Free PCB to the most helpful two replies (PIC Tutor)

I'm going to build one of three PIC based microcontroller projects for sale to students and hobbiests etc.

They may all eventually get built but I can't figure out which to build first and did I miss something vital.

So the two best replies (as chosen by myself and I will include the reason) will get a PCB of the winning project free.

All designs are meant to work with and compliment the Inchworm ICD2. Also the approximate retail prices in CDn dollars.

The first design Firefly $25 - $39 is a combination of PIC ZIF programming socket and 16F88 Tutor. Can be built as just a trainer, ZIF or both. Although the Firefly seems simple you really can program and learn almost all the features of 16F88 and there are many, almost everything a 16F877 has with fewer pins, way to use SSP (I2C slave / SPI) though.

• 40 pin ZIF socket for 16F & 18F series 8/14/18/28/40pin PICs
• 16F88 can be programmed independantly of the ZIF
• IR (New not yet in schematic, can be switched RB0)
• 3 BiColor Red / Green LED muxed
• 3 Pushbuttons
• RS232 in hardware half duplex inverters
• POT
• 2.5V approx vref (may include a TL431 option)
• Connectors: User (iButton, etc), Servo / Buzzer etc.

The second design Dragonfly $69 is a 16F877A designer / prototyping board.

• 16F877A @ 4MHz (suggestions?)
• 16x2 LCD with backlight
• 4x4 switch array
• RS485 with simple RS232 mode (jumper selectable)
• 350 slot solderless breadboard
• IR, POT, Pushbutton
• Connectors for: iButton, I2C, ICD2, 2 x Servo/CCP
• 20pin expansion (for possible SPI UART or Ethernet, etc)

The third design Gryphyn $19-$29 (currently incomplete details will be on my update site as they become available) is a small PCB that can be built on one of three ways. Will use a 16F87 or 16F873A depending on feedback, the larger PIC will allow for a 4x4 keypad in all modes. Usually there's a spare I/O or two in any configuration (ie: iButton)

1. I2C (hardware) or serial (software) to 16x2 LCD including backlight
2. I2C or serial to 4 Digit 7 segment display
3. I2C or serial to 4 Relays and 4 Switch inputs

See this page on my site for schematics (click to enlarge...)

**broken link removed**

https://www.mikroe.com/en/tools/easypic4/

1. 36 diodes for displaying states of all pins on the microcontroller at the same time.

2. Crystal can be removed and replaced by another one.

3. 2 potentiometers for testing multiple AD conversion and comparators.

4. Pull up or Pull down port defining.

The firefly would be a nice intro board. Learning the switches, lighting the LED, and can talk to a PC via RS232. IR as well, play with your TV remote.. It is a nice starter board.

The Dragonfly though, that would be more hobbiest to me, with proto type area. And LCD is nice, but unless they are using a high level language, would be for a more advanced student I would think..

I think both would be popular though.

are you comparing the Dragonfly to the easypic 3?
I've never used an easypic3 and it looks like a neat board.
Its hard to compare but here goes
Dragonfly
Mplab using debug built into 16f877a
4"x6" fits hammond sloped case
Solderless breadboard is more flexible than any prebuilt.
Rs485 standard
Ir standard
4x4 + 1 keypad
Its about half the price of the easypic3, (not including the inchworm) on the cheap I could preinstall a bootloader but the point is programming without an ice or debugger is much harder than with one. You can build it yourself, some sense of satifaction in that.

Easypic3
Lots of buttons, jumpers, sockets, leds, lcds, 7 segment displays, usb programmer.
Debug appears to be done with a simulator.
Size? Looks about 8x10
Graphic lcd option. Expandable (did I mention lots of jumpers)

Lastly if you're comparing to firefly.
$20us vs $120us and the firefly can probably teach you enough that you would be ready to build your own devices. Afterall a inchworm + firefly with zif + PICBASIC Pro and you can beat a BASIC Stamp and or PICAXE in speed, program size and price (price per PIC) and there's a great free c compiler that supports mplab (mplab is the one to learn) cc5x

Imho

The second pot seems to be popular.
I was thinking of putting a jumper on ir & rb0 on the dragonfly.

As for 32leds it takes money & pcb space. The debugger is a much more elegant way of viewing your I/O port status than leds.

The crystal I could socket or jumper, some people like to blink leds with 20mhz clocks...

I'm tending towards the firefly, its smaller, eaiser to design, fits a students & hobbiest budget. And I can write a book about it.

All this started because I wanted to build a thermostat with an rs485 port (cricket)

I am not comparing...
U can pick up some things from that borad,
as i like 36 diodes for displaying states of all pins on the microcontroller at the same time.

