Yet another PIC14

[Phil__G]

Just to say thank you to whoever it was gave me a PIC14 PCB at the retrofest (was it Simon?) sorry I dont know who it was but thank you, its working great.
I havent fitted any of the serial bits as I'll be using a CH40G USB serial module which will also power it so theres no 7805 etc either. A friend was also interested so I ordered another 5 from JLCPCB, will have a couple of spares if anyone is interested. RS still has DIP 876's but they're a tenner each!
It has my slightly modified software with save-after-hexload and temporary default 'message' - this is fresh off the PICkit2, nothing keyed or hexloaded yet.
Video:
https://youtu.be/J_nfwLZIPh0


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[SiriusHardware]

I have quite a few DIP 876As here as they were used in a product at work until recently. As usual, I salvaged what was left over when the production run ended, so if anyone ever needs one just ask.

[ortek_service]

Originally Posted by Phil__G

>>
RS still has DIP 876's but they're a tenner each!
>>
.

It seems many PIC's are often relatively-expensive for an 8bit uC. With many ARM's (Although it seems STM32's have recently quadrupled in price) and now ESP32's being a lot better value - especially for performance.

Although PIC's & ATMEGA's (also often a bit expensive and recently many non-stocked & 1yr lead-times) are usually better for 5V system's if you don't want to have to add level-translators (Although these can be quite cheap, but many in very-tiny SM packages)

However, there are a few other stockists of the PIC16F876 in DIL, that are a bit cheaper than RS. And if A-suffix versions is OK, then that seems cheaper, Although -04 4MHz one (if suitable) doesn't seem to cost much less than -20 20MHz one.
See here, for price comparisons / current stock (Although I tend to ignore any result from distributors in the Far East you've never heard of, as sceptical whether they really have genuine stocks or will just try to source some and may not be genuine):
https://octopart.com/search?q=pic16f...e_package=PDIP

I'm sure I've also got a few PIC16F876's in DIL around, after previously using these on a project where a few more resources were required than PIC16F84's etc had, and the odd Microchip Demo board for PIC16F87x DIP uC's.

[SiriusHardware]

Ah, that's a point, the 876As I have a stock of may not be the 20MHz flavour, I would have to check that. Although - is it the case that the 'A' versions are all 20MHz? Have to check that too.

[Phil__G]

Karen routinely ran 4Mhz parts at 20Mhz

[SiriusHardware]

Third page of the datasheet here

https://ww1.microchip.com/downloads/...doc/39582b.pdf

says that the 'A' versions are straight-up 20MHz, and those are the only versions I have - so the offer stands, assuming of course that the PIC14 can run OK with the 'A' suffix version?

[Phil__G]

Not tried the 876A but the 877A runs in the 'big' PIC14 so I expect it will be fine

This little board is great but I'm missing the flag outputs already...

[ortek_service]

You would think that the 4MHz rated ones might be exactly the same internally as the full 20MHz rated version, but maybe didn't pass a particularly factory test so they sold them as a down-graded version. But maybe when running at highest voltage, they will still generally be OK (especially just at room temperature). These may also be like ATMEGA's, where although there are low-voltage versions, you can only run at max speed towards 5V Vcc.
Maybe later ones were all OK, and they just sold some under lower-speed part number for legacy reasons to those still ordering that being as price seemed the same for both.
It might also be the case that both are to be discontinued, if the 'A' suffix version (which seems to be being sold cheaper) will effectively replace both speeds of the original versions (Although might be a problem, if some software changes are actually required)

From discussions here, it seems the main issue with changing to 'A' suffix versions is that extra Comparators maybe on by default and might need to be disabled:
https://www.microchip.com/forums/m32870.aspx
https://www.microchip.com/forums/m299069.aspx

But there are also some ICSP & Program space writes differences, with full details of differences in the Microchip PIC16F87x to PIC16F87xA migration document here: http://ww1.microchip.com/downloads/e...Doc/39591a.pdf

There shouldn't be any problems using the 'A' hardware-wise, and if the PIC16F877A worked OK then software is probably compatible (Although maybe lower pin-count 876(A) might be more likely to have some issues than 877(A)) . But could probably re-compile for 'A' version, after disabling comparators etc if required.


If the 876(A) version of PIC14 lacks Flags etc I/O, then presumably these could be restored with some external port expanders like some Serial to Parallel shift registers (74HC595's seem to have been recommended for driving LED arrays on standard Arduino's) and appropriate software mods to support this.

