OLIMEX© 2018
A20-OLinuXino-MICRO user's manual
6.1.2 UART0, UEXT1, UEXT2 interface
The UART0 might be used for UART communication by default. It is typically used for
serial/terminal debug. The UEXTs are typically used for connecting additional modules.
Note that by default only UART0 is defined as a port suitable for serial debug. You can use our
USB-SERIAL-CABLE-F for debugging. UEXT1 and UEXT2 are NOT defined by default.
Consider table below when connecting the USB-SERIAL-CABLE-F according to the wire color
code. The RX line of the cable (GREEN wire) should go to TX line of the target board; the TX line
of the cable (RED wire) should go to the RX line of the target board. The BLUE wire should go to
the target's GND line.
UART0
Pin # Signal name
Processor pin
1
3.3V
-
2
UART0-TX
A7
3
UART0-RX
B7
4
GND
-
UEXT1
Pin # Signal name
Pin # Signal name
1
3.3V
2
GND
3
UART6-TX
4
UART6-RX
5
TWI2-SCK
6
TWI2-SDA
7
SPI2-MISO
8
SPI2-MOSI
9
SPI2-CLK
10
SPI2-CS0
UEXT2
Pin # Signal name
Pin # Signal name
1
3.3V
2
GND
3
UART7-TX
4
UART7-RX
5
TWI1-SCK
6
TWI1-SDA
7
SPI1-MISO
8
SPI1-MOSI
9
SPI1-CLK
10
SPI1-CS0
The UEXT connectors are used as an interface for the Olimex's UEXT modules (usually boards
with MOD- prefix in their commercial names). For more information on UEXT please visit:
https://www.olimex.com/Products/Modules/UEXT/resources/UEXT.pdf
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