UART » History » Revision 59

« Previous | Revision 59/93 (diff) | Next »
Denis 'GNUtoo' Carikli, 03/08/2020 02:36 AM


There is an in-depth article covering several Samsung devices in the SamsungSerial page


Device and documentation I/O voltage ID<->GND SOC TX SOC RX switch stock bootloader settings Comments
GT-I9100 510k MAX8997 UART settings: ttySAC2 115200 8N1
To get the UART enabled at boot with the stock bootloader:
* Power the phone off and remove the battery
* Put a battery in
* Press the select button
* Plug the UART
* Stop pressing the select button
At some point the boot procedure switches to the modem UART, it's probably some linux driver doing that
GT-I9100G_CHN_CHN 1.8V8 ? 619k9 D- D+ ? UART settings: 115200 8N1 Very few prints from Xloader, the next bootloader used by Android 2.6.3 doesn't seem to print much
GT-I9300 1.8V1 619 kOhms3 D- D+ MAX776935 UART settings: 115200
* pressing the volume-down button during boot increase verbosity
It gives a shell once Replicant 6 has booted
GT-N7100 ?
GT-N7105 ?
Galaxy Nexus (GT-I9250) 619 kOhms4 D+ D- FSA94807 * By default: ttyFIQ0, 115200 8N1
* With patching: ttyO2, 115200 8N1
See GalaxyNexusI9250SerialConsole for more details.
Nexus S 150 kOhm FSA9480
Optimus Black (P970) 1.8V6 N/A2 DP3T
ODROID-U3, console UART 1.8V connector ttySAC1, 115200 8N1
ODROID-U3, IO pins UART 1.8V connector ttySAC0, 115200 8N1

1 Measured between USB GND and USB VCC

2 Code is required to use the switch as you need to configure both the MUIC and DP3T switch

3 See The related driver source code

4 See the postmarketOS wiki page on Serial debugging

5 See the driver and the ifixit teardown

6 Reference: OptimusBlackSerial

7 See board-tuna-connector.c fsa9480.c in kernel_samsung_tuna

8 Works, as it was tested on the device. TODO: measure the voltage, as lower UART voltages often works with higher voltage levels.

9 Works, as it was tested on the device. TODO: look the official reference in the driver for it.


Interesting links

  • There is a page on Serial debugging on the postmarketOS wiki that contains information for using the serial port for many smartphones models.
  • mv-uart A serial port adapter with configurable voltages (and GPIOs)
  • DHylands_SGS2_SerialAdapter : A very compact setup but with fixed resistor value.

Updated by Denis 'GNUtoo' Carikli over 4 years ago · 59 revisions

Also available in: PDF HTML TXT