# FPMCU Development for Partners This document is intended to help partners (sensor vendors, MCU vendors, etc) that are currently (or interested in) developing fingerprint solutions for Chromebooks. The document assumes that you're using Linux to do the development; preferably a recent version of Ubuntu or Debian. Some partners have had success developing in a VM, but please note that we don't test that configuration. See the [FPMCU documentation] for additional development information. [TOC] ## Hardware Required for Standalone Development (no Chromebook) The following hardware components can be used to set up a standalone development environment for FPMCU development (i.e., it does not rely on a Chromebook). Development for other [EC]s is often done in a similar manner, but some of them have their own standalone development or evaluation kits that don't require the use of [servo]. You will need an [FPMCU reference board](#fpmcu-dev-board) and a [servo debugger](#servo). ### FPMCU board {#fpmcu-dev-board} The Fingerprint MCU (FPMCU) board has the MCU that handles all fingerprint-related functionality (matching, encryption, etc). The fingerprint sensor itself connects to the FPMCU board. *** note Older revisions of these boards are not supported. If you have an older version of the board, please request a replacement. *** This FPMCU board is the Dragonclaw Rev 0.3. | ------------------------------------------- | ![Dragonclaw board] | Download the [Dragonclaw schematics, layout, and BOM][dragonclaw schematics]. *** note **Googlers**: You can pick up a Dragonclaw development board at Chromestop. **Partners**: You can request a Dragonclaw development board from Google. *** This FPMCU board is Icetower Rev 0.1. | ------------------------------------- | ![Icetower board] | *** note **Googlers**: You can pick up an Icetower development board at Chromestop. **Partners**: You can request an Icetower development board from Google. *** ### Servo Servo is a general purpose debug board that connects to a header on the FPMCU board. Among other things, the servo supplies power to the FPMCU and can be used to program the FPMCU, interact with the EC console, take power measurements, and debug a running program. There are several variants of Servo and the fingerprint team uses the [Servo Micro](#servo-micro) for its simplicity. It lacks builtin JTAG/SWD support for single step debugging, but Dragonclaw v0.3 and Icetower v0.1 have an [SWD connector](#servo-micro-swd) that can be used. [Servo Micro](#servo-micro) | --------------------------- | ![Servo Micro] | *** note For more information about Servo, see [servo]. *** ### Servo Micro Servo Micro does not require any adapters to interface with the FPMCU board. As you can see below, one end connects to the FPMCU board and the other connect to the developer's computer over micro USB. ![Servo Micro with Dragonclaw] *** note For more information about Servo Micro, see [Servo Micro Info]. *** #### Using SWD (Optional) {#servo-micro-swd} Instructions for setup are described in [Fingerprint Debugging]. ## Software Setup ### Get the Chromium OS source code * First, make sure you [have the prerequisites]. * Then [get the source]. * Create and [enter the `chroot`]. * You can stop after the `enter the chroot` step. ### Build the [EC]\ (embedded controller) codebase Open **two** terminals and enter the chroot in each: ```bash # from a terminal on your machine (outside chroot) $ cd ~/chromiumos/src # enter the chroot (outside chroot) $ cros_sdk ``` *** note NOTE: More information on servo can be found in the [servo] documentation. *** In one of the terminals, build and start `servod` Build and install `servod` in the chroot: ```bash (chroot) $ sudo emerge hdctools ``` *** note In all of the following commands, replace `` in the command with `bloonchipper` or `dartmonkey` depending on the development board you are using. *** Run `servod`: ```bash (chroot) $ sudo servod --board= ``` You should see something like this. Leave it running: ```bash 2023-02-03 15:05:30,632 - servod - INFO - Start 2023-02-03 15:05:30,639 - servod - INFO - Found XML overlay for board icetower 2023-02-03 15:05:30,639 - SystemConfig - INFO - Loading XML config (/usr/lib64/python3.6/site-packages/servo/data/servo_micro.xml, None, 0) 2023-02-03 15:05:30,640 - SystemConfig - INFO - Loading XML config (/usr/lib64/python3.6/site-packages/servo/data/common.xml, None, 0) 2023-02-03 15:05:30,640 - SystemConfig - INFO - Loading XML config (/usr/lib64/python3.6/site-packages/servo/data/power_tools.xml, None, 0) 2023-02-03 15:05:30,642 - SystemConfig - INFO - Loading XML config (/usr/lib64/python3.6/site-packages/servo/data/keyboard.xml, None, 0) 2023-02-03 15:05:30,644 - SystemConfig - INFO - Loading XML config (/usr/lib64/python3.6/site-packages/servo/data/uart_common.xml, None, 0) 2023-02-03 15:05:30,644 - SystemConfig - INFO - Loading XML config (/usr/lib64/python3.6/site-packages/servo/data/ec_info.xml, None, 0) 2023-02-03 15:05:30,645 - SystemConfig - INFO - Loading XML config (/usr/lib64/python3.6/site-packages/servo/data/cpu_fw_spi.xml, None, 0) 2023-02-03 15:05:30,645 - SystemConfig - INFO - Loading XML config (/usr/lib64/python3.6/site-packages/servo/data/servo_adc_enabled_noop.xml, None, 0) 2023-02-03 15:05:30,648 - SystemConfig - INFO - Loading XML config (/usr/lib64/python3.6/site-packages/servo/data/servo_icetower_overlay.xml, None, 0) 2023-02-03 15:05:30,648 - SystemConfig - INFO - Loading XML config (/usr/lib64/python3.6/site-packages/servo/data/servo_fpmcu_dev_board_common_overlay.xml, None, 0) 2023-02-03 15:05:30,649 - SystemConfig - INFO - Loading XML config (/usr/lib64/python3.6/site-packages/servo/data/servoflex_v2_r0_p50.xml, None, 0) 2023-02-03 15:05:30,649 - SystemConfig - INFO - Loading XML config (/usr/lib64/python3.6/site-packages/servo/data/fpmcu_dev_board_common_inas.xml, None, 0) 2023-02-03 15:05:30,649 - SystemConfig - INFO - Loading XML config (/usr/lib64/python3.6/site-packages/servo/data/ina2xx.xml, None, 0) 2023-02-03 15:05:30,650 - SystemConfig - INFO - Loading XML config (/usr/lib64/python3.6/site-packages/servo/data/servo_fpmcu_dev_board_uart_common_overlay.xml, None, 0) 2023-02-03 15:05:30,655 - Servod - INFO - Initializing interface 1 to stm32_uart 2023-02-03 15:05:30,655 - Interface.Build - INFO - Suart: interface: {'name': 'stm32_uart', 'interface': 0, 'index': 1} 2023-02-03 15:05:30,661 - Interface.Build - INFO - /dev/pts/2 2023-02-03 15:05:30,661 - Servod - INFO - Initializing interface 2 to stm32_i2c 2023-02-03 15:05:30,661 - Interface.Build - INFO - Si2cBus: interface: {'name': 'stm32_i2c', 'interface': 4, 'index': 2} 2023-02-03 15:05:30,661 - root - INFO - Skipping modprobe of i2c-dev: it is already loaded per existence of: /sys/module/i2c_dev/ 2023-02-03 15:05:30,661 - root - INFO - Executing command: ['modprobe', '--quiet', '--', 'i2c-pseudo'] 2023-02-03 15:05:30,664 - i2c_base - INFO - path b'/dev/i2c-pseudo-controller' not found, cannot start I2C pseudo adapter 2023-02-03 15:05:30,665 - Servod - INFO - Initializing interface 3 to stm32_uart 2023-02-03 15:05:30,666 - Interface.Build - INFO - Suart: interface: {'name': 'stm32_uart', 'interface': 3, 'index': 3} 2023-02-03 15:05:30,670 - Interface.Build - INFO - /dev/pts/3 2023-02-03 15:05:30,670 - Servod - INFO - Initializing interface 6 to ec3po_uart 2023-02-03 15:05:30,673 - servo_micro - EC3PO Interface - INFO - -------------------- servo_micro console on: /dev/pts/4 2023-02-03 15:05:30,673 - Servod - INFO - Initializing interface 7 to stm32_uart 2023-02-03 15:05:30,673 - Interface.Build - INFO - Suart: interface: {'name': 'stm32_uart', 'interface': 6, 'index': 7} 2023-02-03 15:05:30,678 - Interface.Build - INFO - /dev/pts/6 2023-02-03 15:05:30,678 - Servod - INFO - Initializing interface 8 to stm32_uart 2023-02-03 15:05:30,679 - Interface.Build - INFO - Suart: interface: {'name': 'stm32_uart', 'interface': 5, 'index': 8} 2023-02-03 15:05:30,684 - Interface.Build - INFO - /dev/pts/7 2023-02-03 15:05:30,684 - Servod - INFO - Initializing interface 9 to ec3po_uart 2023-02-03 15:05:30,685 - PD/Cr50 - EC3PO Interface - INFO - -------------------- PD/Cr50 console on: /dev/pts/8 2023-02-03 15:05:30,685 - Servod - INFO - Initializing interface 10 to ec3po_uart 2023-02-03 15:05:30,687 - EC - EC3PO Interface - INFO - -------------------- EC console on: /dev/pts/10 2023-02-03 15:05:30,687 - Servod - INFO - Initializing interface 11 to ec3po_uart 2023-02-03 15:05:30,688 - CPU - EC3PO Interface - INFO - -------------------- CPU console on: /dev/pts/12 2023-02-03 15:05:31,193 - Servod - INFO - Initialized init_keyboard to on 2023-02-03 15:05:31,194 - root - WARNING - cpu_ec3po_interp_connect: '1' not found in the param values 2023-02-03 15:05:31,195 - root - WARNING - cpu_ec3po_interp_connect: update drv to get and set values from the param map {'off': '0'} 2023-02-03 15:05:31,195 - Servod - INFO - Initialized cpu_ec3po_interp_connect to off 2023-02-03 15:05:31,200 - Servod - INFO - Initialized cpu_uart_raw_debug to off 2023-02-03 15:05:31,202 - Servod - INFO - Initialized cpu_uart_timestamp to off 2023-02-03 15:05:31,204 - Servod - INFO - Initialized ec_ec3po_interp_connect to on 2023-02-03 15:05:31,205 - Servod - INFO - Initialized ec_uart_raw_debug to off 2023-02-03 15:05:31,206 - Servod - INFO - Initialized ec_uart_timestamp to on 2023-02-03 15:05:31,207 - Servod - INFO - Initialized ec_uart_flush to on 2023-02-03 15:05:31,290 - CPU - EC3PO.Console - INFO - /dev/pts/12 - Disabling uart timestamps. 2023-02-03 15:05:31,308 - Servod - INFO - Initialized uart1_en to on 2023-02-03 15:05:31,335 - Servod - INFO - Initialized servo_micro_ec_boot_mode_uut to off 2023-02-03 15:05:31,462 - Servod - INFO - Initialized servo_jtag_trst to off 2023-02-03 15:05:31,564 - Servod - INFO - Initialized spi1_buf_en to off 2023-02-03 15:05:31,664 - Servod - INFO - Initialized spi2_buf_en to off 2023-02-03 15:05:31,767 - Servod - INFO - Initialized uart2_en to on 2023-02-03 15:05:32,020 - Servod - INFO - Initialized spi1_vref to pp3300 2023-02-03 15:05:32,268 - Servod - INFO - Initialized spi2_vref to pp1800 2023-02-03 15:05:32,396 - Servod - INFO - Initialized servo_jtag_trst_dir to off 2023-02-03 15:05:32,521 - Servod - INFO - Initialized servo_jtag_tdi_dir to off 2023-02-03 15:05:32,620 - Servod - INFO - Initialized gpio_expander_reset to off 2023-02-03 15:05:32,721 - Servod - INFO - Initialized uart3_on_spi1 to off 2023-02-03 15:05:32,824 - Servod - INFO - Initialized SERVO_JTAG_TMS_DIR to off 2023-02-03 15:05:32,952 - Servod - INFO - Initialized SERVO_JTAG_TDO_SEL to off 2023-02-03 15:05:33,078 - Servod - INFO - Initialized SERVO_JTAG_TMS