Difference between revisions of "Serial debugging:Cable schematics"

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Some phones have a serial port accessible from the outside, this makes debugging boot problems way easier since you can see the boot messages from the bootloader and the early kernel stuff. For example the whole nexus range has serial debugging through the headphone jack.
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This page contains schematics for serial cables, as well as device support tables and basic build instructions. For more information about serial debugging, visit the [[Serial debugging]] page.
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<!--Note to editors: if you're adding a new debug cable design/schematic for a particular device, put it at the bottom of the page. If it's a design for multiple devices or a series of devices, put it under the SuzyQ cable.-->
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 +
== microUSB/Carkit debug cable ==
 +
 
 +
Many devices with microUSB ports have the serial port multiplexed with the micro/mini USB connector, initially implemented as part of [[Micro-USB_Interface_Controller|carkit standard]]. The Replicant project has a [https://redmine.replicant.us/projects/replicant/wiki/SamsungSerial page dedicated to serial on Galaxy Nexus] using this cable.
 +
 
 +
[[File:Nexus-usb-debug.png|border|700px]]
 +
 
 +
NOTE: "TX" and "RX" on this image refer to the TX and RX pins on your UART board.
 +
 
 +
Note that some devices and [[MUIC|MUICs]] require a resistor with a different resistance than 150KΩ. '''To find the correct resistor value''', check your device's wiki page, the [[MUIC]] page or follow the guide in [[Serial_debugging#Finding_the_UART_ports_on_your_device|Serial debugging#Finding the UART ports on your device]].
 +
 
 +
{{note|'''Tip:''' Most common resistance values used for serial debugging can only be found on SMD (surface-mounted) resistors. If you want to use them with a regular breadboard, or without having to make your own PCB, you have multiple options:
 +
 
 +
* Use multiple regular resistors connected in series. There's usually a small margin of error where MUICs will detect the resistance even if it's a bit off.
 +
* [https://learn.adafruit.com/smt-prototyping-using-breakout-pcbs Use a prototyping breakout board.]
 +
* Solder wires directly to the surface-mounted resistor. This is quite challenging, as these elements are very small, and should be seen as a last resort.}}
  
 
== Nexus debug cable ==
 
== Nexus debug cable ==
  
The nexus phones multiplexed the serial debug lines with the headphone audio lines. To switch it into serial mode you have to supply -3V to the mic port. The uart lines themselves are 1.8V. If you use a 3.3V usb-to-uart adapter the signal from the phone will probably work, for the TX side you have to add a resistor divider to lover the voltage for the phone. Here's the schematic for a nexus debug cable:
+
Some Nexus phones, as well as Pixel phones with headphone jacks, multiplexed the serial debug lines with the headphone audio lines. To switch it into serial mode you have to supply -3V to the mic port. The UART lines themselves are 1.8V. If you use a 3.3V usb-to-uart adapter the signal from the phone will probably work, for the TX side you have to add a resistor divider to lower the voltage for the phone. Here's the schematic for a Nexus debug cable:
  
 
[[File:Nexus-debug-cable.png]]
 
[[File:Nexus-debug-cable.png]]
Line 9: Line 26:
 
This cable has been tested with:
 
This cable has been tested with:
  
* Nexus 5 (hammerhead)
+
* [[Google Nexus 5 (lg-hammerhead)]]
* Nexus 5X (bullhead)
+
* [[Google Nexus 5X (lg-bullhead)]]
* Pixel (sailfish)
+
* [[Google Pixel (google-pixel)]]
* Nexus 9 (flounder)
+
* [[Google Nexus 9 (htc-flounder)]]
  
 
It should work fine with:
 
It should work fine with:
  
 
* Nexus 7 2013 (flo)
 
* Nexus 7 2013 (flo)
 +
* Google Pixel 3a and 3a XL (sargo/bonito)
 +
* Google Pixel 4a (sunfish)
 +
* Google Pixel 4a 5G (bramble)
  
 
The Nexus 7 2012 (grouper) does not work with this setup and likely does not have any serial UART capabilities at all.
 
The Nexus 7 2012 (grouper) does not work with this setup and likely does not have any serial UART capabilities at all.
Line 22: Line 42:
 
Google open sourced their own [https://android.googlesource.com/device/google/debugcable/+/master debug cable design] in the AOSP repository.
 
