Have I blown my Axon II

[Pianigro]

Hi, I have been building a hexapod with 12 servos and a sharp IR distance ranger. I am using AVR and webbbotlib to program the robot.

All was progressing as planned, I have been using a battery pack made up from 6 x 1.5V AA batteries however I keep running out of power. In my wisdom, I connected another battery pack to the unregulated bus and something began to smoke. I quickly disconnected all power and was not sure whether I might have connected a power pack in reverse.

Anyways, now when I connect a battery pack, eg 4 x 1.5v AA batteries, the robot beings to initialise (centering servos, etc) then it goes all haywire and the battery connection gets a little warm. The power led is not its usual bright self.

Any ideas?

Thanks
Paolo

[rbtying]

Use a multimeter to check for continuity between the power and ground rails--it sounds as though you've got a short somewhere, probably in the device that "began to smoke"

[Admin]

rbtying is right, let us know what you find.

It *might* be repairable, so I need to find out exactly what you did . . .

First, 1.5V * 6 cells = 9V. Most servos will fry after 6V. What type of AA - lithium, NiMH, lead-acid, etc?

Assuming that a servo fried, that could be where your short is. Remove all servos and test each individually.

Were both battery packs connected to the unregulated bus, or was one on the regulated? Were both packs exactly the same voltage?

Does the voltage regulator get warm when you power up your Axon?

[Pianigro]

Hi,

Thanks for the reply, sorry I have taken so long to respond, work and Chrissy has taken up too muck of my time.

I checked for shorts - all looked good, it could have been connecting the other battery pack with the polarity reversed which caused the initial problems. I did find a loose connection between my battery pack and the switch that come with the Axon and fixed that. That could have been causing the irregular movement by resetting the Axon whilst in the middle of the walk cycle.

I have now tested my Axon II and I think I have blown my UART. The mini usb port does not work. I use a Pololu Programmer which has an additional serial port to which I connect the UART 0,2 & 3 from the Axon and get no data coming through. Is there any way of repairing the UART?

Re the 9V, I was using normal AA alkaline batteries, I started using 4 AA (6V) but the Axon kept on resetting itself as the voltage was dropping too low. The 9V option worked but I still ran out of power. Now I am using a 6V 1.2A rechargeable battery and all works well. I have posted a new topic today a lab power supply to use while programming my Axon so as to conserve my battery life but having issues - probably bought too cheap a power supply - it is rated at and output of 6V 1.5A but the amps oscillate and my Axon keeps on resetting - grrrrr - but will figure it out.

By the way, voltage regulator is not warm.

Otherwise all else seems to be working.

[Admin]

Is it safe to assume that you've resolved the power issue?

I have now tested my Axon II and I think I have blown my UART. The mini usb port does not work. I use a Pololu Programmer which has an additional serial port to which I connect the UART 0,2 & 3 from the Axon and get no data coming through. Is there any way of repairing the UART?

Did you connect anything to the UART beyond the Pololu/USB cables? Did you plug anything into the 3.3V output pin?

Are you sure you have the right COM and baud rates selected when viewing UART data?

[Pianigro]

Thanks for the reply,

I have resolved the power issue, UART still giving me problems. My com port and baud rate are correct and have connected rx to tx, tx to rx and gnd to gnd but get no output on my terminal screen. I have used project designer, disable the standard UART and added a "myUart" on UART port 3. I have set the output to myUart and the only line of code I have written is rprintf("hello world\n") in the main program loop (appControl) with a delay of 1 second. Terminal screen connects to com port but is blank.

Any ideas?

Thanks
Paolo

[Admin]

To be sure, how did you verify it was the correct COM port? (I just want to cover the obvious stuff first)

[Pianigro]

Hi,

I am using the Pololu Programmer on windows, it gives me two com ports, one I use to programe the chip (in my case com3), the other (in my case Com4) I connected to UART port 3 (RX to TX, TX to RX and GND to GND). I use X-CTU in windows as it has a terminal tab. Also I know X-CTU works as I use it when debugging and working with ZigBee radios (Xbee).

Regards

Paolo

[Pianigro]

BTW Happy New Year!

[Admin]

Any luck?

[Pianigro]

Hi,

Apologies for not getting back earlier, work! STill cannot access any UART. Is it possible to blow the UART functionality i.e. is it a separate thing from the ATMEGA processor?

Thanks

Paolo

[Admin]

STill cannot access any UART. Is it possible to blow the UART functionality i.e. is it a separate thing from the ATMEGA processor?

Yeap, it's definitely possible to fry individual I/O but the rest of the chip still works. I've fried about 10 digital I/O in my day, yet all other I/O on the chips still worked perfectly. I've never fried a UART before, though . . .

You've probably done this already, so apologies if you have, but I just have to ask to make sure . . . when you tried the UARTs using the Pololu device, did you double check that the baud rates are matched?


Even if you fried all hardware UARTs, you can use WebbotLib to create a software UART. It's much slower (~4kbps) and much more processor intensive, but still gets the job done. You should do this anyway to verify your Pololu device setup is operating correctly.

[Pianigro]

I have the correct com ports, baud rates etc, but I will try a software UART and play some more. I will let you know the outcome.

Thanks for all the help and feed back.

Paolo

[Pianigro]

Hi,

Software UART works so I have a solution.

FYI I thought I would try the Axon II with Arduino, I got my bot working, except for a few ports, but had the same problem, all the serial hw ports did not work (serial, serial1, serial2 & serial3). I used their NewSoftSerial or SoftwareSerial library and did get a software serial port working (used the same ports I used with AVR Studio), however Arduino did have the severe shakes as their software serial solution uses the same timer as their servo library!

Thanks for all the support
Paolo

[Admin]

It's odd that the hardware UARTs don't work for both the Axon and Arduino, but software UARTs work for both . . .

What baud rate have you tried? (in case you haven't already tried them all)


and just in case you don't already have this:
Data bits: 8, Parity: None, Stop bits: 1, Flow control: None