Soft-RS232 on 12F675 ~ Not syncning? - Page 2 - Electronic Circuits Projects Diagrams Free

jess · 3rd February 2007, 06:04 AM

I just discovered the 12F683 chip some time ago. It can operate up to 8MHz and does not use an OSCAL value. It is somehow self calibrating. I'm using it now instead of the 12F675. Check it out.

Jess

Mike, K8LH · 3rd February 2007, 01:44 PM

That's my favorite 8-pin PIC. I should have mentioned it to you before.

It's fast enough to support a full-duplex 9600 baud bit-banged serial I/O package with circular buffers using 3x bit-rate interrupts.

Regards, Mike

donniedj · 3rd February 2007, 05:42 PM

I have alot of samples of both 675 and 683 (683 collecting dust in bin) but was unaware that 683 default calibration value '0' means factory calibration. All this time I thought all 8-pin PICs must be calibrated once erased just because the 675 must be.

These 8-pin and 8-bit wonders just keep getting better. Only if the other Micro company could follow in Microchips footsteps, only if...

eng1 · 3rd February 2007, 06:00 PM

The calibration values are stored in fuses in a special register, beyond the user program memory and they're not erased when programming the PIC12F683.
I like this PIC because it has TIMER2 module too.

Mike, K8LH · 3rd February 2007, 06:21 PM

It's also the only 8-pin part with a CCP module.

Please check out this zero jitter 8-channel Servo Controller concept (below).

Regards, Mike

Mike, K8LH · 3rd February 2007, 06:24 PM

The PWM module is pretty cool too, though the example RGB Accent Light Controller below uses software PWM;

Mike

divya sebastian · 9th May 2008, 10:35 AM

hi!
this is divya sebastian here.
i am first year electronics student. now i shall explain the depth of my pathetic situation.i have leant no computer languages before...

.and as a result i am in deep trouble when it comes to PIC . now i have been given a project , the jist pf which is as follows.

'' you are to design code debugg and demonstrate a system which shall enable the following mesage to be sent to a pc oer an rs- 232 connection

the message to be sent shall be ' ABC' ''

SO IS THERE ANY KIND SOUL OUT THERE WHO CAN HELP ME SORT THE WHOLE THING OUT... N TRY N MK ME UNDERSTAND THE WHOLE PIC thing.

well we r supposed to use a pic 12f675.

pls do mail me at divyasebastiank@yahoo.com

thanksssssssssss

Quote:

Originally Posted by johankj

Hello all. This is my first post, althought I've been reading this forum quite a bit. Excellent stuff! Anyways, I hope there is someone out there that can help me with my little PIC-Chip.

I'm a novice with PICs, but I have a good project which require RS232. I have managed to to it with a 16F627, but I need ADC on a small footsprint, so I went for the 12F675.

After I rewrote the code to fit the 12F675, I just couldn't get it working.

I was banging my head against the wall for weeks, but I just couldn't figure out why.

My suspicion is that I overwrote the OSCCAL values. I'm not sure if I can read the location of that value, since the programmer I'm using (Velleman) is not that good. If I jump to that address, as part of the recommended calibrarion routine, the PIC hangs. I'm pretty sure it's lost, is this what you would expect from an overwritten OSCCAL value? 3F3F, I'm not even sure what that transelates to in Opcode. I've ordered a proper programmer, which should arrive next week

BTW: Two good links to pages regarding OSCCAL:
http://users.tpg.com.au/btkelly/pic/osccal_sync.html
http://www.petesworld.demon.co.uk/ho...PIC/piccal.htm

I'll post my code below for anyone to check. Sorry for the mess, couldn't get the table thing to work. I've written it as simple as possible, with no trixi parts. Is my code ok? Does it do what I want it to do? (Which is to output an ASCII letter every now and then

)

I'm gonna order a few more of those 12F675, and see if I can't get it working. Any advice on the above would be most appreciated, to recap: Is my code OK, and have I overwritten OSCCAL?

Does anyone know the aproximate frequency-range for the internal oscilator?

Oh, and the project I'm doing with this particular PIC is a circut that samples temperature and moisture, and sends it down RS232. I will actually use this on work. I'll post the whole project when it's done, if anyones interested.

All replies are most welcome. And thanks again everyone for an excellent forum.

johankj · 9th May 2008, 06:44 PM

I am not going to write the code for you, but I can point you in the right direction:

Nigel Goodwin has some good tutorials for PICs, and he also describes a software based RS232. The 12F675 Doesn't have an inbuilt hardware USART, which would make it easier. You will basically have to write a "software" USART. Look here for Nigels tutorials: http://www.winpicprog.co.uk/pic_tutorial.htm

I will be happy to try to answer any technical questions. Good luck

3rd February 2007, 05:42 PM	#18 (permalink)
donniedj Experienced Member Join Date: Jan 2004 Location: So Cal Posts: 328	I have alot of samples of both 675 and 683 (683 collecting dust in bin) but was unaware that 683 default calibration value '0' means factory calibration. All this time I thought all 8-pin PICs must be calibrated once erased just because the 675 must be. These 8-pin and 8-bit wonders just keep getting better. Only if the other Micro company could follow in Microchips footsteps, only if... __________________ "Code more, post less." - by the ACG, by Me http://www.anothercoilgunsite.com Truth Be Told: http://www.kuro5hin.org/story/2004/2/7/144019/8872 Kits hinder. Oscope and single cycle debug endows you with intimate wisdom and know how.

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3rd February 2007, 06:04 AM	#16 (permalink)
jess New Member Join Date: Nov 2006 Location: Virginia Posts: 28	I just discovered the 12F683 chip some time ago. It can operate up to 8MHz and does not use an OSCAL value. It is somehow self calibrating. I'm using it now instead of the 12F675. Check it out. Jess

3rd February 2007, 01:44 PM	#17 (permalink)
Mike, K8LH Experienced Member Join Date: Jan 2005 Location: Michigan, USA Posts: 1,495	That's my favorite 8-pin PIC. I should have mentioned it to you before. It's fast enough to support a full-duplex 9600 baud bit-banged serial I/O package with circular buffers using 3x bit-rate interrupts. Regards, Mike

3rd February 2007, 06:00 PM	#19 (permalink)
eng1 Experienced Member Join Date: Apr 2006 Location: Italy Posts: 818	The calibration values are stored in fuses in a special register, beyond the user program memory and they're not erased when programming the PIC12F683. I like this PIC because it has TIMER2 module too.

9th May 2008, 06:44 PM	#23 (permalink)
johankj Experienced Member Join Date: Jan 2007 Location: Norway Posts: 110	I am not going to write the code for you, but I can point you in the right direction: Nigel Goodwin has some good tutorials for PICs, and he also describes a software based RS232. The 12F675 Doesn't have an inbuilt hardware USART, which would make it easier. You will basically have to write a "software" USART. Look here for Nigels tutorials: http://www.winpicprog.co.uk/pic_tutorial.htm I will be happy to try to answer any technical questions. Good luck