Google open sourced their own [https://android.googlesource.com/device/google/debugcable/+/master debug cable design] in the AOSP repository.
  
== USB debug cable ==
+
NT: You will have a better luck with FTDI based serial cable.
 +
 
 +
== Mediatek USB debug cable ==
 +
 
 +
Some Mediatek devices expose an 3.3V uart interface at the usb port when a special Mediatek debug cable is attached to the device while booting
 +
 
 +
The schematic for this debug cable is the same as the Nexus USB debug cable above, except that the ID pin shouldn't be connected.
 +
 
 +
== Suzy-Q debug cable ==
 +
 
 +
The Suzy-Q debug cable isn't strictly a serial debug cable, it accesses the Closed Case Debugging system, it can access multiple busses on the device. This system was originally developed to debug chromebooks but has been used in the newer Pixel phones. Details for the Closed Case Debugging system can be found at
 +
https://chromium.googlesource.com/chromiumos/platform/ec/+/cr50_stab/docs/case_closed_debugging.md
 +
 
 +
{{todo|The usb type-c receptacle pinout is wrong(B8 is SBU2 B5 is CC2, no RFU1), see https://en.wikipedia.org/wiki/USB-C}}
 +
[[File:suzyq-debug-cable.png|600x600px]]
 +
 
 +
The official SuzyQable from Google has an 2 port USB hub into the cable itself, one port connects to the normal usb lines in the USB-C connector and the other port connects to the CC1/RFU1 pair like the diagram above, this way you can use both interfaces at the same time. The debug mode with the cable also only works on one of the two orientations in the USB-C socket. The official cable has a "DBG" mark on the C connector that should be facing up when plugged into the device. The other way around it will act as a normal USB cable.
 +
 
 +
That cable can be used with ChromeOS based devices for serial access.
  
The Nexus S, Galaxy Nexus and other many other devices have the serial port multiplexed with the micro/mini USB connector, initially implemented as part of [[Micro-USB_Interface_Controller|carkit standard]]. This is the schematic for those devices, For this cable too it's important to have a 3.3V usb-to-uart adapter.
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== Per manufacturer/series ==
  
[[File:Nexus-usb-debug.png]]
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=== Sony Xperia ===
  
It should work with:
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See [https://developer.sony.com/develop/open-devices/guides/access-uart-ports this page].
  
* Nexus S
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=== Some Motorola Devices ===
* Galaxy Nexus
 
* Samsung GT-I8190 (Galaxy S3 mini) (PMIC: AB8505)
 
* Samsung GT-I5800 (Galaxy 3) (PMIC: MAX8998)
 
* Samsung GT-P1000 (Galaxy Tab P1000)
 
* Samsung GT-S8500 (Wave)
 
* Samsung GT-S5570 (Tass) (IC: FSA9280A)
 
* Samsung i897 (Captivate)
 
* Samsung GT-i9195 (Galaxy S4 mini) (IC: TSU6721)
 
* Samsung klte (Galaxy S5)
 
* Samsung G530H (IC: SM5502)
 
* LG P700/P705 (IC: LP8727)
 
* LG P500 (IC: TS5USBA)
 
  
{| class="wikitable"
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On [https://www.manualdocelular.net/2019/01/manuais-de-servico-esquema-eletrico_25.html here], find your device, and download and extract the file,then:
  ! colspan="5" | Serial Settings
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* open the one contains schematics.
|-
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* search keyword <code>UART</code>(could be <code>MSM_UART_*</code> or <code>*_UART_MSM_*</code> or <code>*_DBG_UART_*</code>) and see where it goes to(usually it's <code>JTAG:MINI</code>).
  !  Speed  !!  Data bits  !!  Stop bits  !!  Parity  !!  Flow control
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** in some device(like <code>motorola-harpia</code>),tx and rx will connect to a test pad(<code>TP_*</code>),which makes it easier to access.
|-
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* find it in board layout and on the device.
  | 115200 || 8 || 1 || No || None
 
|}
 
  
{| class="wikitable sortable"
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== Specific devices ==
  ! rowspan="2" | Device
 
