SIK for RedBot - mainboard reset button not working

Kits
1

I recently purchased the Inventor’s Kit for RedBot. While setting up the RedBot and running through the example sketches, I found that the Reset button on the mainboard does not appear to be working properly. When pressed, there is no apparent effect - the current sketch does not rerun as expected. For example, when using the Experiment 4 example code from the Experiment Guide for RedBot, the wheels are expected to spin for 2 seconds then stop, which should then repeat when the sketch is reset. The wheels spin as expected when I first upload the sketch, but pressing the Reset button does not cause the sketch to rerun. Power-cycling the board through either the Power switch or by unplugging and reconnecting the battery pack does result in the expected sketch-reset behavior.

I’ve attempted to do some diagnostics:

  • The switch itself appears to be intact. I read an open circuit between the two sides of the switch when the button is not pressed, and I read continuity between the sides when the button is pressed.

  • The 5V side of the switch is connected to the Reset pin of the ATMega. I read continuity with a resistance below the precision of my multimeter (reads as 0 ohm).

  • The pullup resistor appears to be working. There is 10 kOhm resistance between the 5V side of the switch and the 5V test locations on the board.

  • When the board is powered on, the 5V side of the switch and the Reset pin on the ATMega both read +5V relative to the board ground.

    • However, the ground side of the switch appears to be floating, rather than connected to ground. I read no continuity between the ground side of the switch and the GND test locations of the board, and the voltage across the two sides of the switch reads a constantly-changing value of a few mV rather than the 5V I would expect. Further, if I hold the switch closed, the Rest pin of the ATMega is unchanged at +5V relative to GND and the ground side of the switch also goes to a steady +5V.

    I tried double-checking the documentation, but electronics and electronic schematics are not my area of training, so it’s entirely possible that I am misreading the documentation. Reviewing the Eagle board schematic and the mainboard schematic on the RedBot Mainboard product page, I don’t see the Reset switch in the mainboard schematic (the ATMega Reset pin is tied directly to +5V through a 10kOhm pullup resistor, no switch), and the ground side of the switch does not appear to be connected to ground in the Eagle schematic.

    Have I missed something obvious which explains the behavior I’m (not) seeing?

    2

    The reset button is S4 in the schematic. It sounds like there’s a bad connection to ground on the switch. Try jumpering a connection between ground and pin 1 or 2 of the switch.

    /mike

    3

    Hi 0meganaught.

    Sorry for the delay in getting back too you, we’re still digging out from the holidays.

    It sounds like there may be a fault somewhere in the PCB for your RedBot. If you purchased it directly from SparkFun, just [click this link and fill in your order number and the URL to this forum post and we can arrange for a replacement.

    If you bought the board from a distributor of ours or Amazon, just contact them and they should be happy to help you out. :-)](Return Policy - SparkFun Electronics)