**FINished layout at end of this thread. (Page 2)
Paul
**
To all who love GCBasic but hate birds nest wiring:
I am about to layout a general purpose board using 18F26K20. (Other pics will probably be compatible)..
Any suggestions on making this board versatile for projects would be helpful.
.
Currently the board layout will have a 7805 regulator, two power FETS with Drains brought out to block terminals, power and ground brought out to screw block terminals, all IO pins brought out to pin header on edge of board. Of couse you can use any componets you require, not just the ones in the layout or schematic.
Lots of decoupling caps and a ground plane.
Two LEDs with resistors to two ports, 1 pot connected to one A/D port, position for resonator or xtal.
These peripherals can be left off if desired and use the pin header.
When I order these boards I get 3 for $41 (or 3 for $61 with silk screen and solder mask).
I try to keep the layout area within the dotted lines and place two identical layouts, thus getting 6 boards for $40.
I will gladly give the layouts to anybody who wants them (and schematic). These board are done with ExpressPCB, so the files will be in that format.
See the PCB below, keep in mind all the components are currently just thrown on the board for area check, they will be moved around as I apply the traces (two sided, plated thru holes).
.
If any interrest, it will be a couple of weeks befor layout is complete.
See the attached board info.
.
I'll post a schematic Monday to give you an idea of the options.
**PLEASE SEE LAST POST FOR FINAL
**
Last edit: Paul Haug 2017-05-13
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I like 28pin dil pics so I knock out these. Tried printing a b/w pcb image onto paper with a laser printer and ironing it onto copper clad board for a few mins then etching?
I suggest you have your 5V regulator supply a 3V3 regulator too.
That way you have both supplies available.
Many new devices that you may wish to use or interface to are 3V3 only these days.
I would also suggest that you have two more LED’s so you have 4 one one port for counting etc.
Also include a reset button, connected to the Mclr Pin - It is almost indispensable when prototyping or experimenting. On many devices a config setting can be used to turn the Mclr pin into an input, so a single button can be dual purpose here.
Finally, provide jumper links on your oscillator inputs so that the internal oscillator can be used in place of the crystal and optionally free up those two pins.
Cheers
Chris
Last edit: Chris Roper 2017-04-23
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Chris,
Here are my replies to your suggestionsin same order, good ones.
1> You can repace the 5V regulator with a 3.3 V regulator.
2> I will add two more LED as suggested.
3> I will add a push button to the MCLR
4> All pins 1 thru 24 are available on the 24 oin header, so those pins are available
if the resonator/xtal is not installed.
Thanks for the suggestions, keep em coming.
I am building this not as a prototyping board
but as a base to connect to a prtotying board or system.
Also the 20 pin header will be able to plug in directly to prtotyping board if you mount the header on the bottom of the pc board.
.
Of course the acual layout is free (when it's done)
Last edit: Paul Haug 2017-04-28
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It still think you should have both 5V and 3V3 available at the same time, not one or the other.
All the modern boards do that now and it is often useful.
A simple jumper will allow you to switch the default supply to the PIC yet have both available on the expansion header.
Remember many PIC’s come in two flavors, the PIC16Fxxxx and the PIC16(L)Fxxxx, the latter being identical but low voltage and power. You may develop with the 16F device at 5V then decide to switch to the 16LF device at 3V3 to make a battery operated version. The same code and hardware would then work for both cases.
Your resistor values would remain the same, an LED with a 1K current limit on 3V3 is still bright enough for all but reading by.
Cheers
Chris
Last edit: Chris Roper 2017-04-23
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Currently the board layout will have a 7805 regulator, two power FETS with Drains brought out to block terminals, power and ground brought out to screw block terminals, all IO pins brought out to pin header on edge of board. Of couse you can use any componets you require, not just the ones in the layout or schematic.
If you would like to refer to this comment somewhere else in this project, copy and paste the following link:
Remember many PIC’s come in two flavors, the PIC16Fxxxx and the PIC16(L)Fxxxx, the latter being identical but low voltage and power. You may develop with the 16F device at 5V then decide to switch to the 16LF device at 3V3 to make a battery operated version. The same code and hardware would then work for both cases
Yes, that is a good reason, I will do that. Thanks.
