Robostix troubleshooting
From GumstixDocsWiki
This page will contain some troubleshooting steps that can be used to help figure out why your robostix might not be working.
Check the voltage regulators
There are a total of four voltage regulators on the robostix. All of them need to be functioning properly in order for things to work. In the picture below, the voltage regulator are identified with a blue dot and the corresponding label in blue.
The spots labelled in red are convenient places to test the voltages using a multimeter. The entire row of pins along the edge of the board at the top of the photo are ground pins, so this these are convenient places to put the black probe on your multimeter.
If you power up the robostix with nothing else attached, all 4 voltage regulators should come on, and the green power LED, located just below the power jack (right in the very bottom left corner) should be lit up.
You should measure the following nominal voltages (there will be variations for a number of reasons, perhaps by 10-15%):
| Regulator | Voltage | Description |
|---|---|---|
| VCC5 | +5 | Digital power for the ATMega128 |
| AVCC | +5 | Analog power for the ATMega128 |
| V_BATT | +5 | Goes to the hiros connector to power the gumstix |
| VCC | +3.3 | Used to power the 3.3v side of the voltage converters |
To measure VCC, use the left side of the capacitor indicated, or the pin in the top left corner of the VCC regulator.
Check the input voltage
So, if it turns out that your voltages are out of whack, then you should check the input voltage on each of the regulators. All of the voltage regulators are fed by a signal called V_ROBOBATT. This is the same voltage that lights up the green power LED that sits beside the power-jack. If the LED is on then V_ROBOBATT is present. V_ROBOBATT is the voltage that is used to power the robostix. Ideally it should be between 5v and 6v.
Now check each of the input lines on the voltage regulators. On the 8 pin voltage regulators (VCC5, AVCC, and V_BATT) there will be a small dot in one corner of the chip. This is pin 1. Pin 2, which is immediatly adjacent to pin 1, is the input voltage. Each voltage regulator has an input and output capacitor. These are convenient places to check the input and output voltages. The red dots indicate the output capacitor, and the green dots indicate the input capacitor. Note that the red/green dots are on one side of the capacitor, and this is the side that should be measured. The opposite side is ground.
It's also worthwhile checking right on the voltage regulator, being careful to only touch the pin you're trying to measure. For the VCC voltage regulator, the input voltage can be found on pin 1 (bottom left corner in the photo above).
Check the voltage regulator enables
Each of the voltage regulators also has an enable line. For V_BATT and VCC, these enable lines are connected to the input voltage. For V_BATT, the enable line is pin 1, and for the VCC voltage regulator, the enable line is pin 3 (bottom right corner in the photo above)
The VCC5 and AVCC enable lines are connected to GPIO 70 from the gumstix. There is a pullup resistor which pulls the enable line up to VCC. This pullup resisor pack is U$62, located in the bottom right corner of the photo above, just to the left of the hirose connector (just above the V_BATT written in red). These enable lines are pin 2 on the respective regulators, and should measure around 3.3v.
The pin in the top left corner should be VCC (3.3v), and the pin immediately to the right of it is GPIO70. You should measure around 3.3v on this pin.