to off 2023-02-03 15:05:33,206 - Servod - INFO - Initialized UART3_TX_SERVO_JTAG_TCK to off 2023-02-03 15:05:33,334 - Servod - INFO - Initialized UART3_RX_JTAG_BUFFER_TO_SERVO_TDO to off 2023-02-03 15:05:33,459 - Servod - INFO - Initialized SERVO_JTAG_TDO_BUFFER_EN to off 2023-02-03 15:05:33,585 - Servod - INFO - Initialized SERVO_JTAG_TDI to off 2023-02-03 15:05:33,711 - Servod - INFO - Initialized SERVO_JTAG_RTCK to off 2023-02-03 15:05:33,808 - Servod - INFO - Initialized JTAG_BUFOUT_EN_L to off 2023-02-03 15:05:33,936 - Servod - INFO - Initialized JTAG_BUFIN_EN_L to off 2023-02-03 15:05:33,936 - Servod - INFO - Initialized usbpd_uart_routing to off 2023-02-03 15:05:33,940 - Servod - INFO - Initialized fw_wp_en to off 2023-02-03 15:05:33,943 - Servod - INFO - Initialized tp1 to off 2023-02-03 15:05:33,948 - Servod - INFO - Initialized cold_reset to off 2023-02-03 15:05:33,952 - Servod - INFO - Initialized pwr_button to release 2023-02-03 15:05:33,958 - Servod - INFO - Initialized warm_reset to on 2023-02-03 15:05:33,962 - Servod - INFO - Initialized rec_mode to on 2023-02-03 15:05:33,968 - Servod - INFO - Initialized fw_up to off 2023-02-03 15:05:33,972 - Servod - INFO - Initialized lid_open to yes 2023-02-03 15:05:33,976 - Servod - INFO - Initialized pch_disable to off 2023-02-03 15:05:33,978 - Servod - INFO - Initialized tp2 to off 2023-02-03 15:05:34,380 - servoFirmwareChecker - INFO - servo_micro firmware up to date. 2023-02-03 15:05:34,381 - Servod - INFO - Initialized servo_micro_firmware_uptodate to check 2023-02-03 15:05:34,382 - Servod - INFO - Initialized servo_ec3po_interp_connect to on 2023-02-03 15:05:34,384 - Servod - INFO - Initialized servo_micro_uart_raw_debug to off 2023-02-03 15:05:34,385 - Servod - INFO - Initialized servo_micro_uart_timestamp to on 2023-02-03 15:05:34,387 - Servod - INFO - Initialized usbpd_ec3po_interp_connect to on 2023-02-03 15:05:34,389 - Servod - INFO - Initialized jtag_vref_sel0 to pp3300 2023-02-03 15:05:34,391 - Servod - INFO - Initialized jtag_vref_sel1 to pp3300 2023-02-03 15:05:34,398 - Servod - INFO - Initialized hpd to off 2023-02-03 15:05:34,399 - Servod - INFO - Initialized fpmcu_ec3po_interp_connect to off 2023-02-03 15:05:34,401 - Servod - INFO - Initialized fpmcu_ec3po_interp_connect_1 to off 2023-02-03 15:05:34,401 - DeviceWatchdog - INFO - Watchdog setup for devices: [18d1:501a MICRO-S-2201160335] 2023-02-03 15:05:34,402 - servod - INFO - Listening on localhost port 9999 ``` In the other terminal, build and flash the firmware: Make sure the toolchain is installed: ```bash (chroot) $ sudo cros_setup_toolchains ``` Navigate to the EC source: ```bash (chroot) $ cd ../platform/ec ``` Build the firmware: ```bash (chroot) $ make BOARD= -j ``` The resulting file will be in `build//ec.bin` Flash the firmware file: ```bash (chroot) $ ./util/flash_ec --board= --image=./build//ec.bin ``` Prepare a serial terminal in your chroot: ```bash (chroot) $ sudo emerge screen ``` Connect to the UART pty: ```bash (chroot) $ sudo screen $(dut-control raw_fpmcu_console_uart_pty | cut -d: -f2) ``` Press enter key several times (may need to wait up to 20 seconds). Then you will see a prompt: ``` > ``` At this point you are connected to the MCU's serial (UART) console. You can list all of the available console commands with "help": ``` > help ``` ```bash Known commands:   chan           fpcapture      hcdebugsherase     fpenroll       history        spixfer        waitms   flashinfo      fpmatch        hostevent      sysinfo   flashread      gettime        