50$ robot - reset pin is showing 0V

[ibot]

Hi,

The reset pin [the one connected to AVR programmer] is showing as 0V when I tested with my multimeter. But, when I checked, there is a 5V supply at VCC.

wondering, what I am doing wrong? Does anybody experienced similar situation? Thanks for your help !!

[Soeren]

Hi,

Check wiring and soldering, with a magnifying glass, lots of light, and even more patience.

If problem persists, be more informative in what you have done/measured, where and how it went.

[ibot]

hmm .. checked all the connections. seems everything looks good as per the datasheet. apparently, it still showing 0V on reset pin

I am calculating voltage using a multimeter. It is showing 5 v on VCC pin. So, I connected my programmer header. But, the LED on programmer header is blinking orange .. when I referred to its help pages .. it says, orange blinking is either due to improper connection or no pull up on reset line.

I rechecked the program header connections and that looks good. But, there is 0V on reset line. I put my red probe from multimeter on reset pin and kept the black probe on ground. showing 0V

My assumption is, microcontroller will take care of the voltage on reset line. is it correct? or do we need to connect a wire from output pin of regulator to reset line ?

Thanks !!

[cyberfish]

no pull up on reset line

Add a pull-up (resistor) from reset pin to 5V.

10K would do. Value not really important, just not too low.

[ibot]

Hello,

I saw somewhere that ISP's with older firmware had a similar problem. So, I got the latest patch for this ISP. Now, it is complaining MISO and SCK are short circuited.

Still wondering, what does that mean? any help ?

=====
cyberfish,
I guess you want me to try with 10k resistor between 5v and reset pin .. As, I do not have one readily available, I tried .. the following ..

1. added a 330 ohm resistor and tried .. I saw #'s in 0.7 mv
2. i replaced 330 ohm with a 1.5 K resistor .. it is around 0.1 mv
3. then, I replaced the resistor with a jumper wire .. i was getting upto 13 mv

In all the cases, the connector is still blinking orange

Greatly appreciate any help !! Thanks !!

[cyberfish]

330 ohm is way too small. The ISP may not be able to pull it down.

Use anything above 10k (to 1M).

[Soeren]

Hi,

hmm .. checked all the connections. seems everything looks good as per the datasheet. apparently, it still showing 0V on reset pin

So, not everything is good.
No matter how good it looks, it's not if it don't work. can we agree on that?

You tried the pull up but it didn't help (if 330R won't pull it up, the problem is elsewhere).
You looked at it carefully for at least an hour, through a magnifying glass in plenty of light (i.e. 2,500 Lux at least).
Assuming you didn't overlook anything, there's only one conclusion: Your controller is dead.
(but do look it over one more time before buying another controller).

Remove the controller and mount the 10k+ pull up. Now measure the reset pin (without the controller).
To check connectivity of traces, use the continuity function in your multimeter (or the 200 Ohm resistance range if your meter haven't got continuity test).

Whatever you do to the board that includes soldering, drilling or any kind of electric tools, pop the controller out and place it on a piece of tin foil (that you touch with a finger before you out the chip down). If it ain't dead allready, let's keep it like that.


Btw.
Which board are you using? Something homemade, a breadboard (soldered or solderless) or a kit of some sort?
I get a creepy feeling that it may be a layout error.

My assumption is, microcontroller will take care of the voltage on reset line. is it correct?

No, the microcontroller get told to reset by the voltage on that line.
When low it will keep the controller in reset condition.
(Hence the 10k+ pull up resistor).