Getting Started: Pin Debugging

The pin test page can be used for debugging purposes for the BeagleBone's ADC, GPIO and PWM inputs. The pin test page is accessed through the navigation menu or through the following direct link: [www.experimentwebsite.uwa.edu.au/pintest] (www.experimentwebsite.uwa.edu.au/pintest.html).

The pin test page features four main areas. First is the Dashboard, where a GPIO pin or a PWM pin can be selected via a drop-down menu. Pressing "Go" after a pin is selected will activate that pin for use. Below this, an error log is shown, which will update with any errors or debugging messages that are produced by the system; keep an eye on this to see if anything is going wrong.

Below this is the ADC widget, for the analog-to-digital converters on the BeagleBone. There are eight analog inputs. To test an input, it must first be exported by checking the "export" tickbox. To export/unexport a pin essentially means to enable/disable it. You will not be able to use a pin without exporting it first. After exporting, you can set an analog value in the appropriate box for each pin. The ADCs are 12-bit and have a range of 0-4096.

Next are the GPIO controls, which will appear when a GPIO pin is selected in the drop-down menu. They work similarly to the ADC controls above, except that each GPIO pin can only be set to 0 or 1. Remember that a pin must be exported before use.

Note: For a pin diagram of the BeagleBone, see the "Pin out diagram" widget on the left of the page. The pin out diagram is also available through [this link] (www.experimentwebsite.uwa.edu.au/pinout-table.pdf).

Last are the PWM controls, which will appear when a PWM pin is selected in the drop-down menu. They work similarly to the ADC controls above, with some additional functions: frequency, duty cycle and polarity. Remember that a pin must be exported before use.

• Frequency of the generated PWM signal must be a decimal number greater than 0 (measured in Hertz).
• Duty cycle describes to proportion of time that the pin is on/off per period. The number is specified as a ratio, with values ranging from 1 (always on) to 0 (always off) by default.
• Polarity determines whether the duty cycle represents the 'active high' or 'active low' portion. By default, it represents the 'active high' portion.