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sudhanshu
08-01-2005, 05:02 PM
i have bought pic16c57c-20/p interpretor ic from you, i am working on the homework board and connected the circuit as given by you. As a result my loopback and echo test are successfull, but basic stamp is not found. also i am using resonator 20 mhz which is of only two lega so i grounded the two with 30pf capacitors, and i have got lm7805 instead of lm2940 but giving an output of 5.85 volts. please help!! what should i do.....?

allanlane5
08-01-2005, 09:18 PM
If you've wired in the 7805 it should be giving you 5 volts output, plus or minus like .02 volts. 5.85 is way high.

The two tests you refer to will pass whether the PIC is powered or not. It's only the last one that requires the PIC to be operating. Thus I conclude the PIC is probably not operating yet.

Chris Savage
08-01-2005, 10:45 PM
Hello,

·· Are you saying you connected a PIC, resonator and EEPROM to the Homework Board?· How are you connecting to the serial port?·

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Chris Savage
Parallax Tech Support
csavage@parallax.com (mailto:csavage@parallax.com)

varun
08-02-2005, 04:00 AM
No, what I am doing is the following.
I have used the schematic of the homework board to make my own PBASIC2/DIP based board.

The changes I have done from the homework board are the following:

1. I use the DIP package, so I have mapped the pin numbering according to it.

2. I use a 7805 regulator for more current capacity.

3. The crystal I use have two legs. I use starting capacitors around it to make it working.

4. I use discrete BJTs instead of chips.

When I use the Basic Stamp Editor, I do get a Loop Back AND Echo, but the I get is no Basic Stamp found on detection.

Why isnt my circuit working?

thanks
Varun
aggarwal_varun@hotmail.com (mailto:aggarwal_varun@hotmail.com)

Chris Savage
08-02-2005, 04:22 AM
Okay,

·· So, all the other components, including the EEPROM are the same as the Homework Board?·

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Chris Savage
Parallax Tech Support
csavage@parallax.com (mailto:csavage@parallax.com)

pBASIC
08-02-2005, 12:27 PM
Dang that is 1 nice diagram what program did you use for it pm me

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Chris

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Age

12

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grade

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Webpage (http://members.cox.net/miniwarrior/)
Email=miniwarrior@cox.net (mailto:Email=miniwarrior@cox.net)

varun
08-02-2005, 01:35 PM
Yes, all others·are exactly same.

--Varun

·

Chris Savage
08-02-2005, 10:25 PM
Varun,

·· Not sure why you're trying to copy the Homework Board from a BS2 OEM schematic, but since the schematic you posted uses all through-hole parts, it would seem to be the way to go.· The regulator shouldn't have anything to do with this, although you didn't say if you found out why you were getting such a high voltage reading before.· Possible damage to chips after that?· Could be the crystal...Many chips are touchy about exactly what type of crystal/resonator they have connected to them.· DS1302 is a good example of that.

·· I guess if you're using all the parts in the schematic above (Except the crystal) I would check your wiring.· Are you using the same transistors and resistor values as in the OEM schematic above?· It's really hard to say with home-brew circuits.· Without using the exact parts listed, there's any number of possibilities.·


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Chris Savage
Parallax Tech Support
csavage@parallax.com (mailto:csavage@parallax.com)

varun
08-03-2005, 12:09 AM
Hi

Basically I wanted to make my own board using PBASIC2 DIP package chip. So I first thought I can use the schematic of the homework board.

However I realised that the Homework board using the surface mount chip which has different ordering of port pins.

Thus I went for the BS2 OEM schematic, which uses a DIP package. However I dont have a brownout detector as placed in the BS2 OEM schematic. Thus I thought to use the HW board schematic which doesnt require a brown out detector.

If I am not wrong the HW board and the OEM schematic are exactly same except the difference in pin ordering and brown out detector being replaced with a push button circuitry.

Now, that is the saga of making a choice in schematics!!!

Maybe I have damaged my PBASIC2 already and I will try a new chip to see if it works... I dont want to destroy the second one as well.... :((

Any hints will be useful.

Thanks

Varun

Chris Savage
08-03-2005, 12:28 AM
Varun,

·· The brownout detector is certainly not required.· Of course, I have seen various people on the forums take several different approaches to removing things they don't want.· In a few situations it was easy to pinpoint in they ExpressPCB layout, or in one case a picture of the built circuit on a breadboard.· But remotely it's hard to tell.· But always verify your power source before connecting anything sensitive to it.

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Chris Savage
Parallax Tech Support
csavage@parallax.com (mailto:csavage@parallax.com)

sudhanshu
08-03-2005, 04:18 AM
In the pic datasheet i found that capacitors with which oscillator is grounded vary with different oscillators. A crystal oscillator uses 22pf capacitors for ground,whereas ceramic capacitors need 30pf capacitors for ground.mine is crystal ie. hc-49/us so i will try changing the capacitor values.

varun
08-04-2005, 02:21 AM
my circuit works!!

thanks
VArun