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Picaxe 28A only works on board

Hi guys. This is very strange, really. And since it is very strange i must have forgot to do something very simple....

 Anyways this is my problem: i got a 28A picaxe, programmed to do a "high 5, low 4". That's all. I connect my picaxe chip on my 28 pin board (the one i also use for my picaxe 28x1) and everything works fine (LED lights up). I take it out, put it in my custom board, and it doesn't work. Now, my "custom board" is not more than a 28 pin IC-socket which has every pin connected to a male header and the download circuit, the battery is connected directly to the V+ pin and so is the ground(V0 pin just under it). This is quite strange.... don't ask me if i have checked the connections, i checked them ten times already!

Have any ideas? 

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no i was talking about capacitors with crystals

@ jka: thanks for the link! but i wasn't afraid not to find it on the net, but at my local electronics store :) anyways it has a nice schematic with capacitors too, thank you :) 

Check http://www.hvwtech.com/products_view.asp?ProductID=321. As for values, it depends on the crystal and you should check the spec sheet for the crystal. I have seen values from 10-22pF being used. Remember to mount the caps and crystal close to the chip.

You'll definately need a crystal or resonator, as others have said, due to the need for a basic clock or "heartbeat" for the chip.  Every instruction fetch and execute cycle depends on the clock. In other words, the clock controls the timing of the execution of every instruction, and without it nothing happens.  Using a crystal is a little more expensive than a resonator, but also gives a more accurate clock frequency.

As for crystals, if you fit one of those, the middle pin of the three (ground) is unused.  But you will need to fit the two capacitors.  Just connect the crystal's two pins to the PIC's pins 9 and 10, then connect two capacitors from ground, one to each crystal pin.

i knew it was some sort of clock, only thought he would need it in some precise commands :)

well thank you everyone for the informations!

oh maybe one last thing: crystals only have 2 pins, so in case i don't find a 3-pin resonators, do you know if there's anyway to get two of them and combine them?

I don't really know how they are made, but i guess you just stick them to the two resonators pin, and the other pin on both goes to the ground.

 Oh and yet another thing :), in case i use crystal will i also have to use capacitors (heard that the resonator soldered on the picaxe have them built-in)? 

i don't know too much about crystals, but if you can't find a resonator, (try farnell) then 3 1/4in floppy drives had a 4MHz on inside of them, and seeing as nothing seems to come on disk anymore, you may be able to find one laying around from an old pc that nooone will miss. (they also have a stepper motor and some other bits and pieces inside too)
ok....i didn't know the resonator would help in switching on and off (high/low) a pin, i only thought i would need it for, say, serial comunication and other time-based stuff. Could somebody explain why they are important even in these actions (switching on/off). It's not for making the picaxe work, it's just because i like to understand how these things work :)

Uh... in my most humble opinion, resonators are pretty much like a heartbeat... you can't live without them. Something need to be ticking inside your processor, telling the circuits it's time to go from one state to another: "hey buddy, it's time to move to the next step in your program." So, my understanding is, that's the role of a clock in any computing device.

I'm not sure what exactly the resonator does though... the gut feeling is, it's part of the clock circuit, isn't it? :)

 

I've got feeling I'm either talking nonsense or something vey trivial... nevermind... :)

(And, uh, sorry if my English is not perfect.)

yeah, a 4MHz resonator, it connects to pins 9 and 10 and the center pin connects to the ground

28_pin_board.jpg

the picaxe manuals have more information on the constructon of boards and so on

hope that helps some...

 also that 4k7Ω resistor is important, too

forgot to mention that the download circuit i built only works with my other chip, the 28x1. To get the program on the 28A i had to plug it onto the board


just an idea: is the resonator needed? i discovered that 28A doesn't have an internal one.