md             sysjump   flashwp        gpioget        panicinfo      syslock   flashwrite     gpioset        reboot         taskinfo HELP LIST = more info; HELP CMD = help on CMD. ``` Start a fingerprint enrollment: ``` > fpenroll ``` ### Measuring Power {#measure-power} The Dragonclaw reference board has an onboard INA that monitors the voltage and power draw of the MCU and FP Sensor independently. Signal Name | Description --------------- | ------------------------------------- `pp3300_dx_mcu` | 3.3V supplying the MCU `pp3300_dx_fp` | 3.3V supplying the fingerprint sensor `pp1800_dx_fp` | 1.8V supplying the fingerprint sensor You can monitor all power and voltages by using the following command: ```bash (chroot) $ watch -n0.5 dut-control pp3300_dx_mcu_mv pp3300_dx_fp_mv pp1800_dx_fp_mv pp3300_dx_mcu_mw pp3300_dx_fp_mw pp1800_dx_fp_mw ``` You can get a summary of the power over `N` seconds with: ```bash (chroot) $ dut-control -t N pp3300_dx_mcu_mv pp3300_dx_fp_mv pp1800_dx_fp_mv pp3300_dx_mcu_mw pp3300_dx_fp_mw pp1800_dx_fp_mw ``` When measuring the power, make sure that any debuggers are disconnected. The most reliable way to make sure it is disconnected is to physically disconnect the debugger and servo_micro from the board. Then re-attach servo_micro and restart `servod`. *** note The `_mv` suffix denotes millivolt and `_mw` suffix denotes milliwatt. *** *** note See [Power Measurement Documentation] for more information. *** ### Toggling Hardware Write Protect When using a fingerprint development board connected to servo, you can toggle hardware write protect for testing. **NOTE**: `servod` must be running. Check the state of hardware write protect: ```bash (chroot) $ dut-control fw_wp_en ``` Enable hardware write protect: ```bash (chroot) $ dut-control fw_wp_en:on ``` Disable hardware write protect: ```bash (chroot) $ dut-control fw_wp_en:off ``` ### Contributing Changes #### Using Gerrit and git If you’re not familiar with `git`, Gerrit (code review) and `repo`, here are some docs to help you get started: * [Git and Gerrit Intro for Chromium OS]: Useful to get started as quickly as possible, but does not explain how `git` works under the hood. * [Set your editor]: Use your favorite editor when writing `git` commit messages. * [Chromium OS Contributing Guide]: Detailed overview of contributing changes to Chromium OS and the workflow we use. * [Git: Concepts and Workflow]: Good overview of how `git` actually works. * [Gerrit: Concepts and Workflow]: Good overview of how Gerrit works; assumes you understand `git` basics. * [Life of a patch]: Android workflow, but similar to ChromeOS. The Gerrit dashboard that will show your pending reviews (and ones we have for you): * [Public Gerrit] * [Internal Gerrit] #### Registering for a chromium.org *Internal* Account If your partnership agreement requires non-public code sharing you will need to register for an account on the [Internal Gerrit]. Refer to the [Gerrit Credentials Setup] page for details. Once you register for an internal account, your contact at Google can make sure you have the necessary permissions to access the private repository. *** note **NOTE**: In order to use a private repository you will have to manually add it to the repo manifest file before running `repo sync`. Check with your contact at Google for the exact values to use below: **`(outside) $ ~/chromiumos/.repo/manifests/default.xml`** ```xml ``` **`(outside) $ ~/chromiumos/.repo/manifests/remote.xml`** ```xml ``` *** ### Tracking Issues and Communication Development issue tracking