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Schematics: Console

A project log for FunKey project - All your games on your keychain !

Fun-on-a-Keychain is back, packing all your games and multiple emulators in a cute and extremely tiny handheld console.

Squonk42Squonk42 05/04/2019 at 20:340 Comments

The Allwinner V3s provides 3x UARTs (UnAsynchronous Receivers / Transmitters): UART0 with only RX and TX signals, and UART1 and UART2with additional RTS and CTS flow control signals.

As almost all SoCs, tha Allwinner V3s provides a serial console as a control terminal for debug or normal operation. By default, it is mapped to UART0, and it is used by the BROM (Boot Rom), the U-Boot bootloader and by the Linux kernel to output messages during the boot process, and later by the Linux kernel to log messages during normal operation. Depending on the configuration, it can be used too for loging into the system over an UART.

The Console schematic only requires a minimum of external components:

Besides the 3-pin 1.27 mm  (0.05") pitch header J1 that will not be mounted on standard products, there is only a single series resistor R3.

What is the purpose of this resistor?

Note that there is no ESD protection TVS diodes: this interface is not supposed to be mounted in the final user device, and PCB space is really constrained in this area, so they are omitted.

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