Revision as of 18:10, 1 November 2018

DART-MX8M - UART

DART-MX8M UART Overview

All 4 UARTs on DART-MX8M are enabled by default. UART1 is connected to debug console, UART2 and UART3 are connected to header J12 on DART-MX8M carrier board, UART4 is connected to Bluetooth module. On DART-MX8M SoMs without WIFI/BT module UART4 is also connected to J12 header. See carrier board datasheet https://www.variscite.com/wp-content/uploads/2018/04/VAR-DT8MCustomBoard-Datasheet.pdf for the exact pinout. Only UART4 has RTS and CTS lines.

UART naming under Linux

The Linux devices corresponding to UART1 - UART4 are /dev/ttymxc0 - /dev/ttymxc3 respectively.

Testing UART2

Short J12.4 and J12.6 pins and run the following commands:

stty -F /dev/ttymxc1 -echo -onlcr 115200
cat /dev/ttymxc1 &
echo hello > /dev/ttymxc1

Each time you run echo command the "hello" string should appear on the terminal.

Testing UART3

Short J12.11 and J12.13 pins and run the following commands:

stty -F /dev/ttymxc2 -echo -onlcr 115200
cat /dev/ttymxc2 &
echo hello > /dev/ttymxc2

Each time you run echo command the "hello" string should appear on the terminal.

Disabling UART2

To disable UART2 edit arch/arm64/boot/dts/variscite/imx8m-vart-dart-common.dsti under kernel source directory and modify

&uart2 {
        ...
        status = "okay";
};

to

&uart2 {
        ...
        status = "disabled";
};

