Serial connection seems to broke after a few seconds

[danielk117]

Hey guys,

I just bought a ZHWG11LM and want to flash it with your OpenWRT. I tried to gain root access, following your guide. So I added my CH340 to GND, TX and RX.

When starting the device, I can see it booting. I'm able to interupt it by pressing any key and after this i see the =>. I'm able to type or paste the setenv ... for around 1 second and than the device doesn't react on my input anymore. Also, I can no longer read the output. There are just some unknown symbols (like if you use a wrong baudrate, but I use baudrate 115200).

If I'm fast, I'm able to paste the whole setenv command and press enter. The last thing I could read is NAND read .... If I don't interrupt the boot, the same thing happen. Around 1 second after the short countdown there are just unreadable symbols. I tried it with screen and minicom an macOS and PuTTY on Windows. All with the same CH340 adapter. Same thing. The CH340 should be ok, just flashed a nodeMCU with it a week ago.

Any ideas what I'm doing wrong? 😞 If you want to see a screenshot of my output, I paste it later that day when back at home.

[danielk117]

The longest output I got so far... After output stops: the RX and TX LEDs on CH340 keeps flashing fast, so there a communication!?

U-Boot 2016.03 (Nov 07 2017 - 20:11:55 +0800)

CPU:   Freescale i.MX6ULL rev1.0 528 MHz (running at 396 MHz)
CPU:   Commercial temperature grade (0C to 95C) at 35C
Reset cause: POR
Board: Lumi international Gateway
I2C:   ready
DRAM:  256 MiB
NAND:  256 MiB
MMC:   FSL_SDHC: 0, FSL_SDHC: 1
*** Warning - bad CRC, using default environment

Display: TFT43AB (480x272)
Video: LCDIF@0x21c8000 is fused, disable it
In:    serial
Out:   serial
Err:   serial
Net:   Ethernet@0x20b4000 is fused, disable it
Board Net Initialization Failed
No ethernet found.

## Enter main_loop() Now##
Normal Boot
Hit any key to stop autoboot:  0

NAND read: device 0 offset 0x300000, size 0x700000
 7340032 bytes read: OK

NAND read: device 0 offset 0xa00000, size 0x100000
 1048576 bytes read: OK
Kernel image @ 0x80800000 [ 0x000000 - 0x617290 ]
## Flattened Device Tree blob at 83000000
   Booting using the fdt blob at 0x83000000
   Using Device Tree in place at 83000000, end 8300c0e1
Modify /soc/aips-bus@02000000/tsc@02040000:status disabled
Modify /soc/aips-bus@02000000/can@02090000:status disabled
Modify /soc/aips-bus@02000000/can@02094000:status disabled
Modify /soc/aips-bus@02100000/lcdif@021c8000:status disabled
Modify /soc/aips-bus@02100000/pxp@021cc000:status disabled
Modify /soc/aips-bus@02100000/csi@021c4000:status disabled
Modify /soc/aips-bus@02000000/ethernet@020b4000:status disabled
Modify /soc/aips-bus@02100000/usb@02184200:status disabled
Modify /soc/aips-bus@02000000/spba-bus@02000000/sai@0202c000:status disabled
Modify /soc/aips-bus@02000000/spba-bus@02000000/sai@02030000:status disabled
Modify /soc/aips-bus@02100000/serial@021f4000:status disabled
Modify /soc/aips-bus@02100000/serial@021fc000:status disabled
Modify /soc/aips-bus@02000000/spba-bus@02000000/serial@02018000:status disabled
Modify /soc/aips-bus@02000000/pwm@020f0000:status disabled
Modify /soc/aips-bus@02000000/pwm@020f4000:status disabled
Modify /soc/aips-bus@02000000/pwm@020f8000:status disabled
Modify /soc/aips-bus@02000000/pwm@020fc000:status disabled
Modify /soc/aips-bus@02000000/spba-bus@02000000/ecspi@02010000:status disabled
Modify /soc/aips-bus@02000000/spba-bus@02000000/ecspi@02014000:status disabled
Modify /soc/aips-bus@02100000/i2c@021a8000:status disabled
Modify /soc/aips-bus@02100000/i2c@021f8000:status disabled
Modify /soc/aips-bus@02000000/gpt@020e8000:status disabled
Modify /soc/aips-bus@02000000/epit@020d4000:status disabled
ft_system_setup for mx6
No PMIC found!

