UART¶

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

Settings¶

Device and documentation	I/O voltage	ID<->GND	SOC TX	SOC RX	switch	stock bootloader settings	Comments
GT-I9100
GT-I9100G	1.8V8 ?	619k9	D-	D+	?	115200 8N1
GT-I9300	1.8V1	619 kOhms3	D-	D+	MAX776935	* speed: 115200 * pressing the volume-down button during boot increase verbosity	It gives a shell once Replicant 6 has booted
GT-I9305
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.

Datasheets¶

• FSA9480.pdf

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)