Communications Board Testing

Hi,

after building my "Power Distribution and Communications Board - v1.1", i am trying to test the voltage as described in the section "Debugging your serial connection". But I am getting different values. I have controlled my board, but I cannot find a miswiring or short.

I am using an ATX power supply, which needs a resistor to switch on (this could not be the reason for the different measure, or?). I put the resistor in the power connector for a module. The Power Supply is delivering a voltage of 9,3V (messured at P1). And I am using the variant with the MAX202 (is this the reason?) and with 0.1uF for C2-C5.

The device is not plugged into the PC and the communication connectors are empty.

From the documentation the values should be:
"Pin 15 to 16: 5V. A mismatch suggests a power supply or 7805 issue.
Pin 15 to 14: -7 to -15V. A mismatch suggests a short on the board or a miswiring of the cable.
Pin 15 to 13: 0V. A mismatch suggests a miswired cable.
Pin 15 to 12: 5V
Pin 15 to 11: 4 to 4.5V. "

My measurements are:
Pin 15 (-) to 16 (+): 5,1V
Pin 15 (-) to 14 (+): +6.7V !
PIN 15 to 13: 0V
PIN 15 to 12: 5,09V
PIN 15 to 11: 0V !

Have someone an idea what could be wrong?

thanks
andreas

perhaps you are measuring the voltage backward? the reverse is about -7v. also, are you testing with the chip installed? i think these are supposed to be measured without the chip.

also, it would be helpful if you could post a detailed shot of your board, something might pop out to one of us.

changing the power supply with a battery, which is delivering a current of 11V at P1 and without resistor (which was needed for the ATX power supply). I am getting
-9.5V between Pin 15(-) and 14(+). Between Pin 15 and Pin 11 I am still getting 0V.
Trying the echo test with minicom, everything looks good.
So I will try to get a other power supply.

andreas

hello Zach,

ZachHoeken Wrote:
-------------------------------------------------------
> perhaps you are measuring the voltage backward?
> the reverse is about -7v. also, are you testing
> with the chip installed? i think these are
> supposed to be measured without the chip.
I tried several times in the described direction (Pin 15 (-) to 14 (+)). And the measurements are with the chip installed.
without the chip, I get 0V from Pin 15 to 14, 13,12,11,10,9 and 5V from Pin15 to Pin16.


>
> also, it would be helpful if you could post a
> detailed shot of your board, something might pop
> out to one of us.
sorry, I have no camera here. but I will try to organize one.

andreas

good to hear. thats strange that the power supply wasnt giving you the right voltage, but i'm glad you found the solution. i do know that the powercomms board works and is tested.