UART serial ports

Universal Asynchronous Receiver/Transmitter (UART) provides serial communication capability with external devices through a level converter and an RS-232 cable or through the use of external circuitry that converts infrared signals to electrical signals (for reception) or transforms electrical signals to signals that drive an infrared LED (for transmission) in order to provide low speed IrDA compatibility.

To see more detailed information look at the Chapter 65 on the iMX 6SoloX Reference Manual.

UDOO Neo UART ports

Table below gives a short description of the UART ports:

Name	Function	Description
UART_1	Cortex A9 serial debug	On this serial it's possible to have access to a Linux console
UART_2	Cortex M4 MQX debug	Freescale MQX real-time OS library uses this serial for debug info
UART_3	WL1831 Bluetooth chip	Used to communicate with Bluetooth chip mounted on the board
UART_4	n.c.	n.a.
UART_5	Arduino pin 0 /1 serial	It can be used by M4 microcontroller through the Serial0 object
UART_6	Cortex A9 user serial	Not enabled by default. It can be enabled on external A9 pinout

Debug UART ports

The serial debug ports (UART_1 and UART_2) are available on the external pinout. Signals can be accessed with a USB to TTL adapters.

UART 1

This UART is assigned to the A9 core as Debug Serial port. Over this serial it is possible to access a terminal console to login on a Linux shell. It can be accessed over the external pinout on the following pins:

	PCB NAME	SCHEMATICS SIGNAL NAME	SCHEMATIC IMX6 PAD NAME	REFERENCE MANUAL Pad Mux Register	ALTERNATE
UART_1_TX	47	UART1_TXD	GPIO_4	IOMUXC_SW_MUX_CTL_PAD_GPIO1_IO04	ALT0 - UART1_TX_DATA
UART_1_RX	46	UART1_RXD	GPIO_5	IOMUXC_SW_MUX_CTL_PAD_GPIO1_IO05	ALT0 - UART1_RX_DATA

Default configuration

• Baudrate: 115200
• Data: 8 bit
• Parity: none
• Stop: 1 bit
• Flow control: none
• Kernel device name: /dev/ttymxc0

UART 2

This serial is controlled by the M4 core. This core runs code based on MQX real time OS/libraries. These are a set of libraries developed by Freescale. They can exploit at best the M4 architecture, avoiding a raw port of Arduino libraries. The UART_2 port is used for debug purposes. It can be accessed over the external pinout on the following pins:

	PCB NAME	SCHEMATICS SIGNAL NAME	SCHEMATIC IMX6 PAD NAME	REFERENCE MANUAL PAD NAME	ALTERNATE
UART_2_TX	45	UART2_TXD	GPIO_6	IOMUXC_SW_MUX_CTL_PAD_GPIO1_IO06	ALT0 - UART2_TX_DATA
UART_2_RX	44	UART2_RXD	GPIO_7	IOMUXC_SW_MUX_CTL_PAD_GPIO1_IO07	ALT0 - UART2_RX_DATA

Default configuration

• Baudrate: 115200
• Data: 8 bit
• Parity: none
• Stop: 1 bit
• Flow control: none
• No kernel device (the kernel can't access this serial)

UART 3

This UART is connected to the Texas Instruments WL1831 chip for Bluetooh data communication purposes. It uses four signals at 1.8 Volts:

• RX

• TX

• CTS

• RTS

• Kernel device name: /dev/ttymxc2

	PCB NAME	SCHEMATICS SIGNAL NAME	SCHEMATIC IMX6 PAD NAME	REFERENCE MANUAL PAD NAME	ALTERNATE
UART_3_TX	-	BT_HCI_TX_1V8	SD3_DAT4	IOMUXC_SW_MUX_CTL_PAD_SD3_DATA4	ALT3 - UART3_RX_DATA
UART_3_RX	-	BT_HCI_RX_1V8	SD3_DAT5	IOMUXC_SW_MUX_CTL_PAD_SD3_DATA5	ALT3 - UART3_TX_DATA
UART_3_RTS	-	BT_HCI_RTS_1V8	SD3_DAT6	IOMUXC_SW_MUX_CTL_PAD_SD3_DATA6	ALT3 - UART3_RTS_B *
UART_3_CTS	-	BT_HCI_CTS_1V8	SD3_DAT7	IOMUXC_SW_MUX_CTL_PAD_SD3_DATA7	ALT3 - UART3_CTS_B *

* For these two signals the iMX 6Solox processor works in DCE mode.

UART 5

This is the serial controlled by the M4 core, available on the pins 0 and 1 on the external pinout. In the Arduino IDE you can access to this UART using the object Serial0.

Serial0.begin(115200); // Init the Serial at 115200 baudrate

Serial0.available(); // get the number of incoming bytes
Serial0.read(); // get the first byte in FIFO buffer

Serial0.write(); // write on output buffer byte array
Serial0.print(); // write on output buffer char array
Serial0.println(); // write on output buffer char array plus newline char

UART 6

This UART is user available, but it must be included in the device tree before the use. By default all of its pins are given to A9 in GPIO mode.

• Kernel device name: /dev/ttymxc5

	PCB NAME	SCHEMATICS SIGNAL NAME	SCHEMATIC IMX6 PAD NAME	REFERENCE MANUAL PAD NAME	ALTERNATE
UART_6_CTS_B	33	CSI0_DAT7	CSI0_DAT7	IOMUXC_SW_MUX_CTL_PAD_CSI_DATA07	ALT4 - UART6_CTS_B
UART_6_RTS_B	32	CSI0_DAT6	CSI0_DAT6	IOMUXC_SW_MUX_CTL_PAD_CSI_DATA06	ALT4 - UART6_RTS_B
UART_6_TX_DATA	31	CSI0_DAT5	CSI0_DAT5	IOMUXC_SW_MUX_CTL_PAD_CSI_DATA05	ALT4 - UART6_TX_DATA
UART_6_RX_DATA	30	CSI0_DAT4	CSI0_DAT4	IOMUXC_SW_MUX_CTL_PAD_CSI_DATA04	ALT4 - UART6_RX_DATA
UART_6_DCD_B	29	CSI0_DAT3	CSI0_DAT3	IOMUXC_SW_MUX_CTL_PAD_CSI_DATA03	ALT4 - UART6_DCD_B
UART_6_DTR_B	28	CSI0_DAT2	CSI0_DAT2	IOMUXC_SW_MUX_CTL_PAD_CSI_DATA02	ALT4 - UART6_DTR_B
UART_6_DSR_B	27	CSI0_DAT1	CSI0_DAT1	IOMUXC_SW_MUX_CTL_PAD_CSI_DATA01	ALT4 - UART6_DSR_B
UART_6_RI_B	26	CSI0_DAT0	CSI0_DAT0	IOMUXC_SW_MUX_CTL_PAD_CSI_DATA00	ALT4 - UART6_RI_B