 parallel LCD
DS18B20 temperature sensor
DHT22 temperature and humidity sensor
piezo buzzer
pot adjustable 0-5V
integrated USB programmer
40 pin ZIF socket
8,14,18, and 28 pin sockets on a 40 pin adapter board
external crystal socket

I did extensive research on this board , and I am quite happy with the way it turned out. It is built on a 6"x6" vectorboard and hand soldered. Single inline headers are used to connect to all of the peripherals, and wire jumpers with pins are used to make the connections.
If you are interested I can post the schematic, BOM, and a photo of how it looks.
Regards,
mikejp56

 

[chopnhack]

Nice name for an electronics guy!

Hi Mike, LOL yes, thanks - it comes from my woodworking background, but it applies here too, well at least the hack bit! Ha

Welcome to EP!!

I did extensive research on this board , and I am quite happy with the way it turned out

I can imagine, you did quite well to integrate multiple chip sizes, well done!

If you are interested I can post the schematic, BOM, and a photo of how it looks.

Absolutely, I would love to see what you came up with! I ended up building a dev. board specific to one chip - the 12F675 that I was working on for another project.

Thanks for stopping by, how did you come across this old thread?

cheers

 

[mikejp56]

Hi chopnhack,
Just browsing the forums. The experimenter board has USB PIC Prog incorporated into it for the programming of PICS. A better schematic and all the files needed can be found at USBPICPROG.ORG.
Good luck!
Regards,
mikejp56

 

[chopnhack]

Hi chopnhack,
Just browsing the forums. The experimenter board has USB PIC Prog incorporated into it for the programming of PICS. A better schematic and all the files needed can be found at USBPICPROG.ORG.
Good luck!
Regards,
mikejp56

Your schematic looks great, I like the use of buses to keep the layout clutter free. Is this board built around the 16f887 or are you able to swap in other pin compatible pic's. My initial thought was to produce a board that could accommodate as many pic chips as possible - obviously changes between families would necessitate a new board (i.e. pic32's)
Any pictures?