  ! rowspan="2" | Codename
 
  ! colspan="2" | Connection
 
|-
 
  !  Resistor (R3) !! Connected VCC
 
|-
 
  | style="white-space: nowrap;" | [[Google Galaxy Nexus GSM (samsung-maguro)|Google Galaxy Nexus (GSM)]]
 
  | style="white-space: nowrap;" | samsung-maguro
 
  | 619K ohm || No
 
|-
 
  | style="white-space: nowrap;" | [[Samsung Galaxy Mini 2 (samsung-s6500d)|Samsung Galaxy Mini 2]]
 
  | style="white-space: nowrap;" | samsung-s6500d
 
  | 530K ohm || No
 
|-
 
  | style="white-space: nowrap;" | [[Samsung Galaxy S4 Mini LTE]]
 
  | style="white-space: nowrap;" | samsung-i9195
 
  | 619K ohm || No
 
|-
 
  | style="white-space: nowrap;" | [[Samsung_Galaxy_S5_(samsung-klte)|Samsung Galaxy S5]]
 
  | style="white-space: nowrap;" | samsung-klte
 
  | 619K ohm || No
 
|}
 
  
== Mozilla Flame ==
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=== Mozilla Flame ===
  
 
The Flame has open UART pads that are accessible underneath the outer and inner covers.
 
The Flame has open UART pads that are accessible underneath the outer and inner covers.
Line 83: Line 85:
 
* '''GND''' - green
 
* '''GND''' - green
  
Pull-ups/downs are unneccesary, hook straight up to any FTDI/USB-to-serial.
+
Pull-ups/downs are unnecessary, hook straight up to any FTDI/USB-to-serial.
  
 
[[File:Mozilla-flame-pcb.jpg|400px]]
 
[[File:Mozilla-flame-pcb.jpg|400px]]
  
== Nokia N900 ==
+
=== Nokia N900 ===
  
 
See the following links:
 
See the following links:
Line 96: Line 98:
 
[[File:N900-serial-cable.jpg]]
 
[[File:N900-serial-cable.jpg]]
  
== Motorola Droid 4 ==
+
=== Samsung Galaxy S7 and S5 ===
 +
See [https://forum.xda-developers.com/galaxy-s7/how-to/guide-samsung-galaxy-s7-uart-t3743895 this guide]. It worked almost exactly for the S5, only kernel MUIC driver was in another directory.
 +
 
 +
=== Motorola Droid 4 ===
  
 
A off-the-shelf USB-TTL Adapter with 3.3V signal level can be used together with a MicroUSB connector to access the phone's UART. By using a standard MicroUSB &lt;-&gt; USB A cable and just combine a USB jack with a cheap chinese USB-TTL adapter is space-saving and allows you to use the same MicroUSB cable to access the device in USB mode
 
A off-the-shelf USB-TTL Adapter with 3.3V signal level can be used together with a MicroUSB connector to access the phone's UART. By using a standard MicroUSB &lt;-&gt; USB A cable and just combine a USB jack with a cheap chinese USB-TTL adapter is space-saving and allows you to use the same MicroUSB cable to access the device in USB mode
Line 103: Line 108:
 
and http://muru.com/linux/d4/
 
and http://muru.com/linux/d4/
  
== Sony Xperia ==
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=== Google Pixel "Android Debug Cable" ===
  
See [https://developer.sonymobile.com/open-devices/how-to-access-uart-ports-on-xperia-devices/ this page], and [https://developer.sony.com/develop/open-devices/guides/access-uart-ports that one] (basically a new formatting for the same page, as of 2018-02-21, but that might [https://talk.sonymobile.com/t5/General-Discussion/UART-on-Sony-Xperia-X-F5121/m-p/1302566/highlight/true#M1341 might change soon])
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While reported online that a "Suzy-Q" cable can be used for Android-based Pixel devices, the cable available from Sparkfun, the SuzyQable, is not the right cable for debugging Pixel phones. They are using a different incompatible scheme<sup>[How?]</sup>. On Pixel 2 devices they will not work at all, and on Pixel 3, it is reported they show the console of the Titan M chip only.
  
== Alternatives to a serial cable ==
+
Serial access for the Pixel 2 and 3 (unverified with 4 and 5) can instead be achieved using the following [https://github.com/Peter-Easton/android-debug-cable-howto Android Debug Cable]. Note that using a pass-through breakout board is not mandatory, but is helpful to keep the serial console active while using ADB.
There might not be a need for a serial cable if you think it is too complicated to make one for your device (although it is much more convenient when it works).
 
