BeagleBoard/GSoC/2021 Proposal/bela on bbai

=Proposal-Bela support for BBAI = About Student: Dhruva Gole Mentors: Giulio Moro Code: https://github.com/BelaPlatform/Bela Wiki: https://forum.beagleboard.org/t/bela-support-for-bbai-later-ti-chips/29257/7 GSoC: GSoC entry

=Status= This project proposal has been accepted as part of GSoC 2021.

=Proposal= Bela is a hardware and software system for creating beautiful interaction with sensors and sound. This project proposes to provide restructuring and improvement of existing Bela Software Code to allow for compatibility and easier transition to newer TI chips (like in the BBAI).

About you
IRC: dhruvag2000 Github: https://github.com/DhruvaG2000 School: Veermata Jijabai Technological Inst. Country: India Primary language : English, Marathi, Hindi Typical work hours: 10AM - 7PM Indian Standard Time Previous GSoC participation: I find embedded and IOT pretty interesting, given I have experience with ESP32, SIMCOM, ESP8266, Atmega, and many other microcontroller devices and I think I will be able to excel in this project. This is the first time i am participating in GSoC.

About your project
Project name: Bela support for the BeagleBone AI My Blog: My blog related to this project and my findings. Logs : I maintain weekly progress updates here.

Description
As given on the official website, Bela is a hardware and software system for creating beautiful interaction with sensors and sound. Bela consists of a Bela cape on top of a BeagleBone Black computer (uptil now). Bela has a lot of analog and digital inputs and outputs for hooking up sensors and controlling other devices, and most importantly Bela has stereo audio i/o allowing you to interact with the world of sound. Both Bela systems use the same Bela software. It uses a customised Debian distribution which - most notably - uses a Xenomai kernel instead of a stock kernel. Xenomai is co-kernel for Linux which allows to achieve hard real-time performance on Linux machines (http://xenomai.org/). It thus takes advantage of features of the BeagleBone computers and can achieve extremely fast audio and sensor processing times. Although the proposal Title mentions support for AI, I will try to develop a standardized setup that allows an easy jump across all TI chips.
 * What is Bela?

Bela is ideal for creating anything interactive that uses sensors and sound. So far, Bela has been used to create: and many more applications that are listed here
 * Applications of Bela:
 * 1) musical instruments and audio effects
 * 2) kinetic sculptures
 * 3) wearable devices
 * 4) interactive sound installations

The Beagle Black and PocketBeagle are getting outdated by the day and also it would be better to have a more standardised setup that allows to more easily jump across TI chips, soon newer boards with different and more efficient chips like the AM5X and the TI C66x digital-signal-processor (DSP) cores in the BBAI are coming up that will need compatiblity with the Bela Software and Hardware. As part of the process we will try to offload peripheral initialisation to the mcasp and spi driver to in order to make it more portable for porting to other boards in the family, at present or future. C, PRU, dtb, uboot, make
 * Why add support for BBAI/newer TI chips?
 * Programming languages and tools to be used:

Proposed method of Implementation
Current status: The Bela cape is normally used in combination with the TI AM3358 chip on the BeagleBone Black. The hardware is currently working on the BBAI only using ALSA and the SPI driver, so the pinout and pin settings are OK, but the Bela real-time code on ARM and PRU is not running on BBAI yet. During this project I will:


 * 1) create a device tree overlay for the BELA Cape to work on the BBAI using the Cape Compatibility layer
 * 2) update the Bela code to use the McASP, GPIO and McSPI on the AM5729 SoC of the BBAI
 * 3) adapt the Bela PRU and ARM code and workflow to use the PRU via remoteproc instead of uio_pruss
 * 4) install a Xenomai patched kernel &#10003; and run the full Bela stack.

The project will involve dealing with pinmuxing, uboot, PRU assembly, C++ for Linux user space applications, the Technical Reference Manual for the Sitara family of SoCs. (ref. here)


 * Syntax Analysis

The places within the Bela core code that will require intervention are:


 * 1) in the Makefile, update the workflow to build the PRU code for remoteproc
 * 2) in core/PRU.cpp, use remoteproc instead of the libprussdrv API
 * 3) in pru/pru_rtaudio.p, the hardcoded McASP constants should be replaced with board-dependent ones.

All these changes will be made so that the same code base can run on all supported boards (e.g.: BBAI, BBB) with build- or runtime- checks. To explain in short how I aim to establish a common code base for supporting all boards, I will start off by enumerating different boards once we detect which board it is. Then in the libraries, the constants (like pin numbers and their symlinks) will be set accordingly and the rest of the code base will become much easier to use without the need to hard code anything.


 * PRU:
 * 1) The current Bela core code uses pasm to build the PRU assembly pru/pru_rtaudio.p and uses libprussdrv, which binds to the uio_pruss kernel driver to load the firmware to the PRU and handle access to the PRU RAM. Both pasm and libprussdrv are now deprecated, replaced by the clpru toolchain and remoteproc driver respectively.
 * 2) The PRU firmware contains hardcoded values for the address of the McASP, McSPI and GPIO peripherals. These addresses will change for the BBAI, so these constants need to become conditional. &#10003;(yet to be tested, but base address for the McASP of the bbai has been updated)
 * 3) As the Bela PRU firmware is written in assembly for pasm, instead of rewriting or updating it in such a way that it will stop working on the current Bela images, we will use the workflow detailed below.

