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Denis 'GNUtoo' Carikli, 03/10/2020 04:21 PM

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h1. UART
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There is an in-depth article covering several Samsung devices in the [[SamsungSerial]] page
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h2. Settings
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|_. Device and documentation |_. I/O voltage |_. ID<->GND |_. SOC TX |_. SOC RX |_. switch |_. stock bootloader settings |_. Comments |
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| GT-I9000 | 1.8V[8] ? | 150k | D- | D+ | | *UART settings*: 115200 8N1
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To get a shell in the bootloader:
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* Power off the phone
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* Start sending some characters through the UART
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* Press the volume down button and the power button to power up the phone
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* Release the buttons when the phone has powered up
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* Once you get the shell, you can stop sending characters through the UART | At some point the boot procedure switches to the modem UART, it's probably some linux driver doing that |
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| GT-I9100 | 1.8V[8] ? | 510k[9] | D- | D+ | "MAX8997":https://git.replicant.us/replicant/kernel_samsung_smdk4412/tree/arch/arm/configs/lineageos_i9100_defconfig#n1294 | *UART settings*: ttySAC2 115200 8N1 
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 To get the UART enabled at boot with the stock bootloader:
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* Power the phone off and remove the battery
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* Put a battery in
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* Hold the select button
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* Plug the UART
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* Release the select button
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To get the UART enabled at boot with the Replicant 6.0 kernel and the stock bootloader, see the "DHylands_SGS2_Console":https://wiki.mozilla.org/DHylands_SGS2_Console page on the mozilla wiki. | At some point the boot procedure switches to the modem UART, it's probably some linux driver doing that |
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| GT-N7000 | 1.8V[8] ? | 510k[9] | D- | D+ | | *UART settings*: 115200 8N1 | |
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| GT-I9100G_CHN_CHN | 1.8V[8] ? | 619k[9] | 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 |
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| GT-I9300 |/2. 1.8V[1] |/4. 619 kOhms[3] |/4. D- |/4. D+ |/4. MAX77693[5] |/4. *UART settings*: 115200
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To increase verbosity during boot:
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* Power off the phone and remove the battery
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* Put a battery in
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* Press the hold the volume-down button
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* Plug the UART and wait for the first lines to be printed
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* Release the volume-down button |/2. It gives a shell once Replicant 6 has booted |
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| GT-I9305 |
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| GT-N7100 | ? | |
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| GT-N7105 | ? | |
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| [[GalaxyNexusI9250SerialConsole|Galaxy Nexus (GT-I9250)]] | | 619 kOhms[4] | D+ | D- | FSA9480[7] | UART settings:
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* By default: ttyFIQ0, 115200 8N1
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* After patching Linux: ttyO2, 115200 8N1
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See [[GalaxyNexusI9250SerialConsole]] for more details. | |
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| [[NexusSI902xSerial|Nexus S]] | | 150 kOhm | | | FSA9480 | | |
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| [[OptimusBlackSerial|Optimus Black (P970)]] | 1.8V[6] | N/A[2] | | | DP3T | | |
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| ODROID-U3, console UART | 1.8V |\4. "connector":https://wiki.odroid.com/accessory/development/usb_uart_kit#odroid_port_description_of_uart_connector | *UART settings*: ttySAC1, 115200 8N1 | |
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| ODROID-U3, IO pins UART | 1.8V |\4. "connector":https://wiki.odroid.com/old_product/odroid-x_u_q/odroid_u3/u3_ioport_uart | *UART settings*: ttySAC0, 115200 8N1 | |
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fn1. Measured between USB GND and USB VCC
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fn2. Code is required to use the switch as you need to configure both the MUIC and DP3T switch
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fn3. See "The related driver source code":https://git.replicant.us/replicant/kernel_samsung_smdk4412/tree/drivers/misc/max77693-muic.c#n102
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fn4. See the "postmarketOS wiki page on Serial debugging":https://wiki.postmarketos.org/wiki/Serial_debugging
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fn5. See the "driver":https://git.replicant.us/replicant/kernel_samsung_smdk4412/tree/drivers/misc/max77693-muic.c and the "ifixit teardown":https://www.ifixit.com/Teardown/Samsung+Galaxy+S+III+Teardown/9391
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fn6. Reference: [[OptimusBlackSerial]]
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fn7. See "board-tuna-connector.c":https://git.replicant.us/replicant/kernel_samsung_tuna/tree/arch/arm/mach-omap2/board-tuna-connector.c "fsa9480.c":https://git.replicant.us/replicant/kernel_samsung_tuna/tree/drivers/misc/fsa9480.c in "kernel_samsung_tuna":https://git.replicant.us/replicant/kernel_samsung_tuna
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fn8. Works, as it was tested on the device. TODO: measure the voltage, as lower UART voltages often works with higher voltage levels.
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fn9. Works, as it was tested on the device. TODO: look the official reference in the driver for it.
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h2. Datasheets
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* "FSA9480.pdf":https://media.digikey.com/pdf/Data%20Sheets/Fairchild%20PDFs/FSA9480.pdf
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h2. Interesting links
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* There is a "page on Serial debugging":https://wiki.postmarketos.org/wiki/Serial_debugging on the postmarketOS wiki that contains information for using the serial port for many smartphones models.
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* "mv-uart":https://osmocom.org/projects/mv-uart/wiki A serial port adapter with configurable voltages (and GPIOs)
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* "DHylands_SGS2_SerialAdapter":https://wiki.mozilla.org/DHylands_SGS2_SerialAdapter : A very compact setup but with fixed resistor value.
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h2. See also
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* [[BootloaderInterfaces]]: Documentation about the stock bootloaders interfaces