and communication is done through the [Partner Issue Tracker]. You will use your [Partner Domain] account to access the [Partner Issue Tracker]. If you do not already have a [Partner Domain] account, please request one from your Google contact. In order to make sure that you receive email notifications for issues, please make sure that you [set up email forwarding] and set your [notification settings] appropriately. Communication should primarily be done through the [Partner Issue Tracker] and not email so that it can be more easily tracked by multiple people and a record is preserved for posterity. [Partner Issue Tracker]: https://developers.google.com/issue-tracker/guides/partner-access [Partner Domain]: https://developers.google.com/issue-tracker/guides/partner-domains [set up email forwarding]: https://developers.google.com/issue-tracker/guides/partner-domains#email_forwarding [notification settings]: https://developers.google.com/issue-tracker/guides/set-notification-preferences ## Working with Chromebooks Chromebooks have an FPMCU (e.g., Dragonclaw) board attached to the motherboard. You can use the device to run `ectool` commands and test the fingerprint sensor from the UI. ### Developer Mode and Write Protection Make sure that your fingerprint-equipped ChromeOS device is in [developer mode] with a *test* image flashed and [hardware write protection] disabled. Using the test image will allow you to SSH into the device and disabling hardware write protection allows you to have full access to flashing the FPMCU firmware. See [Installing Chromium] for details on flashing test images and enabling [developer mode]. ### Connecting In general, most of our development is done by connecting to the DUT (device under test) via SSH. We usually connect the DUT to ethernet (e.g., via USB-C to Ethernet converter), but WiFi should also work (assuming corporate firewall restrictions don’t block SSH port 22). To get the IP address, tap the battery/time icon in the lower right corner. Then tap on “Ethernet” followed by the gear icon in the upper right. ```bash (chroot) $ ssh root@ Password: test0000 ``` Once you have SSH’ed into the DUT, you should be able to run `ectool` commands. **Example**: Capture a "test_reset" image from the sensor and write it to a [PNM] file (viewable with the ImageMagick `display` command): ```bash (device) $ ectool --name=cros_fp fpmode capture test_reset; ectool --name=cros_fp waitevent 5 500; ectool --name=cros_fp fpframe > /tmp/test_reset.pnm ``` Alternatively, you can access a shell via the UI on device by pressing `CTRL+ALT+F2` (third key on top row). Log in with `root` and `test0000`. ### Flashing FPMCU from DUT Copy the firmware to the DUT: ```bash (chroot) $ scp ./build/bloonchipper/ec.bin :/tmp/ec.bin ``` From the DUT, flash the firmware you copied: ```bash (device) $ flash_fp_mcu /tmp/ec.bin ``` ## Commit-queue Prototype Environment ![CQ Prototype Environment] ![FPMCU devboard environment v2 with satlab] ## Troubleshooting ### Verify that servo and debugger are connected to USB {#servo-connected} Check whether servo is enumerating on USB. If you are using a debugger (Lauterbach, J-Link, etc), also check to make sure it enumerates. Depending on the debugger being used, it may need to be powered with an external power supply. ```bash (chroot) $ lsusb Bus 002 Device 003: ID 0897:0004 Lauterbach # ← This is my Lauterbach (debugger) Bus 001 Device 013: ID 18d1:5002 Google LLC # ← This is servo ``` ### "No servos found" when running servod If you get the following message, make