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A 3.3V Regulator or at least pads for one a must for me. Many peripheral devices such as RF modules and others require 3.3V.
The Microchip Curiosity Low Pin Count Board is a pretty good example of a decent and inexpensive Dev Board. Can be Powered by USB or externally if you add the optional 5.0V regulator. Has an Onboard Pickit 3 (PKOB) and also supports an external Pickit3 if you wish.
I have added a 3.3 and 5 volt reg TO222 (or any oin compatable), so my question now, should the pickit3 pin 2 go to the selectable voltage, or does it have to 5 V only.
Last edit: Paul Haug 2017-04-23
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The PICKit3 will sense the power supplied to the PIC Socket and set its internal levels appropriately, so just connect the Vdd and Vss from the ICSP header directly to the socket, no need to worry about the actual voltage selected by the onboard power.
If you would like to refer to this comment somewhere else in this project, copy and paste the following link:
I use a low dropout regulator because the boards end up in robots that use 2x 3.6v lipos. The reg at low current regulates to 5.8V. Level shifters would be useful and depending,maybe pins outs for servos and i2c. maybe serial pinsout. Some easy way to pull lines up or down. A zif socket for all devices could be implemented. Your project though. Afterthoughts when you've made a pcb are fun.
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Here is the layout so far.
I will try to incorperate an 8 led lightbar, for ctr display or other..
Still in flux so a lot of hookup is not in place, as a lot of componets
.
Last edit: Paul Haug 2017-04-23
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For 28 pin have you considered the CHIPINO?
I designed it many years ago so I could use Arduino shields with PIC.
Its designed to accept a PICkit programmer and has both 5v and 3v regulator.
Design is open source non-commercial and in ExpressPCB format.
See more at chipino.com
Also available at howtronics.com (the only approved reseller).
If you would like to refer to this comment somewhere else in this project, copy and paste the following link:
Thanks Chiuck. Yes I did consider other exsisting boards, but I decided to do my own for a fit into a couple of exsisting projects, thus the 2 channel A/D inputs with RC filtering, and the two FET power drivers. Then I decided to make it as usefull as posible for other projects and other users.
Attached below is the preliminary schematic incorporating other suggestions.
I will probably add Brd Bd thru hole pads to any area left over for custom ckts, it won't be much.
Hmm.. I think the uno is..well numero uno for best product for price re dev board but a pic version,28 pin 16f876 is pinny like 18f25k22 a bit,well a lot and I use both so a uno sized board thingy would be nice. Please make one for me :) no more vero.
OK Stan, you convienced me. I will continue the layout for the 28 pin 18F25K22 since I have these o hand.
Paul should clean up your wiring a lot.
When I finish and get some board I will send you one.
Last edit: Paul Haug 2017-04-24
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Nice one Paul but that's ok.Nothing I make ends up in a box.PCB's are a bit permanent but an arduino sized board with lots of in out pins and power pins would be nice. The simple boards I knock out cost £1 ,reg,socket,pin strip,caps,vero and take 10 minutes to build. I don't get capacitance problems with parallel tracks. PCBs can have large planes.
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Well, it is comeing close. I decided to ad vector board layout to the right side to make it more useful.
The right side is not complete, so any suggestions would be appreciated.
I can still cut it along the dotted lines to make the right side small enough for my project.
Note that the header pins 1 thru 28 are directly connected to the corresponding 28 PIC pins
;
Last edit: Paul Haug 2017-04-28
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**FINished layout at end of this thread. (Page 2)
Paul
**
To all who love GCBasic but hate birds nest wiring:
I am about to layout a general purpose board using 18F26K20. (Other pics will probably be compatible)..
Any suggestions on making this board versatile for projects would be helpful.
.
Currently the board layout will have a 7805 regulator, two power FETS with Drains brought out to block terminals, power and ground brought out to screw block terminals, all IO pins brought out to pin header on edge of board. Of couse you can use any componets you require, not just the ones in the layout or schematic.
