ASCIInaut

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    ASCIInaut got a reaction from Igor in Cubietruck UART 3 4 7 Pin Out (serial, ttyS)   
    Thank you very much indeed.
     
    I was able to enable two other UARTs. After adding them to sun7i-a20-cubietruck.dts I recompiled the Kernel as suggested in http://www.armbian.com/github/. I copied the created debian packages to the Cubietruck and installed them all. This updated the Kernel to 4.2.5. UARTs are now working like a charm.
     
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    ASCIInaut reacted to zador.blood.stained in Cubietruck UART 3 4 7 Pin Out (serial, ttyS)   
    Other serial devices are not enabled in Device Tree by default, you need to modify Device Tree files and compile new dtb file to enable them.
    Starting from here 
    https://github.com/torvalds/linux/blob/master/arch/arm/boot/dts/sun7i-a20.dtsi#L1205 are sections for serial devices, common for all A20 devices, here 
    https://github.com/torvalds/linux/blob/master/arch/arm/boot/dts/sun7i-a20-cubietruck.dts#L300 uart0 is enabled. You need to add similar sections for serial devices that you want, using pinctrl parameters from here 
    https://github.com/torvalds/linux/blob/master/arch/arm/boot/dts/sun7i-a20.dtsi#L858 (which also answers your questions for pin numbers, you can check pin mappings in cubietruck schematics pdf).
    Use build script to recompile kernel (you only need new sun7i-a20-cubietruck.dtb file), adding, for example, this section to sun7i-a20-cubietruck.dts to activate uart2
    &uart2 { pinctrl-names = "default"; pinctrl-0 = <&uart2_pins_a>; status = "okay"; }; Some uarts have different pinout variants, check schematic or maybe script.fex to find correct one.
    If pinctrl section lists 4 pins instead of 2, two other pins are RTS and CTS signals, you probably won't use them.