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Some phones 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.<!--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.--> == microUSB/Carkit debug cable == Many devices with microUSB ports have a the serial port accessible from multiplexed with the outsidemicro/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 makes debugging boot problems way easier since you can see 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 boot messages from [[MUIC]] page or follow the bootloader and guide in [[Serial_debugging#Finding_the_UART_ports_on_your_device|Serial debugging#Finding the early kernel stuffUART ports on your device]]. For example the whole nexus range has  {{note|'''Tip:''' Most common resistance values used for serial debugging through 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 headphone jacksurface-mounted resistor. This is quite challenging, as these elements are very small, and should be seen as a last resort.}}
== Nexus debug cable ==
The nexus 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 Nexus debug cable:
[[File:Nexus-debug-cable.png]]
This cable has been tested with:
* [[Google Nexus 5 (lg-hammerhead)]]* [[Google Nexus 5X (lg-bullhead)]]* [[Google Pixel (sailfishgoogle-pixel)]]* [[Google Nexus 9 (htc-flounder)]]
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.
NT: You will have a better luck with FTDI based serial cable.
== Mediatek USB debug cable ==
The Nexus S, Galaxy Nexus and other many other Some Mediatek 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, <s>For this cable too it's important to have a expose an 3.3V usb-to-uart adapter.</s> It's not known whether interface at the different ICs do level conversion, but if they don't, the voltage would be determined by the SoC's specs (e.g 1.8v for msm8916). For safety, don't transmit usb port when a special Mediatek debug cable is attached to the device with 3.3v UART. It seems you can receive just fine though (tested with raspberry pi zero). If you have a multimeter, it might be nice to make a list of 100% known device+voltage pairs. (I don't have one, so I have to play it safe)while booting
[[File:The schematic for this debug cable is the same as the Nexus-usb-USB debugcable above, except that the ID pin shouldn't be connected.png]]
It should work with:== Suzy-Q debug cable ==
* Nexus S* Galaxy Nexus* Samsung GTThe Suzy-I8190 (Galaxy S3 mini) (PMIC: AB8505)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 * Samsung GT-I5800 (Galaxy 3) (PMIChttps: MAX8998)* Samsung GT-P1000 (Galaxy Tab P1000)* Samsung GT-S8500 (Wave)* Samsung GT-S5570 (Tass) (IC: FSA9280A)* Samsung GT-I8530 (Galaxy Beam)* [[Samsung Galaxy S III mini (samsung-golden)]]* [[Samsung Galaxy Xcover 2 (samsung-skomer)]]* Samsung i897 (Captivate)* Samsung GT-i9195 (Galaxy S4 mini) (IC: TSU6721)* [[Samsung Galaxy S5 (samsung-klte)]]* Samsung G530H (IC: SM5502)* LG P700/P705 (IC: LP8727)* LG P500 (IC: TS5USBA)/chromium.googlesource.com/chromiumos/platform/ec/+/cr50_stab/docs/case_closed_debugging.md
{{todo| class="wikitable"The usb type-c receptacle pinout is wrong(B8 is SBU2 B5 is CC2, no RFU1), see https://en.wikipedia.org/wiki/USB-C}} ! colspan="5" | Serial Settings|[[File:suzyq- ! Speed !! Data bits !! Stop bits !! Parity !! Flow control|debug- | 115200 || 8 |cable.png| 1 || No || None|}600x600px]]
{| class="wikitable sortable" ! rowspan="2" | Device ! rowspan="2" | Codename ! colspan="2" | Connection|- ! Resistor (R3) !! Connected VCC|- | style="white-space: nowrap;" | [[The official SuzyQable from 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 has an 2 (samsungport USB hub into the cable itself, one port connects to the normal usb lines in the USB-s6500d)|Samsung Galaxy Mini 2]] | style="whiteC 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-space: nowrap;C socket. The official cable has a " | samsung-s6500d | 530K ohm || No|- | style=DBG"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|- | style="white-space: nowrap;" | [[Samsung_Galaxy_Note_3_(samsung-hlte)|Samsung Galaxy Note 3]] | style="white-space: nowrap;" | samsung-hlte | 619K ohm || No|- | style="white-space: nowrap;" | [[Samsung Galaxy S III mini (samsung-golden)]] | style="white-space: nowrap;" | samsung-golden | 619K ohm || No|- | style="white-space: nowrap;" | [[Samsung Galaxy Xcover 2 (samsung-skomer)]] | style="white-space: nowrap;" | samsung-golden | 619K ohm || No|- | style="white-space: nowrap;" | [[Samsung_Galaxy_Note_8mark on the C connector that should be facing up when plugged into the device.0_(Wi-Fi)_(samsung-n5110)|Samsung Galaxy Note 8The other way around it will act as a normal USB cable.0]] | style="white-space: nowrap;" | samsung-n5110 | 619K ohm || No|}
That cable can be used with ChromeOS based devices for serial access. == Per manufacturer/series == === Sony Xperia ==See [https://developer.sony.com/develop/open-devices/guides/access-uart-ports this page]. === Some Motorola Devices = Mediatek USB debug cable ==
Some Mediatek devices expose an 3On [https://www.3V uart interface at manualdocelular.net/2019/01/manuais-de-servico-esquema-eletrico_25.html here], find your device, and download and extract the file,then:* open the usb port when one contains schematics.* 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>).** in some device(like <code>motorola-harpia</code>),tx and rx will connect to a special Mediatek debug cable is attached test pad(<code>TP_*</code>),which makes it easier to access.* find it in board layout and on 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.== Specific devices ==
=== Mozilla Flame ===
The Flame has open UART pads that are accessible underneath the outer and inner covers.
* '''GND''' - green
Pull-ups/downs are unneccesaryunnecessary, hook straight up to any FTDI/USB-to-serial.
[[File:Mozilla-flame-pcb.jpg|400px]]
=== Nokia N900 ===
See the following links:
[[File:N900-serial-cable.jpg]]
=== 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
and http://muru.com/linux/d4/
== Sony Xperia == See [https://developer.sony.com/develop/open-devices/guides/access-uart-ports this page]. == 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 Google Pixel phones. Details for the Closed Case Debugging system can be found at https://chromium.googlesource.com/chromiumos/platform/ec/+/master/docs/case_closed_debugging.md [[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. == 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<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.
Serial access for the Pixel 2 and 3 (unverified with 3a 4 and 45) 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.
This cable should work has been tested with: * Google Pixel 2* Google Pixel 3 == 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.
== Some Motorola Devices == 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:* open the one contains schematics.* 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 toGoogle Pixel 2 XL (usually it's <code>JTAG:MINI</code>).** in some device(like <code>motorolagoogle-harpia</code>taimen),tx and rx will connect to a test pad(<code>TP_*</code>),which makes it easier to access.* find it in board layout and on the device.]]
== Alternatives to a serial This cable ==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 [httpsshould work fine with://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* Google Pixel 2 (walleye)* Google Pixel 3/m-p3 XL (blueline/1274488/highlight/true#M1240 here], that might be worth a go: 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 pstorecrosshatch)
== Finding the serial port on your device ==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 cancable might work with:* 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 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 hackerspace, makerspace, 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 Google Pixel 4/4 XL (diameterflame/coral) 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 Google Pixel 5 (4-8redfin) 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
== 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)
* [[Category:GuideSerial debugging]]* [[Micro-USB Interface Controller]]
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