Modify UART1 as DTE mode for IMX6Q using Android 4.4.2 BSP

[changyuheng]

BSP version: Android 4.4.2, kernel 3.0.35

Hello:

As title, I must be choose UART1 console debug port from DCE mode to DTE mode for my custom board,

my TX and RX and connection method as follow:

CPU            PC

TX<---------- TX

RX----------> RX

Pin difinition:

MX6Q_PAD_SD3_DAT7__UART1_TXD,

MX6Q_PAD_SD3_DAT6__UART1_RXD,

And register mapping:

#define _MX6Q_PAD_SD3_DAT6__UART1_RXD IOMUX_PAD(0x0694, 0x02AC, 1, 0x0920, 3, 0)

#define _MX6Q_PAD_SD3_DAT7__UART1_TXD IOMUX_PAD(0x0690, 0x02A8, 1, 0, 0, 0)

my modified pin definition to be DTE mode as follow:

#define _MX6Q_PAD_SD3_DAT6__UART1_RXD IOMUX_PAD(0x0694, 0x02AC, 1, 0x0920, 3, 0)

#define _MX6Q_PAD_SD3_DAT7__UART1_TXD IOMUX_PAD(0x0690, 0x02A8, 1, 0x0920, 2, 0)

but my uart1 still not work, maybe I have a wrong way to modify registers, how could I fix this issue?

thanks.

[changyuheng]

It still not work when I modify as follow:

#define _MX6Q_PAD_SD3_DAT6__UART1_RXD IOMUX_PAD(0x0694, 0x02AC, 1, 0, 0, 0)

#define _MX6Q_PAD_SD3_DAT7__UART1_TXD IOMUX_PAD(0x0690, 0x02A8, 1, 0x0920, 2, 0)

thanks

[Yuri]

IMX6 UART has some specific implementation features. The i.MX6 DQ Reference

Manual provides clear description about internal signals and (external) multiplexing
for them. Table in the Datasheet helps to clarify it. Also - the next thread in Community
may be helpful.

"i.MX6: What does the DTE/DCE in i.MX6's UART do and how are RTS and CTS affected
by the UARTxUFCR[DTEDCE] bit?"

  https://community.freescale.com/docs/DOC-97509

Have a great day,
Yuri

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