From [https://github.com/crondog/arch-flo there], about the [[Google Nexus 7 2013 (asus-flo)]]:
 
If you cannot get it booting you will need to reboot into recovery and check /proc/last_kmsg for the errors. Or try and build the UART cable (which I failed at)
 
  
Also, a sony employee gave an alternative method [https://talk.sonymobile.com/t5/General-Discussion/xperia-xz1-compact-boot-sequence/m-p/1274488/highlight/true#M1240 here], that might be worth a go:
+
This cable has been tested with:
Unfortunately the only way to access the serial port is to open the device but....
 
You have the other option to debug - pstore:
 
1. flash an aosp recovery image with a working kernel to the recovery partition
 
2. to flash your new kernel on the main partition and boot
 
After your new kernel crashes keep volume down pressed and you will boot the working kernel from the recovery partition. From recovery you have access to adb and you can extract the logs from pstore
 
  
== Finding the serial port on your device ==
+
* [[Google Pixel 2 XL (google-taimen)]]
Sometimes there is no other solution but to poke at random motherboard pins to find the serial port. This is mostly a lucky process, but you can:
 
* send either garbage, or a repeating pattern to the serial port at <code>/dev/ttysomething</code> (if you have a kernel where it's working), and then try to find the tx pin with a scope.
 
** If you can't, you can also reboot your phone and hope it writes something during boot (but that's really trying luck)
 
* tx is usually good enough for debugging, but rx should be quite close, with a high impedance, or more likely a pulling resistor.
 
** a pull-up or pull-down resistor will make the pin look like gnd or vcc
 
  
== Soldering a connector on your device ==
+
This cable should work fine with:
This can be a bit involved, but is generally necessary if you want to use it:
 
* This procedure is ''dangerous'' for your device, even more so if you are not very experienced
 
** Prefer to ask help in a fablab or similar ''you'll practice another day on something easier''
 
** If you have to solder it yourself, it's probably a good idea to practice on an old motherboard before
 
* Prefer soldering short cables to the PCB instead of full-length ones
 
** The smaller (diameter) the cables, the better, generally
 
** too long or too thick and the pads you have soldered risk being teared apart by the cables
 
** too small and it will be a hassle to work with
 
** The best is to have them a couple (4-8) centimeters long, to solder them, solder a connector on the other end, and scotch tape them to the pcb
 
** Please, don't forget to pick insulated wires
 
  
 +
* Google Pixel 2 (walleye)
 +
* Google Pixel 3/3 XL (blueline/crosshatch)
 +
 +
This cable might work with:
 +
 +
* Google Pixel 4/4 XL (flame/coral)
 +
* Google Pixel 5 (redfin)
  
 
== See also ==
 
== See also ==
* [[Mainlining FAQ#Serial_cable]]
+
 
* [https://code.paulk.fr/article21/a-hacker-s-journey-freeing-a-phone-from-the-ground-up-second-part exposing UART on the LG Optimus Black (P970)] (OMAP3)
+
* [[Serial debugging]]
 +
* [[Micro-USB Interface Controller]]

Revision as of 09:42, 24 February 2021

This page contains schematics for serial cables, as well as device support tables and basic build instructions. For more information about serial debugging, visit the Serial debugging page.

microUSB/Carkit debug cable

Many devices with microUSB ports have the serial port multiplexed with the micro/mini USB connector, initially implemented as part of carkit standard. The Replicant project has a page dedicated to serial on Galaxy Nexus using this cable.

Nexus-usb-debug.png

NOTE: "TX" and "RX" on this image refer to the TX and RX pins on your UART board.

Note that some devices and MUICs require a resistor with a different resistance than 150KΩ. To find the correct resistor value, check your device's wiki page, the MUIC page or follow the guide in Serial debugging#Finding the UART ports on your device.

Tip: Most common resistance values used for serial debugging can only be found on SMD (surface-mounted) resistors. If you want to use them with a regular breadboard, or without having to make your own PCB, you have multiple options:
  • Use multiple regular resistors connected in series. There's usually a small margin of error where MUICs will detect the resistance even if it's a bit off.
  • Use a prototyping breakout board.
  • Solder wires directly to the surface-mounted resistor. This is quite challenging, as these elements are very small, and should be seen as a last resort.