Starting kernel ...

[    0.000000] Booting Linux on physical CPU 0x0
[    0.000000] Linux version 4.1.15+gb63f3f5 (chenlong@gitlab) (gcc version 5.3.0 (GCC) ) #37 SMP PREEMPT Tue Jun 19 15:28:38 CST 2018
[    0.000000] CPU: ARMv7 Processor [410fc075] revision 5 (ARMv7), cr=10c53c7d
[    0.000000] CPU: PIPT / VIPT nonaliasing data cache, VIPT aliasing instruction cache
[    0.000000] Machine model: Freescale i.MX6 ULL 14x14 EVK Board
[    0.000000] Reserved memory: failed to allocate memory for node 'linux,cma'
[    0.000000] cma: Reserved 96 MiB at 0x8a000000
[    0.000000] Memory policy: Data cache writealloc
[    0.000000] PERCPU: Embedded 12 pages/cpu @89da3000 s16908 r8192 d24052 u49152
[    0.000000] Built 1 zonelists in Zone order, mobility grouping on.  Total pages: 65024
[    0.000000] Kernel command line: console=ttymxc0,115200 ubi.mtd=3 root=ubi0:rootfs rootfstype=ubifs cma=96M mtdparts=gpmi-nand:3m(boot),7m(kernel),1m(dtb),-(rootfs)
[    0.000000] PID hash table entries: 1024 (order: 0, 4096 bytes)
[    0.000000] Dentry cache hash table entries: 32768 (order: 5, 131072 bytes)
[    0.000000] Inode-cache hash table entries: 16384 (order: 4, 65536 bytes)
[    0.000000] Memory: 148920K/262144K available (8035K kernel code, 423K rwdata, 2812K rodata, 540K init, 426K bss, 14920K reserved, 98304K cma-reserved, 0K highmem)
[    0.000000] Virtual kernel memory layout:
[    0.000000]     vector  : 0xffff0000 - 0xffff1000   (   4 kB)
[    0.000000]     fixmap  : 0xffc00000 - 0xfff00000   (3072 kB)
[    0.000000]     vmalloc : 0x90800000 - 0xff000000   (1768 MB)
[    0.000000]     lowmem  : 0x80000000 - 0x90000000   ( 256 MB)
[    0.000000]     pkmap   : 0x7fe00000 - 0x80000000   (   2 MB)
[    0.000000]     modules : 0x7f000000 - 0x7fe00000   (  14 MB)
[    0.000000]       .text : 0x80008000 - 0x80aa01f8   (10849 kB)
[    0.000000]       .init : 0x80aa1000 - 0x80b28000   ( 540 kB)
[    0.000000]       .data : 0x80b28000 - 0x80b91fa0   ( 424 kB)
[    0.000000]        .bss : 0x80b94000 - 0x80bfeb5c   ( 427 kB)
[    0.000000] SLUB: HWalign=64, Order=0-3, MinObjects=0, CPUs=1, Nodes=1
[    0.000000] Preemptible hierarchical RCU implementation.
[    0.000000]  Additional per-CPU info printed with stalls.
[    0.000000]  RCU restricting CPUs from NR_CPUS=4 to nr_cpu_ids=1.
[    0.000000] RCU: Adjusting geometry for rcu_fanout_leaf=16, nr_cpu_ids=1
[    0.000000] NR_IRQS:16 nr_irqs:16 16
[    0.000000] mxc_clocksource_init 24000000
[    0.000000] Switching to timer-based delay loop, resolution 41ns
[    0.000015] sched_clock: 32 bits at 24MHz, resolution 41ns, wraps every 89478484971ns
[    0.000055] clocksource mxc_timer1: mask: 0xffffffff max_cycles: 0xffffffff, max_idle_ns: 79635851949 ns
[    0.002581] Console: colour dummy device 80x30
[    0.002622] Calibrating delay loop (skipped), value calculated using timer frequency.. 48.00 BogoMIPS (lpj=240000)
[    0.002657] pid_max: default: 32768 minimum: 301
[    0.002881] Mount-cache hash table entries: 1024 (order: 0, 4096 bytes)