Lots of decoupling caps and a ground plane.
Two LEDs with resistors to two ports, 1 pot connected to one A/D port, position for resonator or xtal.
These peripherals can be left off if desired and use the pin header.
When I order these boards I get 3 for $41 (or 3 for $61 with silk screen and solder mask).
I try to keep the layout area within the dotted lines and place two identical layouts, thus getting 6 boards for $40.
I will gladly give the layouts to anybody who wants them (and schematic). These board are done with ExpressPCB, so the files will be in that format.
See the PCB below, keep in mind all the components are currently just thrown on the board for area check, they will be moved around as I apply the traces (two sided, plated thru holes).
.
If any interrest, it will be a couple of weeks befor layout is complete.
See the attached board info.
.
I'll post a schematic Monday to give you an idea of the options.
**PLEASE SEE LAST POST FOR FINAL
**
Last edit: Paul Haug 2017-05-13
I like 28pin dil pics so I knock out these. Tried printing a b/w pcb image onto paper with a laser printer and ironing it onto copper clad board for a few mins then etching?
Here is the preliminary schematic and begining board layout.
NOTE: Board layout does not match schematic at this time....
Last edit: Paul Haug 2017-04-23
Stan,
I revised the layout for 28 pin devices.
Last edit: Paul Haug 2017-04-28
I suggest you have your 5V regulator supply a 3V3 regulator too.
That way you have both supplies available.
Many new devices that you may wish to use or interface to are 3V3 only these days.
I would also suggest that you have two more LED’s so you have 4 one one port for counting etc.
Also include a reset button, connected to the Mclr Pin - It is almost indispensable when prototyping or experimenting. On many devices a config setting can be used to turn the Mclr pin into an input, so a single button can be dual purpose here.
Finally, provide jumper links on your oscillator inputs so that the internal oscillator can be used in place of the crystal and optionally free up those two pins.
Cheers
Chris
Last edit: Chris Roper 2017-04-23
You may find the examples and the Schematic Drawings in the Document usefull as a guide and Ideas for a minimal 20 PIN board:
http://ww1.microchip.com/downloads/en/DeviceDoc/Low%20Pin%20Count%20User%20Guide%2051556a.pdf
and here is the equivelent for a 28 Pin demo board:
http://ww1.microchip.com/downloads/en/DeviceDoc/41301A.pdf
Have fun, I have built several boards but the two included here are my base line referance.
Cheers
Chris
Chris,
Here are my replies to your suggestionsin same order, good ones.
1> You can repace the 5V regulator with a 3.3 V regulator.
2> I will add two more LED as suggested.
3> I will add a push button to the MCLR
4> All pins 1 thru 24 are available on the 24 oin header, so those pins are available
if the resonator/xtal is not installed.
Thanks for the suggestions, keep em coming.
I am building this not as a prototyping board
but as a base to connect to a prtotying board or system.
Also the 20 pin header will be able to plug in directly to prtotyping board if you mount the header on the bottom of the pc board.
.
Of course the acual layout is free (when it's done)
Last edit: Paul Haug 2017-04-28
It still think you should have both 5V and 3V3 available at the same time, not one or the other.
All the modern boards do that now and it is often useful.
A simple jumper will allow you to switch the default supply to the PIC yet have both available on the expansion header.
Remember many PIC’s come in two flavors, the PIC16Fxxxx and the PIC16(L)Fxxxx, the latter being identical but low voltage and power. You may develop with the 16F device at 5V then decide to switch to the 16LF device at 3V3 to make a battery operated version. The same code and hardware would then work for both cases.
Your resistor values would remain the same, an LED with a 1K current limit on 3V3 is still bright enough for all but reading by.
Cheers
Chris
Last edit: Chris Roper 2017-04-23
Currently the board layout will have a 7805 regulator, two power FETS with Drains brought out to block terminals, power and ground brought out to screw block terminals, all IO pins brought out to pin header on edge of board. Of couse you can use any componets you require, not just the ones in the layout or schematic.
Yes, that is a good reason, I will do that. Thanks.
