Some questions (Chips, Internal OSC, PCB Designs)

[ccates]

Been lurking and reading for a while and I have some questions that I would like to respectfully submit for answers.

1. What PIC micros can be used in place of the 16F688?
How about 16F88? I've seen some schematics that use this number. Is it a typo on the schematic??
On Phil's blog he mentions a 12F629 project and a 16F627A project.
Will the code work with the 16F627A as is?

Has anybody ever tried a 40 pin PIC like a 16F747? It seems to me like you could get 32 channels from one chip if the code was modded.

I've got 16F627A's, 16F628A's, 16F88's and 16F747's laying around that I can play with. But I don't have any 16F688's.

2. It seems to say in one of Phil's blog entries that if you use the internal oscillator that you are limited to 19,200 baud giving you a maximum of 152 channels. That's plenty for me. Is there just a single line in the code to change to do away with the XTAL? Or do you just change the settings for osc to INTRC_IO in the programmer?

3. Is there a board design for the 8 or 16 channel Renard available that I can make on my own like there is for the SSRs? Or are these designs proprietary? I'd like to have some thing I can print out and use with PNP blue. I don't have anything against COOP's but I teach at a technical college and I think this would make a cool class project.

Thanks !

[Matt]

1. For the current design, you need to use a 16F688. However, there have been other projects using different PICs. For 32 channels off of one PIC, see the "Firegod" forum. The other projects I don't think have been formally published.

2. I'm not really sure. However, the current board designs all have spaces for oscillators, and they don't really cost much.

3. If you consult with the designers (P. Short for the Renard8 or xmus for the Renard16) they may be able to help you, but that is up to their discretion.

-Matt

[ErnieHorning]

At the top of the page, check out the ChristmasWiki. All of the Renard stuff is in ‘Electronics Hardware’, ‘Renard Main Page’. The Renard design starts out as an 8 channel controller and to add more channels, we just chain more 8 channel controllers together. This can be done on the same board or separate ones.

The Renard software should be able to run on most of the PIC’s. The main criterion is that it needs to have a UART and enough memory to hold the code; you may need to change the code to use different pin names though.

The PIC16F688 is running at 8 MHz without a crystal. Some PIC’s can only run up to 4MHz internally and may not be able to run at a consistent rate at that clock speed.

I didn’t use an external crystal last year and I’m not intending to do so this year either. When you can’t add any more channels to the chain, just add another serial port. With USB, you can add up to 32 serial ports. That’s got to be enough, well at least this year. :D

[P. Short]

The reference to 16F88 was indeed a typo. It shouldn't be too hard to modify the code for use with a 16F627A, but changing it for the other parts will not be so easy.

I don't know what PNP blue is, but I have no real issue with making design files for the Renard8 available. It's a two-layer board with relatively fine lines (.010, if I recall right). So it may not that easy for you to deal with. Also, it's in the process of being modified now.

--

Phil

[ccates]

Thanks for the answers guys.

I have three really sharp high school students for a 1 hour study hall 3 days a week. They are kind of bored right now so I thought I would do something interesting with them. I have access to a lot of regular parts and tools so I thought this would be fun. I don't have much of a budget but I can probably squeeze out a few bucks for the parts I don't have lying around. I think it would be fun for them to make their own 8 channel and be able to take it home to use so I'm trying to keep the cost as low as possible. That's why I wish I could use my stock PICS and leave off the oscillator.

Phil I think your design might be a little tricky for this. I was going to use PNP Blue to make a single sided board if possible. PNP blue is a laser printer / iron on resist sheet for making pc boards. A double sided board would probably be too hard for the students. Thanks for the offer though. I think I saw a stripboard design somewhere and that may work out ok. If all else fails I can use wire wrap.

Ernie, What did you do to enable the internal oscillator?

Thanks again!

[P. Short]

The original code did not need the external oscillator. It was changed to allow higher standard baudrates for communications, which required the use of an external oscillator. It only takes a few lines change to the current code to make it use the internal oscillator.

--

Phil

[ccates]

Phil,
In another entry you said
1
"There is already a DEFINE for baudrate, as well as one for the clockrate.
Changing the clock source takes a one line change, I think, in the __CONFIG statement."

I think the config lines you mentioned are :
__CONFIG _FCMEN_OFF & _IESO_OFF & _BOD_OFF & _CPD_OFF & _CP_OFF & _MCLRE_OFF & _PWRTE_ON & _WDT_OFF & _EC_OSC

and

;;__CONFIG _FCMEN_OFF & _IESO_OFF & _BOD_OFF & _CPD_OFF & _CP_OFF & _MCLRE_OFF & _PWRTE_ON & _WDT_OFF & _INTOSCIO

I'm guessing I should comment out the first and uncomment the second?

and change the define lines from

#define CLOCKRATE 18432000
#define BAUDRATE 57600

to

#define CLOCKRATE 8000000
#define BAUDRATE 19200

Will that do it?

[JetMech]

... I think I saw a stripboard design somewhere and that may work out ok...


I don't know if this will help of not. This is the latest stripboard layout I made, months ago,... and I don't think I had anyone look it over and I haven't built it. (hint, hint) :wink:

John

[P. Short]

Those are the lines that I had in mind.

--

Phil

[ccates]

Thanks Phil. I'm gonna order some 16F688s and give it a try.

Jetmech - That looks interesting. I may be able to give it a try. Thanks.

I'll let you guys know how it turns out.

[DynamoBen]

David F created a 24 channel dimmer with a 16F877. Its is run via DMX instead of serial. There is a thread in the DMX section about it. He has a link in his sig to his personal website where it talks about the dimmer in detail.

[PClay]

JetMech.. where is a good source for the stripboards
thanks Phil C

[P. Short]

http://futurlec.com

--

Phil

[JetMech]

JetMech.. where is a good source for the stripboards
thanks Phil C

I used the "Stripboard - Large" from Futurlec http://www.futurlec.com/ProtoBoards.shtml @ $1.95 ea, I think shipping was about $4 for ten.

John

[cmurray]

Ill toss out my design.
A Renard 16 with the bare minimum of parts all point to point soldered.
http://www.christmasinshirley.com/forum/album_pic.php?pic_id=78

Six of these babies equal another 96 channels and ZERO cold joints.

Joel