Framework laptops are capable of being debugged and programmed from a variety of interfaces. This document describes all of them and offers some tips on what hardware is needed.

Here's a short list:

• EC & CPU UART (aka serial port), both open and closed case
• EC JTAG
• PD SWD
• SOC SPI Flash (BIOS)

EC & CPU UARTs can be accessed without opening the DUT (Device Under Test, aka the framework laptop) up by connecting to the USB Type-C ports on the right of the device (side with the power button).

The USB Type-C port needs to be told to go to debug accessory mode (see USB Type-C Cable and Connector Specifications, section "Chapter B, Debug Accessory Mode"). Then the UART TX and RX can be connected to the SBU lines (TODO: which way?).

The upper port is going to have EC UART.

The lower port is going to have CPU UART.

Note: Inserting the debugger into the DUT in the flipped orientation will swap RX and TX, resulting in not much happening.

Note 2: This is similar to Chrome OS CCD, but not quite. Chromebooks use D+ & D- USB from the GSC over the SBU lines instead of simple UART signals.

Note 3: If you happen to have a Chrome OS Servo v4 there's a way it can be configured to do this kind of UART debugging (TODO: add this in), despite UART not being common on chromebooks. That feature was added to debug some Android phones.

Thank you @DHowett for the blog post that inspired this document and tool incubation.

TODO: Add Josh Cook's https://i2clabs.com.au/ec-debug-expansion-card/

One needs a USB Type-C Male breakout board and some kind of UART interface (FTDI or any other 3.3V UART breakout / cable will probably work fine).

Note: A female breakout board does not work as Type-C cables do not pass both CC signals.

Note 1: The 1k resistor is for safety and power sequencing (eg: not killing either the DUT or the interface board if it's off while the other is on, or if the RX/TX is flipped). Feel free to substitute with something else (or 0 ohm) in a pinch.

Note 2: The table above describes the Rp/Rp (both pullup to VBUS) configuration. Rd/Rd to GND should also work.

For this you'll need to connect to various connectors on the board. You will have to open the DUT (and cope with the blinking red LEDs due to chassis intrusion). Most likely the connectors themselves will not be populated on production boards so you will have to solder them yourself. See each connector for part numbers.

This connector provides a way to program/debug the EC, see the EC booting, then see the CPU boot logs.

While the EC is very chatty and even offers a console, the CPU will probably not say anything unless the software (firmware and/or OS) is told to use the serial port.

TODO: Describe connector location.

10 pin connector, 0.5mm pitch, flat flex cable:

• Connector, DigiKey (WM1389CT-ND)
• Flex Cable, DigiKey (WM21810-ND).

TODO: figure out if we have this publicly documented somewhere else on github.

Pinout:

1. 3VL_EC
2. UART_0_CRXD_DTXD
3. EC_JTAG_TMS
4. EC_JTAG_TCK
5. EC_JTAG_TDO
6. EC_UART0_TX
7. EC_UART0_RX
8. UART_0_CTXD_DRXD
9. EC_RST#
10. GND

TODO: Figure out & Document voltage references across all boards.

This connector can be used to reflash the BIOS chip. This is useful for SOC BIOS/Firmware developers (eg: coreboot) and perhaps even unbricking from a failed BIOS upgrade.

Note: While one can reflash the BIOS with this connector the CPU might not always boot any BIOS (eg: self signed coreboot).

TODO: Describe connector location.

6 pin connector, 0.5mm pitch, flat flex cable:

• Connector, Digikey (WM1387CT-ND)
• Flex Cable, Digikey (WM25052-ND) (ignore the 10 pin picture on molex's website, it's 6 pin)

Pinout:

1. GND
2. SOC_SPI_0_CLK
3. SOC_SPI_0_D1
4. SOC_SPI_0_D0
5. SOC_SPI_0_CS#0
6. 3V_SPI

TODO: Figure out & Document voltage references across all boards.

TODO: Figure out how to avoid leaks when flashing

This connector can be used to flash and debug the PD chips. Unless you're really into USB Type-C and have the Cypress SDK ready you probably don't care about this.

TODO: Describe connector location.

6 pin connector, 0.5mm pitch, flat flex cable:

• Flex Cable, Digikey (WM25052-ND) (ignore the 10 pin picture on molex's website, it's 6 pin)
• Connector, Digikey (WM1387CT-ND)

Pinout:

1. VCC
2. GND
3. XRES
4. SWD_CLK
5. SWD_IO

A tool to interface to all of the above interfaces was developed. It can either be used in a open case or closed case configuration. It's in an expansion card form factor, so it can be docked inside a DUT.

TODO: Link or perhaps delete section for now.