tedium

TDM telephony experimentation

Dependencies

• oss-cad-suite: open-source digital design and verification tools, with nightly binary builds.
• poetry: Python dependencies and packaging management tool.
• g++-riscv64-linux-gnu
• rustup toolchain install stable -t riscv32i-unknown-none-elf

Installation

Clone this repository, and generally follow these steps:

$ cd tedium
# Grant access through `udev` to the FTDI JTAG interface on the Tedium board.
$ sudo ln -sf ./99-tedium.rules /etc/udev/rules.d/
$ sudo udevadm control --reload-rules && sudo udevadm trigger
#
$ pip3 install poetry --user
# Might need to log out and in to get ~/.local/bin in PATH.
# Or, `source ~/.profile`.
# Set up virtual environment, download and install dependencies
$ poetry install
# Enter poetry shell
$ poetry shell
# Include OSS CAD Suite tools in PATH
$ export PATH="/home/jboone/src/fpga/oss-cad-suite/bin:$PATH"
# Build and download FPGA bitstream
# LUNA_AVOID_BLOCKRAM required for reliable USB enumeration as of 2022/May/02.
$ LUNA_AVOID_BLOCKRAM=1 applets/tedium-fpga
# After the bitstream is generated, you can inspect the results in the `build` directory.
# Initialize the framer/LIU
$ cargo run --release --bin tedium-tool -- init
# Run the host-side audio and event engine
$ cargo run --release --bin tedium-tool -- monitor

NOTE: My Tedium .venv got weird when I had the "OSS CAD Suite" environment already enabled. Poetry would download dependencies on poetry install or poetry update, but would then delete them when running poetry run or poetry shell.

Testing

Unit tests may be run like this:

$ python3 -m unittest tests.hdl.tx_usb_to_fifo
# Or the name of any other HDL test module you want to run/simulate.

USB Debugging

$ sudo cat /sys/kernel/debug/usb/devices
$ sudo cat /sys/kernel/debug/dynamic_debug/control | grep "snd_usb_audio"
$ sudo echo 'file sound/usb/* +p' >/sys/kernel/debug/dynamic_debug/control
$ sudo sysctl -w kernel.printk=7 # debug-level messages
$ sudo sysctl kernel.printk

Using Wireshark

$ sudo modprobe usbmon
$ sudo wireshark
# Capture stuff

Wireshark filters that might be of use:

# Find USB IN on endpoint 1, where the frame of completed inbound URBs is not the typical length.
# This helps find where the async audio input FIFO level is wrapping around.
usb.endpoint_address.number==1 && usb.endpoint_address.direction==IN && usb.urb_type=='C' && frame.len != 1728
# Set the time reference at an interesting record in Wireshark, disable view filtering, and work from there.
# Note that "marked" records appear regardless of whether they match the view filter, which is very handy.
# Now match on USB OUT records that have been submitted (pending transmission)
usb.endpoint_address.number==1 && usb.endpoint_address.direction==OUT && usb.urb_type=='S'

However, it seems like Wireshark isn't showing complete URB buffer contents?

Trouble With Real-Time Kit

# Is there an `rtkit` user?
$ getent passwd rtkit
# Is there an `rtkit*` user?
$ ps ax | grep -i rtkit
# Check that RTKit is actually changing our process/thread priority:
$ journalctl -e -t rtkit-daemon
# `ulimit` values:
$ ulimit -a

Use

See the software README for information on how to use tedium-tool to interact with the hardware over USB.

License

This software and gateware in this project is licensed under the BSD 3-Clause License.

The hardware is licensed under the CERN Open Hardware Licence Version 2 - Permissive.