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== 3.3V vs 1.8V UARTs ==
[[File:Uart33_18_voltage_divider.png|thumb|Schematic for a 3.3v->1.8v UART voltage divider]]
Most phones expose their UART pins on 1.8V voltage, and most USB-UART converters expect UART side to have 3.3V. This works well for receiving characters from device; this is enough to read bootloader logs or kernel boot logs (dmesg). However sending 3.3V to device that expects 1.8V is dangerous; so you can't use shell over UART without an additional effort.
You'll need a voltage divider at least on converter->device TX line: use this answer https://electronics.stackexchange.com/a/333230
 
[[File:Uart33_18_voltage_divider.png]]
== See also ==
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