The Firefly would be the more attractive option to me. The main addition I would suggest would be to add a solderless breadboard, if it doesn't alread have one. I agree completely with your choice of a bigger ZIF than needed for the F88. Hopefully, the pins from the other end will be brought out, so the user can use the same setup and breadboard for smaller chips, such as the 12F series. As a hobbyist interested in specific, non-commercial projects, I have had no need for the bigger, high-pin count chips. I like the idea of small, dedicated chips. Also, as a newbie to PICs, my designs still incorporate some analog and mixed signal devices, thus the need for a breadboard. The switches, LEDs, and particularly the textbook would be invaluable. May I suggest you stress Assembly rather than Basic.

I suspect your other devices would tend to appeal more to the other end of the market. So, the real question to me would be which end of the market you want to address, not which concept is more useful. Good luck. John

On the Firefly, ff the breadboard were added, 4x4 switches and a couple 7-segment displays. That would cover an entry level person and the more advance. Maybe raise the price a little.

mramos1 said:

On the Firefly, ff the breadboard were added, 4x4 switches and a couple 7-segment displays. That would cover an entry level person and the more advance. Maybe raise the price a little.

Click to expand...

Exactly, and at $30 plus or minus, it would be a bargain. In fact, I was just about to draw and etch the board for a simplier version myself. I am tired of my current Rube Goldberg set-up. It would not have to come assembled or even with parts for that matter. John

A solderless breadboard with the firefly would simply sit beside it. The zif sockets barely has any free pins. I thought about a resonator when a 16f873a was installed, still not much i/o because of the programming and power wires.

In a kit is good (lower cost). If they are ordering that item, they should be able to assemble it. And the pride in saying they built it.

No parts would work for the more advanced (or the ones that know how to get samples from Microchip or have a good local source for parts). But true, a bare board for the more advanced. I was short 2 parts when I built my Inchworm ICD2 using parts I had at home.

And a nice assembly .pdf and a tutorial (I know where you can hi-jack one; sorry Nigel, just kidding)

William At MyBlueRoom said:

A solderless breadboard with the firefly would simply sit beside it. The zif sockets barely has any free pins.

Click to expand...

Hi Bill,

I use a 28-pin ZIF (plenty of room for an 18-pin F88) and breadboard. The ZIF takes up so much space that sometimes I have to link two breadboards together. That's what I would like to avoid. Your Firefly solution sounds much better, with built-in switches, etc., but running lines between boards would not be ideal. Could the Firefly board be made with keyed "clips" so it could be attached to a breadboard similar to the way some breadboards snap together? John

Instead of just a 4Mhz crystal on the Dragonfy board, you could have a look at using a programable oscillator such as an "exo-3c".
This is an 8 pin chip and comes in various frequencies. eg. A 16Mhz type can be easily patched with 3 pins to give 16Mhz plus a 8, 4,2,or 1Mhz etc output.
See data sheet at https://www.electro-tech-online.com/custompdfs/2006/10/exo3c.pdf

On the firefly. Maybe include the breadboard and a connector (on the firefly like the ICD2 programming cable) that can be plugged into the breadboard and jumpered on the breadboard where they like?

I thought that I saw an answer to this in another thread, but I cannot find it at this time.

What was the reasoning behind including the 12F5xx emulator on the Firefly?

For something that will potentially be marketed to beginners/students/hobbyists, this "feature" seems to be quite out of place.

I really like the idea of the Firefly being a tutor/programming platform when paired with your Inchworm ICD2. The cost and size will be a definite plus.

Perhaps a socketed crystal or multiple crystals with a jumper (or dip switch) to select? Maybe another pot and a couple of 7-segment displays to round everything out?

TekNoir said:

What was the reasoning behind including the 12F5xx emulator on the Firefly?

For something that will potentially be marketed to beginners/students/hobbyists, this "feature" seems to be quite out of place.

I really like the idea of the Firefly being a tutor/programming platform when paired with your Inchworm ICD2. The cost and size will be a definite plus.

Click to expand...

The 12Fxxx bit was added as seen in this web page, you could do much the same thing by putting a 16F87 in the socket and access B0-B5. The added cost is simply a 10/8 IDC pin connector.

**broken link removed**

I find a single 7 segment display of questionable value, don't get me wrong I love LED displays but it's only when you get into muxing them (like charlieplexing) before they become interesting...

