i.MX6Q UART and IOMux tool problem?

[andrewtrotman]

Hi,

When I use the IOMux tool (Version 3.4.0.0) to generate the code to route the pins for UART2 on the i.MX6Q (pins E25/E26) it generates the following code:

void uart2_iomux_config(void)
{
    // Config uart2.UART2_RX_DATA to pad EIM_DATA27(E25)
    HW_IOMUXC_SW_MUX_CTL_PAD_EIM_DATA27_WR(0x00000004); // DISABLED, ALT4
    // ENABLED, 100K_OHM_PU, PULL, ENABLED, DISABLED, 100MHZ, 40_OHM, SLOW
    HW_IOMUXC_SW_PAD_CTL_PAD_EIM_DATA27_WR(0x0001B0B0);
    HW_IOMUXC_UART2_UART_RX_DATA_SELECT_INPUT_WR(0x00000000); // EIM_DATA26_ALT4

    // Config uart2.UART2_TX_DATA to pad EIM_DATA26(E24)
    HW_IOMUXC_SW_MUX_CTL_PAD_EIM_DATA26_WR(0x00000004); // DISABLED, ALT4
    // ENABLED, 100K_OHM_PU, PULL, ENABLED, DISABLED, 100MHZ, 40_OHM, SLOW
    HW_IOMUXC_SW_PAD_CTL_PAD_EIM_DATA26_WR(0x0001B0B0);
    HW_IOMUXC_UART2_UART_RX_DATA_SELECT_INPUT_WR(0x00000000); // EIM_DATA26_ALT4
}

This works fine for writing to the port, but unless I add the following line:

HW_IOMUXC_UART2_UART_RX_DATA_SELECT_INPUT_WR(BF_IOMUXC_UART2_UART_RX_DATA_SELECT_INPUT_DAISY_V(EIM_DATA27_ALT4));

I can't read from the port - I don't get a signal on the RDR bit of USR2.  Adding the line fixes the problem - I can read and write to UART2.

Have I missed something here?  I've not tried it on the other UART - presumably I'll find similar problems?

[weidong_sun]

Hello,Andrew,

      EIM_D25 can be iomuxed UART3_RX_DATA, not UART2_RX. But UART2_RX can be routed throuth EIM_D27 Pin. Please Check it in I.MX6QRM.pdf , PAGE 275.

Regards,

Weidong

[YixingKong]

Weidong, since the DI's link has been messed, and we are unable to correct the error, could you finish the DI with the customer ASAP?

Thanks,

Yixing

[YixingKong]

Weidong, could you reply the customer's further issues?

Thanks,

Yixing

[andrewtrotman]

I'm not sure how that helps.  I'm trying to get UART1 and UART2 to work, I'm not using UART3.  To get UART1 to work I need to add the line:

HW_IOMUXC_UART1_UART_RX_DATA_SELECT_INPUT_WR(BF_IOMUXC_UART1_UART_RX_DATA_SELECT_INPUT_DAISY_V(SD3_DATA6_ALT1));

This appears to be because the code that the IOMux tool produces incorrectly routes.  For example, IOMux tool produces the code:

HW_IOMUXC_UART2_UART_RX_DATA_SELECT_INPUT_WR(BF_IOMUXC_UART2_UART_RX_DATA_SELECT_INPUT_DAISY_V(EIM_DATA26_ALT4));

which routes UART2_TX_DATA. The code should read:

HW_IOMUXC_UART2_UART_RX_DATA_SELECT_INPUT_WR(BF_IOMUXC_UART2_UART_RX_DATA_SELECT_INPUT_DAISY_V(EIM_DATA27_ALT4));

which routes UART2_RX_DATA.

[YixingKong]

Andrew, please click Correct Answer/Helpful Answer if your questions had been answered.

Thanks,

Yixing

[weidong_sun]

Hello,Andrew,

      Actually, UART IOMUX configuration is not idifficult , iomux tool is a way to get it , but we have another easy way to do it : open linux/arch/arm/plat-mxc/include/mach/iomux-mx6q.h, we can find all iomux definitions for pins of i.mx6Q . what we need to do is add definitions to board initialization. for example, let us do IOMUX for UART2.

(1) No.1 method:

----------------------------

MX6Q_PAD_EIM_D26__UART2_TXD      (means EIM_D26--->UART2_TX signal)

MX6Q_PAD_EIM_D27__UART2_RXD     (means EIM_D27--->UART2_RX signal)

-----------------------------

(2)No.2 method:

-------------------------------

MX6Q_PAD_GPIO_7__UART2_TXD           (means GPIO_7--->UART2_TX signal)

MX6Q_PAD_GPIO_8__UART2_RXD            (means GPIO_8--->UART2_RX signal)

--------------------------------

(3)No.3 method

----------------------------

MX6Q_PAD_SD4_DAT4__UART2_TXD      (means SD4_DAT4--->UART2_TX signal)

MX6Q_PAD_SD4_DAT7__UART2_RXD     (means SD4_DAT7--->UART2_RX signal)

----------------------------

Use any one of the above 3 groups , you can get UART2 signals. Then add them to BSP file of your board.

such as mx6q_sabresd board : open linux/arch/arm/mach-mx6/board-mx6q_sabresd.h

static iomux_v3_cfg_t mx6q_sabresd_pads[] = {

......

MX6Q_PAD_EIM_D26__UART2_TXD,

MX6Q_PAD_EIM_D27__UART2_RXD,

.......

}

Regards,

Weidong

[normancheung]

Weidong,

Could you please elaborate on why there are 3 methods.  I am facing issue with not able to write to /dev/ttymxc2, I can read.  I wonder if my PAD is set correctly.  Do these 3 methods represent 3 wiring schemes?

Thanks,

Norm

[weidong_sun]

Hi, Norman,

    Actually, there serveral methords to iomux UART2 signals, could you understand this list ?

UART2_RX and UART2_TX can be routed out via 4 different PADs. I just gave you 3 PADs of them before.

Weidong

[normancheung]

Got it, I will check with my h/ware guy to see which pin he routed the TX and the RX.

Thanks