This directory holds code which you can build and run on a Beaglebone Black. It interfaces to an ADC-001 A/D cape, which is a 2-channel A/D board designed for data acquisition in the audio range (50Hz -- 15kHz). Complete documentation for the ADC-001 cape is available under:

https://github.com/brorson/ADC-001_hardware_information

The ADC-001 cape will be available for purchase in the near future.

The code in this directory includes a driver for the ADC-001 cape and a main program demonstrating how to take data using the ADC-001. The A/D on the cape communicates with the main processor via a SPI-like protocol. The A/D itself is an Analog Devices AD7172. The bit-banging code to talk to the A/D is implemented in C on the PRU. The PRUSS subsystem is used for communication between the ARM and the PRU. The files in this directory show how to write C code for the PRU. There is also a Makefile in this directory which builds the whole project. The project is meant to be built on the Beaglebone itself. I have not tested cross-compiling this code (yet).

Finally, I provide a device tree overlay for the ADC-001, SDB-PRU-ADC.dts. This must be loaded on your Beaglebone in the usual way to use the cape.

Stuart Brorson 4.29.2017 sdb@cloud9.net

Instructions to student: Examine main.c to see how to interact with the A/D cape. Then clone main.c and put your own code in it for your project.

Important note: This stuff works on Debian 3.8.13-bone79. No guarantees it will work on earlier or later Debian versions. Therefore, I strongly recommend you flash your BBB with Debian 3.8.13 to use these programs.

The stuff in this directory is to build both ARM and PRU executables on the BBB itself. The PRU code is written in C and built using the clpru compiler. This stuff is stand-alone -- no CCS is needed.

The ARM to PRU communication works as follows:

main sends the following to the PRU in a vector: flag saying new command has arrived number of bytes vector of bytes.

The PRU sits in a loop, doing nothing. When new data arrives, it bit-bangs clock and data lines to pump the data out two of the GPIOs.

To build the code, type "make clean && make".

To run the program, run ./main. Then follow instructions (hit return to step through various tests).

This is version of 4.10.2017. The following features/functionality are implemented:

• Communication with ADC
• ADC initialization via writing config regs on 7172.
• Read ADC ID reg. Get correct result.
• Ability to do read of single reading in single reading mode. This read takes place from user space, so the timing can be jittery. Call the fcn adc_read_single_01(); it will return the measurement as a float.
• Ability to do read of buffer of values with timing determined by the AD7172 itself. This gives non-jittered sample times. Call the fcn adc_read_multiple_01() and pass in a pointer to the buffer (of floats) to fill.
• Ability to change the sample rate. The sample rate settings are determined by the AD7172, and are documented in the AD7172 data sheet.

The PRU1 is also programmed, but communication with it is disabled. You can shut off the PRU1 by commenting out the stuff which sets the bit low in pru1.c (current active). Also, the bit in GPIOCON is set so the AD7172 will ignore the signals on the SYNC_N pin. (If the AD7172 pays attention, it will never communicate with the PRU0.)