ORCA SBC/Interfaces and Connectors/UARTs

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Version Issue Date Notes
1.0.0 Dec 2021 First release

UARTs interface[edit | edit source]

Description[edit | edit source]

The UARTs interfaces available on the Evaluation Kit are mapped to the following connectors:

  • J8 is a 20x2x2.54mm pin header expansion connector that delivers many interfaces unused on board. On this connector are mapped these instances: UART1; UART2 (default debug console); UART4.
UARTs J8 connector
  • J9 is a 8x1x1.25mm 53398-0871 Molex connector that delivers one RS232 4 wires (mapped to UART1) and one RS485 2 wires (mapped to UART3)
UARTs J9 connector

Signals[edit | edit source]

The following tables describe the interfaces signals:

J8[edit | edit source]

Pin# SOM Pin# Pin name Pin function Pin Notes
7 J15.150 SAI2_TXFS UART1_CTS shared with RS232
8 J15.144 SAI2_RXFS UART1_TXD shared with RS232
10 J15.140 SAI2_RXC UART1_RXD shared with RS232
11 J15.142 SAI2_RXD0 UART1_RTS shared with RS232
19 J15.122 ECSPI2_MOSI UART4_TXD Transmit signal (OUT)
21 J15.120 ECSPI2_MISO UART4_CTS Clear to send (OUT)
23 J15.124 ECSPI2_SCLK UART4_RXD Receive signal (IN)
24 J15.126 ECSPI2_SS0 UART4_RTS Request to send (IN)
27 J15.248 UART2_RXD UART2_RXD default debug console
29 J15.250 UART2_TXD UART2_TXD default debug console
31 J15.256 UART4_RXD UART4_RXD alternative to ECSPI2_SCLK
33 J15.258 UART4_TXD UART4_TXD alternative to ECSPI2_MOSI
1, 17 - 3V3_CB Power output for transceiver supply BOARD_PGOOD driven rail
6, 9, 14, 20, 25, 30, 34, 39 - DGND Ground

J9[edit | edit source]

Pin# SOM Pin# Pin name Pin function Pin Notes
1 - RS485_A Non inverting BUS signal
2 - RS485_B Inverting BUS signal
3 - RS485_B_120R Termination resistor connect this signal to RS485_B

to enable the 120R termination

4 - DGND Ground
5 J15.144 RS232_TX Transmit line shared with J8.8
6 J15.140 RS232_RX Receive line shared with J8.10
7 J15.150 RS232_CTS Clear to send line shared with J8.7
8 J15.142 RS232_RTS Request to send line shared with J8.11

Device mapping[edit | edit source]

UART1 is mapped to /dev/ttymxc0 device in Linux

UART2 is mapped to /dev/ttymxc1 device in Linux. The peripheral is used as the default serial console, both for the bootloader and the kernel.

UART3 is mapped to /dev/ttymxc2 device in Linux

UART4 is mapped to /dev/ttymxc3 device in Linux

Device usage[edit | edit source]

The TTL UARTs on J8 can be connected to external devices that use 0-3.3V levels.

The RS232 and RS485 uses the standard protocols.