The workflow below works as a proof of concept, but needs further testing. prudis file.bin | sed 's/^\(.*\)$/" \1\\n"/' > included_assembly.h 4. have the following in main.c: void main {     __asm__ __volatile__ ; } 5. build main.c with the regular clpru toolchain
 * Workflow for building the existing pasm PRU code with clpru:
 * 1) Build the .p file as is with pasm with -V2 -b. This generates a .bin file that contains the assembled program
 * 2) I will be using the disassembler Giulio Moro put together hacking the one that was inside prudebug. (Find it here(built with gcc da.c -o prudis) . (Note: A disassembler is a computer program that translates machine language into assembly language)
 * 3) Process the bin through the disassembelr and make it ready to be included inside an __asm__ directive (i.e.: add quotes and prepend a space at the beginning of each line):
 * 1) include "included_assembly.h"

6. I will also need to change these MCASP addresses in pru/pru_rtaudio.p :


 * 1) define MCASP0_BASE 0x48038000
 * 2) define MCASP1_BASE 0x4803C000


 * 1) define MCASP0_DATAPORT 0x46000000
 * 2) define MCASP1_DATAPORT 0x46400000

Additionally, I will need to compare the McASP and McSPI sections of the AM5729 and AM3358 manuals to verify that all the registers of the McASP and McSPI peripherals kept the same meaning and offsets between the two chips, or adjust the code accordingly.

I am yet to figure out pinmuxing to make sure the relevant pins are set to the correct function (they are NOT by default). I will see here https://elinux.org/BeagleBoard/GSoC/2020_Projects/Cape_Compatibility and/or ask on the BB slack about for the best way to go about it. I have so far created a basic AUDIO overlay (named BBAI-AUDI-02-00A0.dts) that has been merged into the beagleboard / BeagleBoard-DeviceTrees repository.
 * PINMUXING

Bela can work with a PRU->ARM interrupt, which is default these days, but requires an rtdm driver, which is another layer of complications. As an intermediate step to avoid further complications, I will try to run it without the PRU->ARM interrupt by adding BELA_USE_DEFINE=BELA_USE_POLL to my make command line. After building the Xenomai kernel, I will build the rtdm_ kernel and revert to using PRU->ARM interrupts.
 * PRU->ARM INTERRUPTS

The Remote Processor Framework (rproc) allows different platforms/architectures to control (power on, load firmware, power off) those remote processors while abstracting the hardware differences, so the entire driver doesn't need to be duplicated. I will need to change the initialization code in PRU.cpp that is currently relying on lib prussdrv and move to rproc. Not sure if rproc provides some functionalities to access the PRU's RAM the way prussdrv_map_prumem used to, but that essentially gives access to a previously mmap'ed area of memory, so it should be easy to replace, as long as I am able to find the correct addresses in the TRM. On the latest Bela code there's a Mmap class which can make this somehow simpler [http://docs.bela.io/classMmap.html ref. here].
 * PRU transitioning from libprussdrv to rproc

Xenomai kernel (v4.19.94-ti-xenomai-r64) has been built and tested for the BBAI. I have installed the xenomai kernel and libraries through the default procedure to update kernel. I have also managed to successfully build the entire Bela core code on the BBAI so far.
 * XENOMAI kernel

The hardware listed below will be necessary for testing if my code implementation works correctly on the hardware.
 * Hardware required:
 * 1) BeagleBone AI.
 * 2) Bela cape: The original Bela board.

Experience and approach

 * 1) I have used C++, C and Python programming languages over the past 3 years in a variety of projects involving embedded systems using the ESP32, Arduino UNO, ESP8266 and am also well-versed with freeRTOS.
 * 2) I have an aptitude for writing good reports and blogs, and have written a small blog on how to use a debugger.
 * 3) I recently did a project using ESP32, in which I used the DHT11 sensor to display humidity and temperature on a local HTML server . Other than that I have worked on developing hardware and making documentation for a 3 DOF arm based on an ESP32 custom board.
 * 4) I also interned at an embedded device startup where I
 * 5) Interfaced ADS1115 ADC with the ESP32 and used it to read battery voltage.
 * 6) Used UART for ESP32 and SIMCOM SIM 7600IE communication to gain LTE support.
 * 7) Published local sensor data to the cloud via LTE.
 * 8) I actively contribute to open source (most recently, I contributed to the ADS1115 library for ESP32 on the unclerus repo and can be seen here).
 * 9) Currently I am working on designing a Development board for the Raspberry Pico (RP2040) using KiCAD.
 * 10) I also do a lot of mini projects throughout the year, you can find my several more interesting projects at my github page

Contingency
I believe that if I get stuck on my project and my mentor isn’t around, I will use the resources that are available to me. Some of those information portals are listed below.


 * 1) Derek Molloy's beagle bone guide provides all the information needed for getting up and running with my beagle.
 * 2) remoteproc
 * 3) BBAI vs BBB pin headers Google Sheet
 * 4) beaglebone pru gpio example
 * 5) official BELA website
 * 6) Ask on the BeagleBoard.org forum

Benefit
If successfully completed, this project will add support for the Bela cape + Xenomai + PRU on the BeagleBone AI, and also the code will be easier to port to other Texas Instruments systems-on-chip.

'' By going through the steps needed to have the Bela environment running on BBAI, we will go through refactoring and rationalisation, using mainline drivers and APIs where possible. This will make Bela easier to maintain and to port to new platforms, benefiting the project's longevity and allowing it to expand its user base.'' -Giulio Moro

Misc
Completed all the requirements listed on the ideas page. The code for the cross-compilation task can be found here submitted through pull request #149.