Chip Connection Failed

Jonb

I am getting an error message while trying to program a SX28 on a custom board. The message I receive is "chip connection failed". The board should work but does not. What possible reasons would there be for receiving this message(I did not use sleep).

I based the programming part of the circuit on the attached image. The only difference·being that I added a 10k resistor from MCLR to Source like on the sx tech board.

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Post Edited (Jonb) : 4/16/2005 7:59:33 AM GMT

KenM

Have you read the voltage Vdd to Vss as you try to program it?

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Jonb

Do you think the voltage is dropping when I program? Perhaps the capacitors hooked up to the power regulator·are inapropriate. On the tech board there is a 10uf cap which I am not using, as I followed the spec sheet for the LM2937 which suggests a .01uf and .1uf cap. I will try to replace the .01uf cap with a 10uf cap and see if it helps.

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Post Edited (Jonb) : 4/16/2005 4:37:47 PM GMT

Forrest

FYI the SX Tech board also has a 0.1uF capacitor (C3) between the Vdd and Vss conections - placed right next to the processor. I think it's important to keep this capacitor as close to the SX processor as possible.

Jonb

Ya I got that one in place. Thanks.

Replaced the capacitor to be inline with the tech board, still no luck... What Am I missing

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Post Edited (Jonb) : 4/16/2005 5:05:09 PM GMT

Bean

Is there anything else connected to OSC1 or OSC2 ?
Bean.

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"SX-Video Display Module" Available Now.

www.sxvm.com

"A problem well defined, is a problem·half solved."
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pjv

Hi Jon;

Are you absolutely sure your supply is a SOLID 5V? You indicate it is 5 Volts, but is that with a scope or a meter?

Only a scope can tell you whether or not there is a glitch on the line; even a short (few millisecond) dip on the power line will upset the Key.

A meter can only tell you if the DC level of the power is bad; it cant tell you that there are no glitches.

Peter (pjv)

KenM

Jon,

Not related to your post but, what pcb layout software are you using?

Jonb

ExpressPCB, because its free. I then polish the art in photoshop,
although I am learning Cadsoft Eagle to get the gerber files.

Peter: I do not have a scope.

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Post Edited (Jonb) : 4/16/2005 7:20:03 PM GMT

Bean

Looks like you have a resonator connected to osc1 and osc2, but that shouldn't prevent you from programming.
Usually the causes are:

Not a stable 5V supply
MCLR not held high
Something connected to OSC1 or OSC2
SX-KEY plugged in backwards

The only other thing I can suggest is if you look at my sx-video schematic, I made 50 of these and every one is programmed on the board.
Bean.

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"SX-Video Display Module" Available Now.

www.sxvm.com

"A problem well defined, is a problem·half solved."


Post Edited (Bean) : 4/16/2005 6:19:36 PM GMT

Jonb

^^ that helped alot, I spotted a problem, I am connecting VSS to pin 3 instead of pin 4. Stupid mistake·· I need sleep i guess.

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Post Edited (Jonb) : 4/16/2005 6:51:02 PM GMT

Bean

That shouldn't be too hard to fix. Pin 3 is listed as No Connection (I don't know if that mean no connection INSIDE the chip, or that YOU shouldn't connect anything to that pin).
But a little jumper should fix you right up. Let us know if that fixes the program.
Bean.

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
"SX-Video Display Module" Available Now.

www.sxvm.com

"A problem well defined, is a problem·half solved."
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Jonb

I cut the trace with a hobby blade, and placed a small piece of stripped wire to pin 4.

As I stare at the mess around me, I thank you all for helping me analyse my problem. The power source which you guys kept stressing panned out. Now that the first is over and done, I look forward to making thousands of boards


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Post Edited (Jonb) : 4/17/2005 2:22:11 AM GMT