Nexus debug cable

Some Nexus phones, as well as Pixel phones with headphone jacks, multiplexed the serial debug lines with the headphone audio lines. To switch it into serial mode you have to supply -3V to the mic port. The UART lines themselves are 1.8V. If you use a 3.3V usb-to-uart adapter the signal from the phone will probably work, for the TX side you have to add a resistor divider to lower the voltage for the phone. Here's the schematic for a Nexus debug cable:

Nexus-debug-cable.png

This cable has been tested with:

It should work fine with:

  • Nexus 7 2013 (flo)
  • Google Pixel 3a and 3a XL (sargo/bonito)
  • Google Pixel 4a (sunfish)
  • Google Pixel 4a 5G (bramble)

The Nexus 7 2012 (grouper) does not work with this setup and likely does not have any serial UART capabilities at all.

Google open sourced their own debug cable design in the AOSP repository.

NT: You will have a better luck with FTDI based serial cable.

Mediatek USB debug cable

Some Mediatek devices expose an 3.3V uart interface at the usb port when a special Mediatek debug cable is attached to the device while booting

The schematic for this debug cable is the same as the Nexus USB debug cable above, except that the ID pin shouldn't be connected.

Suzy-Q debug cable

The Suzy-Q debug cable isn't strictly a serial debug cable, it accesses the Closed Case Debugging system, it can access multiple busses on the device. This system was originally developed to debug chromebooks but has been used in the newer Pixel phones. Details for the Closed Case Debugging system can be found at https://chromium.googlesource.com/chromiumos/platform/ec/+/cr50_stab/docs/case_closed_debugging.md

TODO The usb type-c receptacle pinout is wrong(B8 is SBU2 B5 is CC2, no RFU1), see https://en.wikipedia.org/wiki/USB-C

Suzyq-debug-cable.png

The official SuzyQable from Google has an 2 port USB hub into the cable itself, one port connects to the normal usb lines in the USB-C connector and the other port connects to the CC1/RFU1 pair like the diagram above, this way you can use both interfaces at the same time. The debug mode with the cable also only works on one of the two orientations in the USB-C socket. The official cable has a "DBG" mark on the C connector that should be facing up when plugged into the device. The other way around it will act as a normal USB cable.

That cable can be used with ChromeOS based devices for serial access.

Per manufacturer/series

Sony Xperia

See this page.

Some Motorola Devices

On here, find your device, and download and extract the file,then:

  • open the one contains schematics.
  • search keyword UART(could be MSM_UART_* or *_UART_MSM_* or *_DBG_UART_*) and see where it goes to(usually it's JTAG:MINI).
    • in some device(like motorola-harpia),tx and rx will connect to a test pad(TP_*),which makes it easier to access.
  • find it in board layout and on the device.

Specific devices

Mozilla Flame

The Flame has open UART pads that are accessible underneath the outer and inner covers.

  • TX - red
  • GND - green

Pull-ups/downs are unnecessary, hook straight up to any FTDI/USB-to-serial.

Mozilla-flame-pcb.jpg

Nokia N900

See the following links:

N900-serial-cable.jpg

Samsung Galaxy S7 and S5

See this guide. It worked almost exactly for the S5, only kernel MUIC driver was in another directory.

Motorola Droid 4

A off-the-shelf USB-TTL Adapter with 3.3V signal level can be used together with a MicroUSB connector to access the phone's UART. By using a standard MicroUSB <-> USB A cable and just combine a USB jack with a cheap chinese USB-TTL adapter is space-saving and allows you to use the same MicroUSB cable to access the device in USB mode

See http://elektranox.org/2017/02/0009-droid-4-root/ and http://muru.com/linux/d4/

Google Pixel "Android Debug Cable"

While reported online that a "Suzy-Q" cable can be used for Android-based Pixel devices, the cable available from Sparkfun, the SuzyQable, is not the right cable for debugging Pixel phones. They are using a different incompatible scheme[How?]. On Pixel 2 devices they will not work at all, and on Pixel 3, it is reported they show the console of the Titan M chip only.

Serial access for the Pixel 2 and 3 (unverified with 4 and 5) can instead be achieved using the following Android Debug Cable. Note that using a pass-through breakout board is not mandatory, but is helpful to keep the serial console active while using ADB.

This cable has been tested with:

This cable should work fine with:

  • Google Pixel 2 (walleye)
  • Google Pixel 3/3 XL (blueline/crosshatch)

This cable might work with:

  • Google Pixel 4/4 XL (flame/coral)
  • Google Pixel 5 (redfin)

See also