[Phil__G]

By far the easiest way is to try an 876A. Karens code doesnt use the comparator or any timers and IIRC disabling them is only a power saving option. I think it will be fine.
Re flags, its really not worth the trouble of expanders and code changes - I do have a 'big' PIC14 too but the easiest and neatest 'conversion' of the small one would be to make a 28-pin dip carrier with a QFP 877. It would be just as quick and easy to build the big one! (or a PICL ! )
It is what it is, I think its fine
In fact its a "Jolly fine buy"

https://youtu.be/J_nfwLZIPh0

[Phil__G]

PIC14 PCBs have arrived from JLC, thats 15 days using the cheapest 'not recommended' shipping option. These are from Simon Merrifield's gerbers in blue, I like them better than the black ones. I'll keep a spare, I gave one to Wiggles, so there are two up for grabs

[Phil__G]

These boards from Simon's gerbers are really nice and make a really neat PIC14
Wiggles wanted to copy my USB mod so I wrote it up, its a PDF at the bottom of the PIC14 page on philg.uk just below the code update for saving hexloaded programs.
Cheers
Phil

[Slothie]

I'm pretty sure when I made my PIC14 from Philipou's schematic I tried both the 877 and 877A at some point (although that was a while ago....). From my experience with the Ortonview, it should be fairly trivial to get a 887 to work, you just have to zero a few registers on reset to disable unwanted devices to make the I/O the same as the earlier device. The 887 is about £3 on eBay and doubtless much cheaper from regular sources.

[Phil__G]

Re the use of an 876A in the mini-PIC14, Tony used an 877A in his PICLv2 without any code changes at all
https://www.vintage-radio.net/forum/...30#post1439530
Sirius if you want to send one I could try it right away & report back?
Re the 887, cant remember if I've used that one before... I did use a few 18877's with Mikes code... all good
Cheers
Phil

[Slothie]

Originally Posted by Phil__G

Re the use of an 876A in the mini-PIC14, Tony used an 877A in his PICLv2 without any code changes at all
https://www.vintage-radio.net/forum/...30#post1439530
Sirius if you want to send one I could try it right away & report back?
Re the 887, cant remember if I've used that one before... I did use a few 18877's with Mikes code... all good
Cheers
Phil

When I was looking around the project folders on my laptop for the PIC14 stuff I saw there was a 18877 data sheet in there so I must have investigated it. I think I was looking for a replacement for the old 877 as at one point they were unobtainable unless you wanted to spend a lot at LittleDiode

Microchip made many apparently pin compatible devices so I'm sure there are plenty of options available if you change the reset to initialize it properly. I noticed the 18877 could be clocked at 32MHz which offers a potential speed upgrade . I think I was also semi-seriously considering if it might be possible to combine Karens PIC14 SC/MP core with the Ortenview code and make a combo unit, as I had jokingly said to her once, hence the faster PIC, although if I was to even consider that I might go to the PIC18 series (also a number of "pin compatibles" although I imagine you'd need a higher pin count device) because of their greater clock speed and general efficiency.

Seems like there is still a lot of possibilities with Karens legacy.

[SiriusHardware]

Phil, certainly will send you some 876A, there is a newer pin compatible equivalent, the PIC16F886, but that would probably need a bit of code modification to turn off the analogue inputs and make them digital I/O pins instead. I'm back at work early next year, will dig out some 876A then.

[Phil__G]

Thanks G, one will do, its just to confirm the 876A does work in the mini-PIC14 as we all expect it will

Also a bump to say that I have a couple of Simon Merrifield's PIC14 pcbs needing a home FoC...

[SiriusHardware]

I'll send you a handful if I can find them as you seem to be the head cheerleader for the PIC14 project these days - anyone who needs a chip is more likely to encounter you, rather than me, first.

[Phil__G]

I dont know about that G but assuming they work ok which I'm almost certain they will,
for anyone wanting to join in the fun we will have two PCBs each with a programmed 876A chip up for grabs FoC

[Michael - K8LH]

Gosh, that's a nice looking little PCB, Phil. Is that a ULN2803 replacing the 8 transistors? Is there a schematic and Gerbers available somewhere?

Happy Holidays and cheerful regards, Mike, K8LH

[Phil__G]

Here you go Mike:
https://oshwlab.com/g7sfi/pic14-v2/