UART1 (Pin 8,10 @J41) <> UHF RFID

Robotics & Edge Computing Jetson & Embedded Systems Jetson Nano
1

Hello there,

Though my problem doesn’t look new, but none of the tricks seems working for me. I tried the same with a cellular modem over UART but didn’t succeed. Then as a new start, I am now trying to connect a RFID reader module over UART1 on J41 of the board.

I am using Jetson nano development kit -A02. Trying using /dev/ttyTHS1 but no success.

  1. sudo chmod 777 /dev/ttyTHS1 - already done
  2. For ref, Pin 8 and 10 pull down (GND) using 10K resistance.
  3. sudo systemctl disable nvgetty.service - already done

Everything works well if use a FTDI and connect the same module to Nano USB port. Any pointers would help.

Regards
RR

3

hello rajat.ratra,

there’re 3 UARTs supported on Nano platform.
UART0 on the M.2 Key.
UART1 at J41 40-pin connector.
UART2 for debug, only Tx and Rx available.

please also refer to Jetson Nano Product Design Guide, J41 is by default a UART serial console.
To use UART2 for no debug use-case, just remove console-port from the kernel device tree. you should also check Topic 109102 for details.
thanks

4

Thanks JerryChang

Will try UART2 as suggested and report in case I am not able to resolve.

5

Below is the dmesg output. I may need your help for step by step process to remove console-port line from the dts file, as i am not so familiar

bcil_iot@bciliot-desktop:~$ dmesg | grep tty
[ 0.000000] Kernel command line: tegraid=21.1.2.0.0 ddr_die=2048M@2048M section=256M memtype=0 vpr_resize usb_port_owner_info=0 lane_owner_info=0 emc_max_dvfs=0 touch_id=0@63 video=tegrafb no_console_suspend=1 console=ttyS0,115200n8 debug_uartport=lsport,4 earlyprintk=uart8250-32bit,0x70006000 maxcpus=4 usbcore.old_scheme_first=1 core_edp_mv=1125 core_edp_ma=4000 gpt tegra_fbmem=0x800000@0x92ca9000 is_hdmi_initialised=1 earlycon=uart8250,mmio32,0x70006000 root=/dev/mmcblk0p1 rw rootwait rootfstype=ext4 console=ttyS0,115200n8 console=tty0 fbcon=map:0 net.ifnames=0 quiet root=/dev/mmcblk0p1 rw rootwait rootfstype=ext4 console=ttyS0,115200n8 console=tty0 fbcon=map:0 net.ifnames=0
[ 0.001596] console [tty0] enabled
[ 1.089266] console [ttyS0] disabled
[ 1.089433] 70006000.serial: ttyS0 at MMIO 0x70006000 (irq = 63, base_baud = 25500000) is a Tegra
[ 1.089603] console [ttyS0] enabled
[ 1.090817] 70006040.serial: ttyTHS1 at MMIO 0x70006040 (irq = 64, base_baud = 0) is a TEGRA_UART
[ 1.091342] 70006200.serial: ttyTHS2 at MMIO 0x70006200 (irq = 65, base_baud = 0) is a TEGRA_UART

Thanks !

6

hello rajat.ratra,

please modify tegra210-porg-p3448-common.dtsi file and remove console-port from the kernel DTS;
you should also check Kernel Customization chapter to build the device tree blob, i.e. *.dtbo.
after that, please re-flash the DTB partition to update the device tree blob, you may see Flashing a Specific Partition for reference,
thanks

8

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