A 3.3V Regulator or at least pads for one a must for me. Many peripheral devices such as RF modules and others require 3.3V.
The Microchip Curiosity Low Pin Count Board is a pretty good example of a decent and inexpensive Dev Board. Can be Powered by USB or externally if you add the optional 5.0V regulator. Has an Onboard Pickit 3 (PKOB) and also supports an external Pickit3 if you wish.
I took one of the LPC Curiousity boards and mouted it to 1/2 of a Large 1660 Pin Breadboard
Did the same with the Curiousity HPC but had to hack that one to provide exterrnal power as it does not have the external power option.
It's not unusual for me to have 2 or 3 PICs ( with Bootloaders) on the Breadboard and 1 on the LPC board at the same time.
Last edit: William Roth 2017-04-23
I have added a 3.3 and 5 volt reg TO222 (or any oin compatable), so my question now, should the pickit3 pin 2 go to the selectable voltage, or does it have to 5 V only.
Last edit: Paul Haug 2017-04-23
The PICKit3 will sense the power supplied to the PIC Socket and set its internal levels appropriately, so just connect the Vdd and Vss from the ICSP header directly to the socket, no need to worry about the actual voltage selected by the onboard power.
I use a low dropout regulator because the boards end up in robots that use 2x 3.6v lipos. The reg at low current regulates to 5.8V. Level shifters would be useful and depending,maybe pins outs for servos and i2c. maybe serial pinsout. Some easy way to pull lines up or down. A zif socket for all devices could be implemented. Your project though. Afterthoughts when you've made a pcb are fun.
This is just a cd4050 level shifter...bit messy,true.
Here is the layout so far.
I will try to incorperate an 8 led lightbar, for ctr display or other..
Still in flux so a lot of hookup is not in place, as a lot of componets
.
Last edit: Paul Haug 2017-04-23
For 28 pin have you considered the CHIPINO?
I designed it many years ago so I could use Arduino shields with PIC.
Its designed to accept a PICkit programmer and has both 5v and 3v regulator.
Design is open source non-commercial and in ExpressPCB format.
See more at chipino.com
Also available at howtronics.com (the only approved reseller).
Thanks Chiuck. Yes I did consider other exsisting boards, but I decided to do my own for a fit into a couple of exsisting projects, thus the 2 channel A/D inputs with RC filtering, and the two FET power drivers. Then I decided to make it as usefull as posible for other projects and other users.
Attached below is the preliminary schematic incorporating other suggestions.
I will probably add Brd Bd thru hole pads to any area left over for custom ckts, it won't be much.
Last edit: Paul Haug 2017-04-24
Makes sense. Plus its fun to design your own.
Hmm.. I think the uno is..well numero uno for best product for price re dev board but a pic version,28 pin 16f876 is pinny like 18f25k22 a bit,well a lot and I use both so a uno sized board thingy would be nice. Please make one for me :) no more vero.
OK Stan, you convienced me. I will continue the layout for the 28 pin 18F25K22 since I have these o hand.
Paul should clean up your wiring a lot.
When I finish and get some board I will send you one.
Last edit: Paul Haug 2017-04-24
Nice one Paul but that's ok.Nothing I make ends up in a box.PCB's are a bit permanent but an arduino sized board with lots of in out pins and power pins would be nice. The simple boards I knock out cost £1 ,reg,socket,pin strip,caps,vero and take 10 minutes to build. I don't get capacitance problems with parallel tracks. PCBs can have large planes.
Not many traces yet, but I think the general componet layout is down...
Last edit: Paul Haug 2017-04-25
Well, it is comeing close. I decided to ad vector board layout to the right side to make it more useful.
The right side is not complete, so any suggestions would be appreciated.
I can still cut it along the dotted lines to make the right side small enough for my project.
Note that the header pins 1 thru 28 are directly connected to the corresponding 28 PIC pins
;
Last edit: Paul Haug 2017-04-28
The layout does not preclude up to 40 pin skinnydip if you ignor the silk screen layer, or any combo of dips.
.
EDIT: Final layout shown nex page
.
Last edit: Paul Haug 2017-05-03