@@ Line 30: / Line 30: @@
 Each time you run echo command the "hello" string should appear on the terminal.
-= Using UART3 for console (instead of UART1) =
+= Disabling UART2 =
-In the following example we use UART3 for console.<br>
-Other UART ports can be used, similarly.<br>
-== Changes needed in U-Boot ==
+To disable UART2 edit arch/arm64/boot/dts/variscite/imx8m-vart-dart-common.dsti under kernel source directory and modify
-<syntaxhighlight lang="diff">
+<pre>
-Subject: [PATCH] mx6ul_var_dart: Use UART3 for console (instead of UART1)
+&uart2 {
+        ...
+        status = "okay";
+};
+</pre>
----
+to
- board/variscite/mx6ul_var_dart/mx6ul_var_dart.c | 8 ++++----
- include/configs/mx6ul_var_dart.h                | 4 ++--
-files changed, 6 insertions(+), 6 deletions(-)
-diff --git a/board/variscite/mx6ul_var_dart/mx6ul_var_dart.c b/board/variscite/mx6ul_var_dart/mx6ul_var_dart.c
+<pre>
-index 63a75ec..9d70851 100755
+&uart2 {
---- a/board/variscite/mx6ul_var_dart/mx6ul_var_dart.c
+        ...
-+++ b/board/variscite/mx6ul_var_dart/mx6ul_var_dart.c
+        status = "disabled";
-@@ -162,9 +162,9 @@ int dram_init(void){
+};
- }
+</pre>
--static iomux_v3_cfg_t const uart1_pads[] = {
--	MX6_PAD_UART1_TX_DATA__UART1_DCE_TX | MUX_PAD_CTRL(UART_PAD_CTRL),
--	MX6_PAD_UART1_RX_DATA__UART1_DCE_RX | MUX_PAD_CTRL(UART_PAD_CTRL),
-+static iomux_v3_cfg_t const uart3_pads[] = {
-+	MX6_PAD_UART3_TX_DATA__UART3_DCE_TX | MUX_PAD_CTRL(UART_PAD_CTRL),
-+	MX6_PAD_UART3_RX_DATA__UART3_DCE_RX | MUX_PAD_CTRL(UART_PAD_CTRL),
- };
- static iomux_v3_cfg_t const usdhc1_pads[] = {
-@@ -253,7 +253,7 @@ static void setup_gpmi_nand(void)
- static void setup_iomux_uart(void)
- {
--	imx_iomux_v3_setup_multiple_pads(uart1_pads, ARRAY_SIZE(uart1_pads));
-+	imx_iomux_v3_setup_multiple_pads(uart3_pads, ARRAY_SIZE(uart3_pads));
- }
- static struct fsl_esdhc_cfg usdhc_cfg[2] = {
-diff --git a/include/configs/mx6ul_var_dart.h b/include/configs/mx6ul_var_dart.h
-index 5313d17..88bc1a0 100755
---- a/include/configs/mx6ul_var_dart.h
-+++ b/include/configs/mx6ul_var_dart.h
-@@ -55,7 +55,7 @@
- #define CONFIG_MXC_GPIO
- #define CONFIG_MXC_UART
--#define CONFIG_MXC_UART_BASE		UART1_BASE
-+#define CONFIG_MXC_UART_BASE		UART3_BASE
- /* MMC Configs */
- #ifdef CONFIG_FSL_USDHC
-@@ -169,7 +169,7 @@
-         BOOT_ENV_SETTINGS \
- 	"script=boot.scr\0" \
- 	"image=zImage\0" \
--	"console=ttymxc0\0" \
-+	"console=ttymxc2\0" \
- 	"fdt_high=0xffffffff\0" \
- 	"initrd_high=0xffffffff\0" \
- 	"var_auto_fdt_file=Y\0" \
---
-.9.1
-</syntaxhighlight>
-You can follow the "Build U-Boot from source code" guide to get the U-Boot source code and build it.<br>
-== Changes needed in Yocto ==
-Edit the file: sources/meta-variscite-imx/conf/machine/imx6ul-var-dart.conf<br>
-and change the line:<br>
-SERIAL_CONSOLE = "115200 ttymxc0"<br>
-to:<br>
-SERIAL_CONSOLE = "115200 ttymxc2"<br>
-<br>
-(or you can change it on the target in /etc/inittab)
-= Disable the console =
-Disabling the serial console completely is not recommended, as it makes it hard or even impossible to analyze errors such as a user interface crash or to get control of the system if it doesn't boot successfully.<br>
-If you need to do it anyway, this is how.<br>
-<br>
-For Debian, the only changes needed are in U-Boot.<br>
-== Changes needed in U-Boot ==
-Applying the first patch only will still allow you to stop the boot process at U-Boot and get to the U-Boot command line.<br>
-Applying the second patch will eliminate that also.<br>
-<syntaxhighlight lang="diff">
-Subject: [PATCH 1/2] mx6ul_var_dart: Silence console
----
- board/variscite/mx6ul_var_dart/mx6ul_var_dart.c | 2 ++
- include/configs/mx6ul_var_dart.h                | 8 +++++++-
-files changed, 9 insertions(+), 1 deletion(-)
-diff --git a/board/variscite/mx6ul_var_dart/mx6ul_var_dart.c b/board/variscite/mx6ul_var_dart/mx6ul_var_dart.c
-index 59c4da7f8a..139b5bc216 100755
---- a/board/variscite/mx6ul_var_dart/mx6ul_var_dart.c
-+++ b/board/variscite/mx6ul_var_dart/mx6ul_var_dart.c
-@@ -966,8 +966,10 @@ void board_init_f(ulong dummy)
- 	/* setup GP timer */
- 	timer_init();
-+#ifndef CONFIG_SPL_NO_CONSOLE
- 	/* UART clocks enabled and gd valid - init serial console */
- 	preloader_console_init();
-+#endif
- 	setup_i2c(0, CONFIG_SYS_I2C_SPEED, 0x7f, &i2c_pad_info1);
- 	setup_i2c(1, CONFIG_SYS_I2C_SPEED, 0x7f, &i2c_pad_info2);
-diff --git a/include/configs/mx6ul_var_dart.h b/include/configs/mx6ul_var_dart.h
-index 5313d17c21..abbcb11620 100755
---- a/include/configs/mx6ul_var_dart.h
-+++ b/include/configs/mx6ul_var_dart.h
-@@ -93,6 +93,11 @@
- #define CONFIG_POWER_PFUZE3000_I2C_ADDR  0x08
- #endif
-+#define CONFIG_SYS_DEVICE_NULLDEV
-+#define CONFIG_SILENT_CONSOLE
-+#define CONFIG_SILENT_CONSOLE_UPDATE_ON_RELOC
-+#define CONFIG_SPL_NO_CONSOLE
-+
- #define CONFIG_SYS_MMC_IMG_LOAD_PART	1
- #define NAND_BOOT_ENV_SETTINGS \
-@@ -169,7 +174,8 @@
-         BOOT_ENV_SETTINGS \
- 	"script=boot.scr\0" \
- 	"image=zImage\0" \
--	"console=ttymxc0\0" \
-+	"silent=1\0" \
-+	"console=null\0" \
- 	"fdt_high=0xffffffff\0" \
- 	"initrd_high=0xffffffff\0" \
- 	"var_auto_fdt_file=Y\0" \
---
-.11.0
-</syntaxhighlight>
-<syntaxhighlight lang="diff">
-Subject: [PATCH 2/2] mx6ul_var_dart: Autoboot with no delay and no check for
- abort
----
- include/configs/mx6ul_var_common.h | 2 +-
-file changed, 1 insertion(+), 1 deletion(-)
-diff --git a/include/configs/mx6ul_var_common.h b/include/configs/mx6ul_var_common.h
-index 8556b257be..6139ec6d55 100644
---- a/include/configs/mx6ul_var_common.h
-+++ b/include/configs/mx6ul_var_common.h
-@@ -72,7 +72,7 @@
- #define CONFIG_SYS_LOAD_ADDR	CONFIG_LOADADDR
- #ifndef CONFIG_BOOTDELAY
--#define CONFIG_BOOTDELAY	1
-+#define CONFIG_BOOTDELAY	-2
- #endif
- /* allow to overwrite serial and ethaddr */
---
-.11.0
-</syntaxhighlight>
-== Changes needed in Yocto ==
-Edit the file: sources/meta-variscite-imx/conf/machine/imx6ul-var-dart.conf<br>
-and change the line:<br>
-SERIAL_CONSOLE = "115200 ttymxc0"<br>
-to:<br>
-SERIAL_CONSOLE = ""<br>
-<br>
-(or you can change it on the target in /etc/inittab)

DART-MX8M UART: Difference between revisions