Twonkie Introduction

Twonkie is an open source USB Power Delivery protocol sniffer and debugging tool, created by Joachim "dojoe" Fenkes, based on Google's Twinkie. It can:

• Measure voltage and current on the Vbus and Vconn rails (version 2.0 can handle EPR voltages up to 48V)
• Capture USB-PD packets for later analysis
• Pass through signals at full speed (20Gb/s lanes are verified to work)
• Send USB-PD packets

Twonkie can be bought in 3mdeb shop.

Links:

• Project page
• Original Twinkie documentation

Setup

Preparation

For flashing and using the Twonkie, you will need to install dfu-util and minicom. You can find them in your Linux distro's repositories:

Ubuntu / DebianFedoraArch

$ sudo apt install dfu-util minicom

$ sudo dnf install dfu-util minicom

$ sudo pacman -S dfu-util minicom

Flashing

Steps to flash firmware to the Twonkie:

1. Download the latest firmware from the project's release page
2. While holding the SW1 button on the Twonkie, connect it to your computer using a USB micro-B cable

3. Verify in lsusb that the device has booted in DFU mode:

   $ lsusb | grep 0483:df11
   Bus 003 Device 083: ID 0483:df11 STMicroelectronics STM Device in DFU Mode
   

4. Navigate to the location where you downloaded the firmware

5. Flash the firmware:

   $ sudo dfu-util -a 0 -s 0x08000000 -D ~/Downloads/twonkiev2-20230611.bin
   

   The command may take a long time to complete. Do not be alarmed if progress appears to stop. 1. Disconnect and reconnect the newly flashed Twonkie to reboot it into the firmware 1. Verify in lsusb that the device has booted into firmware:

   $ lsusb | grep 18d1:500a
   Bus 003 Device 084: ID 18d1:500a Google Inc. Twinkie
   

Testing

Sniffing a PD negotiation

1. Open minicom on Twonkie's console:

   $ sudo minicom -D /dev/ttyUSB0
   

2. Type in tw trace on to start logging

3. Connect a twonkie between a USB-PD power supply and a USB-PD power sink
4. Verify that the device is charging and logs appear on the screen

Example output:

> tw trace on
33.754913 SRC/0 [41a1]SRCCAP 5000mV/3000mA 9000mV/3000mA 15000mV/3000mA 20000mV/3250mA
33.906189 SRC/0 [41a1]SRCCAP 5000mV/3000mA 9000mV/3000mA 15000mV/3000mA 20000mV/3250mA
34.057128 SRC/0 [41a1]SRCCAP 5000mV/3000mA 9000mV/3000mA 15000mV/3000mA 20000mV/3250mA
34.208091 SRC/0 [41a1]SRCCAP 5000mV/3000mA 9000mV/3000mA 15000mV/3000mA 20000mV/3250mA
34.359253 SRC/0 [41a1]SRCCAP 5000mV/3000mA 9000mV/3000mA 15000mV/3000mA 20000mV/3250mA
34.360608 SNK/0 [0041]GOODCRC
34.364597 SNK/0 [1082]REQUEST{4} 43851545
34.365421 SRC/0 [0121]GOODCRC
34.367411 SRC/1 [03a3]ACCEPT
34.368118 SNK/1 [0241]GOODCRC
34.593451 SRC/2 [05a6]PSRDY
34.594166 SNK/2 [0441]GOODCRC
34.595642 SRC/3 [17af]VDM Vff00:DISCSVID,INI:ff00a002
34.597310 SRC/3 [17af]VDM Vff00:DISCSVID,INI:ff00a002
34.598213 SNK/3 [0641]GOODCRC
34.602898 SNK/1 [328f]VDM Vff00:DISCSVID,ACK:ff00a042 8087ff01 00000000
34.603946 SRC/1 [0321]GOODCRC

Measuring voltage and current

1. Open minicom on Twonkie's console:

   $ sudo minicom -D /dev/ttyUSB0
   

2. Connect a twonkie between a USB-PD power supply and a USB-PD power sink

3. Type in tw vbus to display the voltage and current measurement

Example output:

> tw vbus
VBUS = 20112 mV ; -1274 mA

Power sink

1. Open minicom on Twonkie's console:

   $ sudo minicom -D /dev/ttyUSB0
   

2. Connect a twonkie between a USB-PD power supply and a USB-PD power meter

3. Type in tw sink to enable sink mode - the firmware will reboot at this point
4. Type in pd 0 dev 20 to set voltage limit to 20V
5. Verify that the power meter turns on and displays 20V measured at the USB-C plug
6. Verify that the RGB LED has changed its color to red

Example of a successful test: