This is a software library that allows access to the General Purpose Inputs and Outputs and the Digital Analog Converters in the BeagleBone Black single board computer.
- Can be used as a library for programs written in the C language or as an external for PureData patches.
- Analog Digital Converters and General Purpose IO pins can be configured without the need of writing or configuring Device Tree Overlays.
- To avoid high CPU usage, input polling is done using one of the Programmable Real Time Units PRUs available in the AM335X chip (the Beagle Bone Black's main processor).
- Easy to use. Users don't have to learn how to access the hardware features, no need to compile PRU code, etc.
- ADC inputs are sampled at 1500 samples per second. Useful for sensors, potentiometers, etc. Not so much for audio signals.
You'll need to figure out yourself how to get internet access on your Beaglebone, how to run PD patches and/or how to compile C programs. All of the following was tested on Debian Linux running on a BeagleBone Black revision C.
Here's an example patch that uses the library to get input from a potentiometer and a pushbutton and drives an LED. See the test-patches directory and the help files in puredata-external for more info.
You're probably using a headless BeagleBone (no screen, keyboard or mouse) so you'll need to create your PD patches on a different computer and then copy them to your BeagleBone. I have included a 64 bit Linux version of the PD library in the puredata-external directory. You'll need to rename the beaglebone.pd_linux_x86_64 file to beaglebone.pd_linux and put it somewhere in your PD path if you want to use it while creating patches in your computer. Binaries for other platforms are welcome.
Here's a possible way of using the library from a C program. For a full example and it's makefile, check the c-example directory, for the full API, see beaglebone_pruio.h.
#include <beaglebone_pruio.h>
#include <beaglebone_pruio_pins.h>
int main(int argc, const char *argv[]){
// Initialize library and hardware.
beaglebone_pruio_start();
// Get input from ADC channel 2.
int beaglebone_pruio_init_adc_pin(2);
// Use pin P9_11 as an input.
int beaglebone_pruio_init_gpio_pin("P9_11", BEAGLEBONE_PRUIO_INPUT_MODE);
// Use pin P9_12 as an output.
int beaglebone_pruio_init_gpio_pin("P9_12", BEAGLEBONE_PRUIO_OUTPUT_MODE);
int output_value = 0;
while(!exit_condition){
// Get available messages from digital and analog inputs and parse them:
beaglebone_pruio_message message;
while(beaglebone_pruio_messages_are_available()){
beaglebone_pruio_read_message(&message);
// Message from gpio
if(message.is_gpio && message.gpio_number==P9_11){
printf("P9_11: %i\n", message.value);
}
// Messages from adc
else if(!message.is_gpio && message.adc_channel==2){
printf("ADC_2: %i\n", message.value);
}
}
// Toggle output pin
output_value = !output_value;
beaglebone_pruio_set_pin_value(P9_12, output_value);
sleep(1);
}
beaglebone_pruio_stop();
}Make sure your BeagleBone has internet access, download the library and run the install.sh script. Read the script before running it! You might not want to run some of the commands in there.
git clone https://github.com/outer-space-sounds/beaglebone-pruio.git beaglebone-pruio
cd beaglebone-pruio/scripts
./install.shThe library assumes there is an analog multiplexer connected at the input of ADC6. This allows for using 14 ADC channels instead of just 7. 3 GPIO pins are used to control the mux: P9_27, P9_30 and P9_42A. An option to turn this off can be added if there is interest. Here's a schematic. Pins labeled "BBB" are pins in the BeagleBone Black, pins labeled with "ADC" are the analog inputs you can use.
Use the issue tracker in this github repository.
This is only needed if you want to somehow change the library (fix a bug, contribute a new feature, whatever).
There are two main components of the library: the ARM part that runs on the main processor in the BeagleBone and the PRU part that runs on one of the PRU units. Communication between both processors is done through a ring buffer in shared memory space.
Compilation is done on the BeagleBone itself (I never bothered to set up a cross-compilation thing) so you'll need to install two compilers on your board. First one, for the ARM part is gcc, which can be installed by doing apt-get install build-essential. The second one, for the PRU part, is Texas Instrument's PRU compiler, which can be downloaded here. It's free as in beer and you'll need to sign up with TI before downloading. Uncompress it and put it in the vendors/pru_2.0.0B2 directory so that our makefile finds it and uses it. Your vendors directory should end up looking like this:
vendors
│
├── am335x_pru_package
│ ├── am335xPruPackage_1_2_Manifest.pdf
│ ├── am335xPruReferenceGuide.pdf
│ ├── Documentation
│ ├── Makefile
│ ├── pru_sw
│ └── README.txt
└── pru_2.0.0B2
├── bin
├── bin.cmd
├── example
├── include
├── lib
├── License.txt
├── LICENSE.txt
├── man
├── PRU_Compiler_2_0_manifest.html
└── README.txt
After having both compilers, library/Makefile takes care of everything. If you're changing PRU code, also take a look at AM3359_PRU.cmd and bin.cmd.
Beaglebone Pruio.
Copyright (C) 2015 Rafael Vega [email protected]
This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.
This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
You should have received a copy of the GNU General Public License along with this program. If not, see http://www.gnu.org/licenses/.