[    0.002912] Mountpoint-cache hash table entries: 1024 (order: 0, 4096 bytes)
[    0.004264] CPU: Testing write buffer coherency: ok
[    0.004746] /cpus/cpu@0 missing clock-frequency property
[    0.004788] CPU0: thread -1, cpu 0, socket 0, mpidr 80000000
[    0.004893] Setting up static identity map for 0x80008280 - 0x800082d8
[    0.041166] Brought up 1 CPUs
[    0.041204] SMP: Total of 1 processors activated (48.00 BogoMIPS).
[    0.041225] CPU: All CPU(s) started in SVC mode.
[    0.042322] devtmpfs: initialized
[    0.064029] VFP support v0.3: implementor 41 architecture 2 part 30 variant 7 rev 5
[    0.064918] clocksource jiffies: mask: 0xffffffff max_cycles: 0xffffffff, max_idle_ns: 19112604462750000 ns
[    0.072766] pinctrl core: initialized pinctrl subsystem
[    0.075443] NET: Registered protocol family 16
[    0.093466] DMA: preallocated 256 KiB pool for atomic coherent allocations
[    0.120873] cpuidle: using governor ladder
[    0.150938] cpuidle: using governor menu
[    0.193633] hw-breakpoint: found 5 (+1 reserved) breakpoint and 4 watchpoint registers.
[    0.193669] hw-breakpoint: maximum watchpoint size is 8 bytes.
[    0.196884] imx6ul-pinctrl 20e0000.iomuxc: Invalid fsl,pins property in node /soc/aips-bus@02000000/iomuxc@020e0000/imx6ul-evk/hoggrp-1
[    0.197588] imx6ul-pinctrl 20e0000.iomuxc: initialized IMX pinctrl driver
[    0.198273] imx6ul-pinctrl 2290000.iomuxc-snvs: initialized IMX pinctrl driver
[    0.258308] mxs-dma 1804000.dma-apbh: initialized
[    0.264941] SCSI subsystem initialized
[    0.266373] usbcore: registered new interface driver usbfs
[    0.266571] usbcore: registered new interface driver hub
[    0.266802] usbcore: registered new device driver usb
[    0.269325] i2c i2c-0: IMX I2C adapter registered
[    0.269371] i2c i2c-0: can't use DMA
[    0.270933] i2c i2c-1: IMX I2C adapter registered
[    0.270976] i2c i2c-1: can't use DMA
[    0.271276] Linux video capture interface: v2.00
[    0.271506] pps_core: LinuxPPS API ver. 1 registered
[    0.271530] pps_core: Software ver. 5.3.6 - Copy�

[devbis]

Check your soldering, wires, and uart adapter. One of these seems inapropriate

[danielk117]

Tried new wires and soldered them. Same problem. Ordered a new adapter now...

[danielk117]

New adapter, same result. Since it was never my intention, I did not try to connect with Mi Home app or HomeKit before. Tried it now and it doesn‘t work. Resetting doesn’t work either.

So soldering, wires and adapter seems to be ok. The gateway is garbage... ☹️

[devbis]

There can be many reasons that lead to this behavior. Try another desktop/laptop, try to shorten the wires.

[danielk117]

Read my first post. I was trying on windows and macOS before. Wires are already short.

I‘m not able to pair it with the xiaomi app. Resetting with holding the button for 10s doesn‘t work. I could try any wire-adapter-laptop-combination, the device itself seems to be damaged. I will replace it by a new one...

[devbis]

Okay, that is a good decision. There is a large percentage of broken devices.