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USB-PD Sniffer


This page describes a USB-PD sniffing dongle with Type-C connectors. The dongle can be supported by Chrome devices as part of a USB-Type C implementation.

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Hardware Capabilities


Complete schematics, layout, and enclosure are attached at the bottom of this page.

Firmware Source Code

The firmware is located In the Chromium Embedded Controller repository under board/twinkie/, the release version is on the firmware-twinkie-9628.B branch :

Building Firmware

Within your Chromium OS chroot, the syntax is:

For the impatient, here is a very cut-down version of the detailed instructions. 
If anything here gives you trouble, refer to the [official documentation]( instead.


## Install the prerequisite tools

goobuntu$  	sudo apt-get install git-core gitk git-gui subversion curl
goobuntu$  	git clone <>
goobuntu$  	export PATH=$(pwd)/depot_tools:$PATH

none&#10;&#10;## Check out the sources&#10;&#10;

goobuntu$  	mkdir chromiumos && cd chromiumos
goobuntu$  	repo init -u \
                    --repo-url \
                    -g minilayout -b firmware-twinkie-9628.B
goobuntu$  	repo sync

none&#10;&#10;## Enter the chroot&#10;&#10;

goobuntu$  	cros_sdk

none&#10;&#10;## Install the board-specific compiler toolchain&#10;&#10;

chroot$  	./setup_board --board=falco

none&#10;&#10;## Check out the EC sources&#10;&#10;

chroot$  cros_workon-falco start chromeos-ec
chroot$  repo sync ../platform/ec

none&#10;&#10;## Build things&#10;&#10;

chroot$	 cd ../platform/ec
chroot$  make BOARD=twinkie -j

Alternately, you can use the pre-built firmware twinkie_v1.11.19-9e81762f2.bin attached at the bottom of this page.

Flashing Firmware

The USB-PD dongle behaves as a USB DFU device when the ID pin is grounded on the USB micro-B connector.

This is done either by plugging an A-A USB cable into an A-to-microB OTG adapter as shown in the photo below

or by typing the dfu command on the USB console (if you already have a recent firmware, e.g. v1.11.19+).

Within your Chromium OS chroot:

./util/flash_ec --board=twinkie

or on Ubuntu Linux:

sudo apt-get install dfu-util
sudo dfu-util -a 0 -s 0x08000000 -D twinkie_v1.11.19-9e81762f2.bin

Programming Twinkie with OTG and A-to-A cables

if you have entered the DFU mode by using the dfu console command, you need to use the following command to exit it :

sudo dfu-util -a 0 -s 0x08000000:force:unprotect -D twinkie_v1.11.19-9e81762f2.bin

else plugging the regular USB cable will do it automatically.

Using the Integrated Command Line over USB

The USB-PD dongle exports its internal command-line console as a pair of USB bulk endpoints.

On a Linux system, you get the console as a /dev/ttyUSBn device.

On recent systems (kernel v3.19+), this ttyUSB device should be instantiated automatically, or other systems you can try using the usbserial kernel module :

echo '18d1 500A' | sudo tee /sys/bus/usb-serial/drivers/generic/new_id

If this fails, you might need to run sudo modprobe usbserial first.

Using as a PD Packet Sniffer

You can use the opensource Sigrok framework to acquire and decode USB Power Delivery traces with the USB-PD dongle. You can then use Pulseview to display them.

The patches for the Sigrok hardware driver for the dongle is not in the upstream packages yet.

The packages below also include the bleeding edge version of Pulseview which has a convenient "Tabular Decoder Output View".

If your machine has an x86_64 processor, you can try the following experimental pre-built packages:

cd $(mktemp -d)
wget \ \ \ \
sudo dpkg -i *.deb
sudo apt-get install -f
cd $(mktemp -d)
wget \ \ \ \
sudo dpkg -i *.deb
sudo apt-get install -f
cd $(mktemp -d)
wget \ \ \ \
sudo dpkg -i *.deb
sudo apt-get install -f
cd $(mktemp -d)
wget \ \ \ \
sudo dpkg -i *.deb
sudo apt-get install -f

If you want to do a full build from sources of sigrok and pulseview with Twinkie support,

now the USB PD protocol decoder is now upstreamed in libsigrokdecode (and sigrok-cli / pulseview are working out-of-the-box).

You only need to add the Chromium Twinkie hardware driver in libsigrok : last version of the patch applying on libsigrok-0.5.2 plus the VBUS support

A recipe to do this build is written down in Build Sigrok and Pulseview from sources.

Capturing traces with the Sigrok tool

sigrok-cli -d chromium-twinkie --continuous -o

Real-time decoding of USB PD packets while capturing

sigrok-cli -d chromium-twinkie --continuous -P usb_power_delivery:cc=CC1:fulltext=yes -P usb_power_delivery:cc=CC2:fulltext=yes -A usb_power_delivery=text

Displaying and decoding PD traces

pulseview & 

Add the USB PD decoder from the Decoders menu, then edit the instantiated decoder to select the appropriate CC line.





Experimental VBUS analog traces

As shown on the pictures above, you can try to capture the VBUS analog voltage and current along with the CCx lines traffic.

This feature is still experimental and might have negative side effects on your PD packets capture !

Capturing VBUS voltage only and CCx traffic:

sigrok-cli  -d chromium-twinkie:analog_channels=1 --continuous -o

Capturing VBUS voltage and current and CCx traffic:

sigrok-cli  -d chromium-twinkie:analog_channels=2 --continuous -o

then you can display the .sr files in Pulseview.

Using as a Power Sink

  1. Use the tw sink command. Exit sink mode by using the reboot command.
  2. When a power source is detected, the dongle negotiates a power contract, activating the green LED for 5V, the red LED for 20V, or the blue LED for other voltage.
  3. You can change the maximum negotiated voltage with the following command in the dongle USB shell: pd 0 dev 12 This example sets a limit of 12 V.