P16PR0 schematic discrepancy

[markdguzman]

Hi there y'all. I'm a noob to pic programming and would really want your patience on this matter that I have regarding the p16pro programmer that I have built. There have been several conflicting schematics, as I've found out after etching and soldering all the components in, with the resister labelled as r11 (680r) / r9 (same value). My main thrust is to be able to build a digital clock using a seven segment led with alarm/date capabilities with the pic16f628a as its brains. In the pcb that I etched I noticed that there was no placement for the componenet r11, hence, as you can see from the image I soldered it from the backside of the pcb. Is my programmer ok based from the images I provided? Hoping for your kind and much needed input on this matter. Much obliged.

 

[eblc1388]

Of course there are different versions of the schematic, because people like to change things a bit. But it really doesn't matter.

The important point here is which schematic you have chosen to use. How would we know without looking at the specific schematic that you use?

You need to post the schematic in GIF file format, or a link to it.

 

[markdguzman]

MENTAL RELAPSE

Sorry, but here is the schematic and pcb layout that has the r11 placement missing.

 

[eblc1388]

Good. I see your problem now.

The R11 is a resistor added after the PCB is built and people experienced difficulties in the PIC not entering the programming mode. R11 is just to pull down on the MCLR line before Vpp is applied.

You are perfectly OK to just solder it on the back of the PCB.

 

[Nigel Goodwin]

Good. I see your problem now.

The R11 is a resistor added after the PCB is built and people experienced difficulties in the PIC not entering the programming mode. R11 is just to pull down on the MCLR line before Vpp is applied.

You are perfectly OK to just solder it on the back of the PCB.

I would agree, although it's strange that there's a pull-down on the Vpp rail, and NOT the Vpp40 rail as well?.

I've never seen one without R11 on the board though?, so it must be a VERY! old PCB design - certainly the DIY Electronics board has it fitted correctly (between T1 and the Program LED).

 

[markdguzman]

Many thanks!

Whew, that was fast! Thank you so much to both of you! Now I just hope I'm headed in the right direction with my choice of pic, 16f628a, in building and eventually mass producing on a medium scale led clocks.

 

[Nigel Goodwin]

Re: Many thanks!

Whew, that was fast! Thank you so much to both of you! Now I just hope I'm headed in the right direction with my choice of pic, 16f628a, in building and eventually mass producing on a medium scale led clocks.

It's a good general purpose PIC, but does it have enough I/O pins?.

If you use a crystal oscillator (as you need to for accuracy), that leaves 14 I/O pins, 7 + 4 for multiplexing your four 7 segment displays, which leaves three spare. One for an alarm output leaves two for clock setting, which is getting a little tight on pins?.

However, by clever design you can use some pins for more than one purpose, you might try consulting the old MicroChip application notes for clocks for ideas?.

 

[Mike - K8LH]

I believe one or more of the Microchip Clock application notes Nigel refers to may multiplex switch inputs on segment drive lines...

And if you're using discrete 7-segment displays instead of a single multiplexed 4-digit display, you can always use Charlieplexing to drive the displays using 8 pins (no decimal point) or 9 pins (decimal point)...

Regards, Mike

 

[markdguzman]

Hmmm...

Well, will be able to comprehend the looming pin shortage soon I'm really new at this, microcontrollers, I am a writer by day and an electronic/electrical enthusiast by night or any spare time that I have I just got so fascinated by led clocks and was turned off by the price here in the Philippines. So I vowed to myself that I'd just make one and it led (no pun intended) me to PIC Thanks, Nigel, for the concern. I hope that you'd be able to help me when I get down to the dirty deed of making it work already I just finished building my programmer today and will test it soon. Wish me luck! Thank you again!

 

[markdguzman]

Charlie...

Thanks, Mike! I guess I'd have to get myself acquianted with Charlie soon I have no idfea which led to use yet. Will get to nag you guys soon as I burn my first proggie Will start with Nigels tutorials soon as I test my programmer.