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Powering Bela

The best ways to get power to your board

When you have finished programming your project you may want to make it fully embedded and power it with a battery or external wall plug. In this guide we discuss the best ways to power your Bela board.

Table of contents

  1. Using an external power supply
  2. Using batteries and power banks
  3. Using the speaker amplifiers on Bela
  4. Using LiPo batteries

Using an external power supply

Bela

You can power Bela from an external 5V DC power supply either with a USB cable plugging into Bela’s mini or micro USB B port or a barrel cable. If you use the mini/micro USB port then you can use a standard 5V USB plug which are commonly used for phone chargers to give power via the USB B port. If you are using a barrel cable then it needs to be 5.5mm x 2.1mm with the negative voltage outside and the positive voltage inside (often referred to as “centre positive” or “tip positive”).

On the Bela cape, connector J1 (not populated by default) can be used as an alternate means of supplying power to the speaker amplifiers. Pin 1 of J1 is connected to the same pins on the BeagleBone Black as the barrel connector (P9, pins 5 and 6).

Important

Only 5V power supplies of the correct polarity should be used with the barrel connector or J1. Connecting more than 5V to the barrel connector, or connecting the supply backwards, may destroy the BeagleBone Black and the Bela cape.

Bela Mini

In addition to power Bela Mini via the USB port you can connect an external 5V power supply between one of the GND pins and P1.01. See here for more details on powering the PocketBeagle.

Using batteries and power banks

Standard 5V power banks which are commonly used to charge mobile phones, and come in all sorts of sizes and capacities, are an easy option for powering both Bela and Bela Mini. These can be used via the USB port or the barrel jack with an appropriate USB to barrel jack cable (to power the speaker amps).

An embedded Bela project, the Air Harp by Christian Heinrichs, which is powered with a USB power bank commonly used for charging phones.

Remember that if you want your project to run automatically when the board powers up then you will need to configure it to run on boot.

Using the speaker amplifiers on Bela

The internal power amplifier which drives the speaker outputs (on the Bela cape only) is powered only when the barrel jack is in use.

J1 also provides a way to power the speaker amplifiers on the Beaglebone Green, which does not have a barrel connector. Alternatively, by desoldering ferrite bead FB4 from the Bela cape (located right next to J1), the speaker amplifiers can be powered from a separate supply to the rest of the Beaglebone.

Using LiPo batteries

If you would like to use a LiPo battery to power your project then it is a good idea to use a booster like the following to jump the LiPo power supply up to 5V: https://learn.sparkfun.com/tutorials/sparkfun-5v1a-lipo-chargerbooster-hookup-guide/all

Note

Powering Bela and Bela Mini from a battery with less than 4.5V will cause the analog inputs and outputs to stop working. The USB Host will also stop working. If you need to use these we highly recommend using a booster.

The above solution with a booster will generate 5V from a 3.7V LiPo and so all analog I/O will work. It also works with both Bela and Bela Mini. Note that on Bela Mini you should wire the Power to P1.01 and GND to any of the available grounds, and not to the dedicated battery sockets mentioned in the LiPo section below.

Bela Mini

The PocketBeagle also comes with native support for LiPo batteries. On P2 header Pin 14 (labelled BAT+ at the back of the PocketBeagle) is the positive input for a single cell lithium (lion/lipo) battery. P2 Pin 15 (labelled GND) is the battery ground.

In order to switch on Bela it is necessary to connect P2 Pin 12 (labelled PB) to GND and then to disconnect it, like a switch. This acts like the main power button on the PocketBeagle and is a good place to attach a master power switch if you are embedding your project.

The data sheet lists a supply voltage for the battery input as between 2.75V and 5.5V. We have tested some common 3.7V LiPo batteries like these and they work great.

Note

Powering Bela Mini from a battery with less than 4.5V will cause the analog inputs to stop working.

Re-charging

If you want the LiPo battery to recharge while the board is powered over USB, you additionally have to connect a 10k resistor between P2.15 and P2.16. To check the battery is charging:

  • run i2cget -y -f 0 0x24 0x03 to check the PMIC charging status via I2C
  • output should be 0b0001000
  • see PMIC datasheet for more info

You can also find an extensive discussion of using LiPo batteries with Bela Mini on our forum.

Powering off

The 4.4 Linux kernel that comes with Bela image < v0.3.8 does not fully power off the board when shutting it down and may need a physical switch to turn off the battery, or briefly disconnect it upon power down. Newer images (June 2020 onwards) with 4.14 kernel or above will work as expected.