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collecting-data.md

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Collecting initialization data

There is a TAS5825M driver in the System76 fork of coreboot, but each board must add the code to initialize the device.

Items required:

  • Saleae logic analyzer
  • Saleae Logic 2
  • Micro SMD grabber test clips

Be sure to unplug the battery before starting.

Attaching test clips

It may not be feasible to probe the TAS5825M chip itself. Instead look for the MOSFET that connects to the I2C clock and data lines, which will also be shown on the Smart AMP page in the schematics. Locating the MOSFET package on the board would be the next challenge.

For example:

  • oryp5: Q55, located next to the SATA connector
  • oryp6: Q54, located above the M.2 drive slot

In both these examples, pin 1 connects to the clock line and pin 4 connects to the data line. Attach a test clip to each pin, ensuring that they do not contact any other pins.

Perform a literal smoke test. With the battery unplugged, plug in the AC adapter and power on the machine. If there are any signs of being misconfigured, such as a burning smell, immediately remove power and then carefully remove the test clips.

Capturing the probe

In Saleae Logic 2, configure a capture using a rate of >4 MS/s and a timer between 5 and 10 seconds.

Start the capture and then power on the machine. When complete, power off the board and remove AC power.

In Logic 2, hide the unneeded channels and then save the capture to a file. Attempt to add an I2C analyzer with "Stream to terminal" enabled. Logic 2 may get stuck trying to analyze. If it does, close Logic 2 and reopen it.

Parsing the data

Copy the output from the Logic 2 terminal to a new file named <board>.txt in the repo. Parse the output into the format expected by the other scripts.

./parse.sh data/<board>.txt

Use the amp-c.sh and amp-rs.sh scripts to generate the C and Rust files.

./amp-c.sh data/<board>.txt > data/<board>.c
./amp-rs.sh data/<board>.txt > data/<board>.rs

Adding to coreboot

Copy the generated C file to the board directory in coreboot as tas5825m.c. Modify Makefile.inc to add the new file to ramstage. Finally, select DRIVERS_I2C_TAS5825M in the board config.

The board should now build with the smart amp driver. Flash the new firmware and test the speakers.