sure that [servo is connected to USB](#servo-connected). You may also want to try restarting your machine (or VM). ```bash (chroot) $ sudo servod --board=bloonchipper 2019-04-12 14:53:42,236 - servod - INFO - Start 2019-04-12 14:53:42,270 - servod - ERROR - No servos found ``` ### Losing characters in servo UART console Make sure that this interface is disabled: ```bash (chroot) $ dut-control usbpd_ec3po_interp_connect:off ``` ### FPMCU console commands * Once the console is working you can use `help` to see the commands. * There should be fingerprint commands that start with `fp` (see `fpsensor.c` in the [EC] code). [EC]: https://chromium.googlesource.com/chromiumos/platform/ec [ectool_servo_spi]: https://chromium.googlesource.com/chromiumos/platform/ec/+/HEAD/util/comm-servo-spi.c#15 [servo]: https://chromium.googlesource.com/chromiumos/third_party/hdctools/+/HEAD/README.md [developer mode]: https://chromium.googlesource.com/chromiumos/docs/+/HEAD/debug_buttons.md#firmware-keyboard-interface [hardware write protection]: https://chromium.googlesource.com/chromiumos/platform/ec/+/HEAD/docs/write_protection.md [have the prerequisites]: https://chromium.googlesource.com/chromiumos/docs/+/HEAD/developer_guide.md#Prerequisites [get the source]: https://chromium.googlesource.com/chromiumos/docs/+/HEAD/developer_guide.md#get-the-source [enter the `chroot`]: https://chromium.googlesource.com/chromiumos/docs/+/HEAD/developer_guide.md#building-chromium-os [Chromium OS Contributing Guide]: https://chromium.googlesource.com/chromiumos/docs/+/HEAD/contributing.md [Servo Micro Info]: https://chromium.googlesource.com/chromiumos/third_party/hdctools/+/HEAD/docs/servo_micro.md [Set your editor]: https://chromium.googlesource.com/chromiumos/docs/+/HEAD/developer_guide.md#Set-your-editor [Life of a patch]: https://source.android.com/setup/contribute/life-of-a-patch [Git: Concepts and Workflow]: https://docs.google.com/presentation/d/1IQCRPHEIX-qKo7QFxsD3V62yhyGA9_5YsYXFOiBpgkk/ [Gerrit: Concepts and Workflow]: https://docs.google.com/presentation/d/1C73UgQdzZDw0gzpaEqIC6SPujZJhqamyqO1XOHjH-uk/ [Public Gerrit]: https://chromium-review.googlesource.com [Power Measurement Documentation]: https://chromium.googlesource.com/chromiumos/third_party/hdctools/+/HEAD/docs/power_measurement.md [Internal Gerrit]: https://chrome-internal-review.googlesource.com [Gerrit Credentials Setup]: https://www.chromium.org/chromium-os/developer-guide/gerrit-guide [Micro USB Cable]: https://www.monoprice.com/product?p_id=9762 [PNM]: https://en.wikipedia.org/wiki/Netpbm_format [Git and Gerrit Intro for Chromium OS]: https://chromium.googlesource.com/chromiumos/docs/+/HEAD/git_and_gerrit_intro.md [Installing Chromium]: https://chromium.googlesource.com/chromiumos/docs/+/HEAD/developer_guide.md#installing-chromium-os-on-your-device [FPMCU documentation]: ./fingerprint.md [Fingerprint Debugging]: ./fingerprint-debugging.md [dragonclaw schematics]: ../schematics/dragonclaw [Servo Micro]: ../images/servo_micro.jpg [Servo Micro with Dragonclaw]: ../images/servomicro_dragonclaw.jpg [Dragonclaw board]: ../images/dragonclaw_v0.3.jpg [Dragonclaw servo fix diagram]: ../images/dragonclaw_servo_fix.jpg [Icetower board]: ../images/icetower_v0.1.jpg [Dragonclaw Rev 0.2 1.8V Rework]: https://github.com/coreboot/chrome-ec/blob/HEAD/docs/images/dragonclaw_rev_0.2_1.8v_load_switch_rework.pdf [CQ Prototype Environment]: ../images/CQ_Prototype_Environment.jpg [FPMCU devboard environment v2 with satlab]: ../images/FPMCU_devboard_environment_v2_with_Satlab.jpg