The I/O pins were carefully chosen for IMO the best way of using them in such a simple circuit. B0/INT is special for generating edge driven irqs (handy for the jumper selectable IR in the newest schematic). The PWM output or CCP input was given an external use such as a servo, piezo or even an LED. RA2 has a D/A that can be rerouted to vref or a comparator input. Also can be reassigned as power or gnd for a DS18S20 temperature sensor.
RA4 being open collector is almost ideal for iButton & 1wire stuff, and it too is another A/D port. You could hook all sorts of stuff upto the USER port, POTs, Caps, LDRs...
The 10K pot on RA1 is the other half of the comparator that the CVREF controls (your 16 step digital D/A inside the 16F88 or virtual pot#2)
RB0,1,4 have software pullups for the switches, RB4 has IRQ on change to play with. RA0,6,7 you get to play with Red/Green LEDs on a mux similar to charlieplexing. Your software will get busy playing in this mode, good way to learn about timer irqs. The serial port cheap as it is will function in half duplex mode and you can even experiment with bootloaders or hook up a serial LCD display or save your money and just use hyperterminal or something better (tera term comes to mind)
No crystal needed for the 16F88 (it's got an eight speed osc, from 31khz to 8mhz @ 1%)

The ZIF side (40 pin wide ZIF sockets aren't cheap $12CDn) is for those of us who got used to the old style but still popular way of programming.

An osc across pins 9 & 10 of the ZIF would allow you to get the debug mode fired up when a 16F876A was installed but the only I/O pins you'd have access to would be A0 thru A5, RB0 thru RB5, RC2 & RC4. I could put a header out to these pins space permitting you would have to be wary of using the "in use" pins as outputs as you could damage the chip. Same goes for the 12Fxxx simulator too.

Keep in mind those "features" if not installed would add no cost to the board. The're just holes and traces, and even installed just connectors. The connectors would be IDC and work similar to the Tech-Tools IDE (I used to use before I built the inchworm...)
**broken link removed**
On a sidenote I picked up the book "123 PIC Microcontroller Experiments for the Evil Genius" by Myke Predko. This book got mixed reviews on Amazon but Myke is a local and I liked his other books. He uses the PICKIT1 (he solders a ZIF socket to it) plus a handful of circuits. Most of his projects use the 16F684 (I prefer the 16F88 because of the debug mode) and a few of his projects are beyond the scope of the single pushbutton & pot on the PICKIT1 so there are a few schematics you'll need a solderless breadboard for. One I liked was a way to check the accuracy of different PICs by hooking a pair of PICs together with an LED. The Firefly could do this as you can program/run the ZIF PIC (bottom) or the 16F88 (on top) independantly. Of course you can simply jumper a pin from the 12Fxxx socket to one of the USER I/O pins on the 16F88 (you'd need a pair of 16F88 for that)

jpanhalt said:

Hi Bill,

I use a 28-pin ZIF (plenty of room for an 18-pin F88) and breadboard. The ZIF takes up so much space that sometimes I have to link two breadboards together. That's what I would like to avoid. Your Firefly solution sounds much better, with built-in switches, etc., but running lines between boards would not be ideal. Could the Firefly board be made with keyed "clips" so it could be attached to a breadboard similar to the way some breadboards snap together? John

Click to expand...

One half more or less will contain a wide slot 40pin ZIF with the power LED located just above pin #11 (helps spot pin1 on the smaller PICs) The lower half will contain the 16F88 section. It'll be exactly the same size as the inchworm so it will fit a Hammond 1591B case 4.4" x 2.4". The case is optional but will protect the bottom of the PCB and keep from scratching your desk.

Sidenote: a really keen look might be use standoffs and mount the Firefly above the Inchworm. Snazzy in a geeky sort of way.

It looks like I'll sell the Firefly as a bare board. You don't need a preprogrammed PIC to use it. You will need a form of ICD2 to use it properly like the inchworm (has the 5V power supply many ebay clones don't) or mr Stoltzs ICD2 clone which the inchworm is based on.

http://www.hammondmfg.com/dwg2c.htm

Well I've updated the Firefly (RevD) See the details on my site (updates)

Added IR IN & OUT and a TL431 vref option.

Contest open till I finalize the design & PCB (about 2 weeks)

Nice work Bill. One could use there TV remote control to run their computer/X10 via the serial port. First thing that came to mind. And many other things.

Bill, I like the design too. One suggestion, which may just be my personal preference and not widely shared, would be to make the IR emitter on RB3 socketed or at least easily disabled with a jumper, as you have for the TSOP detector. In the applications I have worked on, it was an advantage to be able to move and/or to substitute different emitters. Also, the IR emitter/detector combination you show is so sensitive, it's easier to unplug the emitter than cover with black tape. Last, and maybe most important, if the emitter could be removed, the open socket woud give the user access to a fairly high current switch. John