My chip is ignoring my PC

[The Master]

Hi. Sorry to bother you all once again but im having more trouble with my circuit. Im using a MAX232 chip to connect a PC serial port to a PIC16F627. The data isnt getting to my PIC. Ive checked all the connections and they are all ok. Ive checked the pinouts and they are all correct. My PIC chip does work. It runs a startup sequence then waits for a serial input but it doesnt get there.

This all worked perfect on a breadboard the other day but now its the real PCB. Can anyone think of any common problems in this kind of setup that i might not have checked? Is there anything can give you to help you help me? (Schematic not available but i do have the PCB layout)

[mister_e]

better than nothing i guess.. post it and also post your code and .HEX file

[The Master]

Ok. The PCB looks a bit crowded so it might be hard to look at. Some components are under the PCB thats why they seem to overlap.

The code isnt the final version but it worked perfect on the breadboard tests

[Norbac]

Hi, the easiest way to verify to circuit (at least the max232 part) is to put a jumper between tx and rx pins (ttl section), so everything you write down to the PIC will be send it back to the computer, remember this is just to verify the max232 part. For the PIC section you must write a little code to turn on and off a pin every time the PIC receive a message from PC. At least this is what I do every time I want to be sure my hardware works correctly.

Regards

[mister_e]

Your .HEX says that you're using a XT osc... but your code says... DEFINE OSC 16... it has to be HS

MCLR is enable.. not sure you handle it on your PCB or if you're using it as i/o in your program.. not seen in your program 'till now...

Now you see some advantage to set the fuses in your code?

[The Master]

I have to set the fuses in my programmer. I do set them to what you said.

Anywho. I found the problem. I tried linking the serial output directly into the serial input (NO circuits at all) and it didnt work. Aparently ive blown my USB<>Serial adapter up earlier when my circuit started smoking. Ive tested it in a standard serial port and its working :D

Sorry to have bothered you but thanx for the output>input idea. Cant believe i didnt think of that before

[The Master]

Ive just done some checks and yesterday i successfully blew up:-

1 X MAX232 chip
2 X 1K Resistors (violently)
2 X PIC chips
1 X Tri-color LED
2 X Diodes
1 X USB<>Serial adapter

Not a bad day!

Im making 2 circuits and the other one is now working perfectly. Nothing has blown up yet. I did happen to order spare PIC chips, LEDs etc and i got boxes of 1000 resistors so that all ok but the Maplin store near me only stocks 2 of the MAX232 chips at a time and wont get anymore in till Jan :(

Does anyone have any interesting ways of removing a chip from a PCB? Unfortunately i didnt have any DIL sockets that fit the MAX232 so now i have to remove it. Anyone have a good way of getting chips out?

[mister_e]

There's almost nothing a good hammer couldn't remove :D

Is this a 2 layer typ (cop. on both side) or single?

Usually, a mix of desoldering pump and clean solder wick do the job.

EDIT: nice google... http://www.epemag.wimborne.co.uk/desolderpix.htm

[mackrackit]

Does anyone have any interesting ways of removing a chip from a PCB? Unfortunately i didnt have any DIL sockets that fit the MAX232 so now i have to remove it. Anyone have a good way of getting chips out?

Solder Wick.
Heat the connection and use compressed air to blow the solder away.
Hot air gun.

Wire cutters:)

[T.Jackson]

Heat the connection and use compressed air to blow the solder away.


That sounds very dangerous.

[The Master]

Heat the connection and use compressed air to blow the solder away.

Sounds like fun :D

I dont have a desoldering tool. Ill have a look for one when i go to the Maplin in Nottingham. Not sure where i would get compressed air from but i think i could put something together. Other than that i look like cutting the pins off the chip with a stanley knife and desoldering them 1 at a time.

Im gonna see if Maplin have some DIL sockets too and hopefully when i turn it on again it wont start smoking.

Thanx for the suggestions

[T.Jackson]

http://www.dse.com.au/cgi-bin/dse.storefront/475a9b4601c906d82740c0a87f9c06ad/Product/View/T2270
is a good buy if you can afford it. Not quite like a Hako, but it's a quarter of the price though. Worth the money, especially if you're considering doing something stupid like; heating up a large solder joint and then using a high-powered air compressor to blow it away, standing a good chance of causing somebody some injury. Cheap for $299, might save your eyesight!

[Melanie]

but the Maplin store near me only stocks 2 of the MAX232 chips at a time and wont get anymore in till Jan

Tell me you're not seriously paying Maplin (prices from their website) £2.28 (or even £5.27 - hey that's US$11) !!!!!!!!

If I sold them at 50p each I'd be making 250%... time you looked around for a better components supplier...

[The Master]

That desoldering station is very expensive. I wouldnt use it all that often either.

I do have eye protection and i wouldnt blow hot solder at myself. Ive had it hit me in the face before and its not good.

I usually buy my components from Rapid Electronics but they dont have a store within 50 miles of me and im not travelling that far for 1 chip. Would cost more in petrol. I could have it delivered but it wouldnt get it till Jan

[T.Jackson]

That desoldering station is very expensive. I wouldnt use it all that often either.

I do have eye protection and i wouldnt blow hot solder at myself. Ive had it hit me in the face before and its not good.

I usually buy my components from Rapid Electronics but they don't have a store within 50 miles of me and im not travelling that far for 1 chip. Would cost more in petrol. I could have it delivered but it wouldnt get it till Jan

They're not cheap. But I can say that as far as they go in terms of quality for price -- that DSE desolder station doesn't look half bad. No match for a Hako though. Bout 10yrs ago I bought a top-of-the-line Hako for $1,500. At one stage I put that thing through daily non stop use for about 2yrs repairing wireless nurse call systems. To give you an idea about how much use, everyday I probably replaced about 25 battery snap connectors, trimmer caps, pull cords, BC337 & (similar) transistors, ferrite rods w/ coil, that covers the wall buttons. As for the other stuff, dip switches, M6502 CPU, res nets, gotta have done 1,000 shots a day with that gun.

If you ever come across a cheap Hako, grab it!

[mackrackit]

That sounds very dangerous.
Well I did not mean to use 100 psi.

The solder cools as the air hits it so short burst is enough. One of those "cans O air" works well.

Blowing through a drinking straw will also work. Not much air is needed. As long as you do not hyperventilate.:D

Wait for the solder to just start flowing and apply air.

I use this often, I make many mistakes!

[BobK]

Hi Dave,

Using fine tipped cutters, clip each pin as close to the IC as possible. Then with needle nose pliers holding the clipped end of the pin, heat the solder joint and pull the pin out. You must be carefull when pulling on the pin just in case the pin is bent over on the solder side. I use a solder sucker to remove the excess solder. Sometimes you need to put some more solder on the joint to use a solder sucker or wick but I have found it to a very good method.

HTH,

BobK

[Melanie]

Chop the legs off the chip as close to the body as possible - leaving as much on the PCB as you can to grab in the next stage. A good pair of flush side cutters should accomplish that. One at a time, heat up each joint and with a pair of long-nose plyers pull the pin out through the top (you should have left enough of the pin in the previous step to grab). Use a standard $5 solder sucker with a half-decent nozzle to SUCK the joint clean... digressing (only slightly) - what I don't understand is why it's called a 'Blow Job'... - but I could be on the wrong forum again....

[The Master]

I was thinking about cuttin the legs off. One thing i normally do for small circuits is heat it up then drop it and the solder falls off onto a bit of wood. Thats hard here though because theres more components under the chip. I think cutting it up then blowing the solder off is the best option based on the tools i have