How do I define GPIO pin 4 as an output?

Hi there,

I am playing around with my Raspi B + PiBrella board and I want to use GPIO pin 4 as an output.
From the default instal it is defined as a serial port for 1-wire sensors only.

How do I configure Webiopi and Cayenne?
Many thanks,

Hey there Martin,

Welcome! We have reserved GPIO 4 for automatic 1-wire sensors. If you connect 1-wire sensors to pin 4, then the sensor will automatically be discovered and put as a widget in your dashboard.

Webiopi is installed when Cayenne is installed. Can you clarify you question?


Hi B,

It is kinda working now…
I have disabled DeviceTree and I2C using Cayenne config. I have edited /ect/webiopi/config and made GPIO pin 4 an output. I can now switch the red LED on the Pibrella board on and off, using the Webiopi interface on
But I can’t add a Generic Output device on the Cayenne dashboard for this output. This is also true for another output on GPIO pin 27 (not in the dropdown list of choices). How do I make the Cayenne dashboard resemble the PiBrella board more?

Hi Martin,

My recommendation is not to ‘mess’ with the webiopi config. We’ve noticed that it can lead to issues with Cayenne, since Cayenne is using a modified webiopi.

GPIO 4 is reserved specifically for automatically discovering 1-wire devices, so we have not listed it as available to add a widget for GPIO 4. Pin 27 should be available in the dropdown when adding a generic output, I’ve had to zoom out before so I can see the full dropdown list (with pin 27 at the bottom), maybe try this?

Admittedly, we’ve never had anyone tell us they are using a PiBrella! So I’m glad you are bringing this up. @eptak what do you think?

Hi B,
The Pibrella is a nice little board for demonstrations, because it has a few LEDs, 4 protected inputs and 4 high power outputs for switching relais and motors. Yesterday I found GPIO pin 27 (for the green LED on Pibrella) and added a switch for it on the Cayenne dashboard. Thanks for the tip.

The Pibrella piezo buzzer on GPIO pin 18 doesn’t work on Cayenne for now, because I can’t get PWM to work on this pin. Any tips?

I’ve gotten a piezo buzzer to work, but need to use a PWM like PCA9685. The native Pi PWM isn’t compatible with WebIOPi or Cayenne. Do you have a PWM? I have extra one I can send you :wink:


Dear B,

As I said I am just playing around with my Pibrella board. But I would like the spare PWM you have lying around… :wink: I will DM you.

I guess I am Helped…

Helped! lol :slightly_smiling: