Can't enter programming mode on a baby-o

Ben,

this is correct I explicitly enabled DWEN fuse. :unamused: Iā€™m currently trying to build a controller responsible for collecting wheel encoders output and providing it to main controller on-demand over i2c. This essentially requires turning baby-o into I2C slave and I need a way to debug it. Serial output is not always enough so I figured Iā€™ll risk my baby-o in exchange for greater knowledge (finding out if I can use DebugWire with baby-o ).
The issue that Iā€™m having is that Iā€™m relatively new to micros programming so I stumble a lot ( as you just observed :slight_smile:) Thanks for you support on my bouncy trip to gaining insight into the world of AVR debugging. I really appreciated it. Now, on the note of debugging which one of the rectangles left of LB1836 ( counting from the bottom/AVR ) is a CAP that I need to de-solder?

You will want to remove the fourth ā€œrectangleā€ from the bottom (starting from the bottom you should see, in order, a resistor, an LED, a capacitor, and then the capacitor you want to remove). The following picture shows the reset-line trace. The white oval encircles the pads that the capacitor spans. Click the picture for an enlarged version.

Another option would be for you to cut the red (top-side) trace somewhere between the right capacitor pad and the via, but this would pretty much permanently disconnect the resetā€™s external pull-up.

Also, make sure you donā€™t have any external devices connected to the reset line (e.g. through the hole labeled PC6 or the programming header) while youā€™re trying to use debugWIRE. Such devices could introduce capacitance that will cause debugWIRE to fail.

- Ben

Ben,

I removed the CAP like you said and everything worked like a charm. I can switch between DebugWire and ISP mode with no problems at all. Excellent staff!!! :smiley: :smiley: :smiley: :smiley:

Great thanx!!!

Also, what are the repercussions of removing the CAP on PC6?

PS: Just a thought, may be pololu could make PC6 CAP configurable through a jumper or something for the future iterations of the board.

Thatā€™s fantastic! Iā€™m very glad to hear you have everything working.

The capacitor on PC6 creates a simple low-pass filter so that a short, sudden noise spike on the reset line wonā€™t reset the Baby Orangutan. To reset the Orangutan, you need to hold the reset line low long enough for the capacitor to discharge. debugWIRE toggles the reset line so fast that the capacitor (when present) filters out the signal and causes it to fail.

Your Baby Orangutan should function just fine without the capacitor so long as you donā€™t have a noisy signal connected to PC6. If you do have a noisy signal connected to PC6, perhaps you could insert the capacitor on the signalā€™s end so that it is disconnected when signal is disconnected.

Thank you for the suggestion. We will definitely take it into consideration for future revisions.

- Ben