UART Interfaces

The expansion board exposes two UART ports, UART_0 and UART_1, at the breakout connectors for peripheral device communications and system development activities.

UART mapping to breakout connectors

Pin #

Signal Name

Direction

Signal Description

J13.32

UART_0_CTS_LS

Input

UART port 0 clear-to-send

J13.30

UART_0_RTS_LS

Output

UART port 0 ready-to-send

J13.28

UART_0_RXD_LS

Input

UART port 0 receive data

J12.7

UART_0_TXD_LS

Output

UART port 0 transmit data

J12.24

UART_1_RXD_LS

Input

UART port 1 receive data

J12.22

UART_1_TXD_LS

Output

UART port 1 transmit data, and hardware strap. Refer to Buttons Jumpers and LEDs for strapping information.

 

The UART controllers are integrated into the module. Consult UART Interface Specifications for specific modes of operation.

UART2 of the module is dedicated to serial debug port J9 on the expansion board. See the Debug and Troubleshooting section for more information on UART2 usage.

UART Level Translation on the Expansion Board

Level translation (shifting) of the UART signals from the module native 1.8 VDC level to the expansion board is accomplished using the Texas Instruments* (TI) LSF0108RKSR device; the same device is used for other level translation activities on the expansion board. The expansion board should include appropriate pullup values to the desired voltage, but not to exceed 3.3 V.

UART Signal Termination and Conditioning

For information about signal termination and conditioning, definitions of the values in the following table, and how the values were measured, refer to Termination and Conditioning. For an example of how to wire a pullup resistor for a 3.3 V pullup voltage, refer to GPIO Signal Termination and Conditioning.

UART signal level translation termination recommendations

Signal Name

Pullup Voltage

Rmin (Ω)

CLOAD (pF)

Trise (ns)

Tfall (ns)

UART_0_CTS_LS

UART_0_RTS_LS

UART_0_RXD_LS

UART_0_TXD_LS

UART_1_RXD_LS

UART_1_TXD_LS

3.3

2400

47

36

33

 

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