HL7812 Modem not responding to any AT command requests

IoT Modules HL78
1

Hi,

I am working on a hl7812 modem and one of the devices stopped working without any reason. I noticed that the modem is not responding to any at commands, there is no sign that it is alive there.

I dont think there is a hardware or power supply problem.
The only thing inconsistency:
VGPIO is always high, though, GPIO6 is low

So I was using gpio6 as a low power mode indicator.

the modem software info:

HL7812.5.5.8.0-23.10.0.FreeRTOS.w41
HL78xx.5.5.8.0.RK_03_02_00_00_34211_001.20231031

Have you got any ideas on what is going on ? and How can i recover it without getting in touch with distributor?

2

Is there anything coming out in uart0 when power up?

3

i didnt have a chance to observe uart pins with an oscilloscope, but if I had anything coming out of uart0, I think I should have seen gibberish on the console screen at least. However, I observed that the CTS pin was high too.

4

from my testing, the UART0 should output some characters like this during boot up:

ÿü
NOR boot spl: Uncompressing u-boot image ... OK (141488 => 254824 55%)
Transferring control to u-boot ...
6

Hi,
Yes, i have something from UART0:

UART0 OUTPUT:

NOR boot spl: Uncompressing u-boot image ... OK (141488 => 254824 55%)
Transferring control to u-boot ...


U-Boot 2012.10 (Dec 15 2021 - 12:47:40) ALT1250_03_02_00_12_15041_UB

Board: ALT1250 Ver: 0.32-SB-E0 (PMP CPU Speed 120 MHz)
Platform id 9D9-989
DRAM:  3 MiB
Now running in RAM - U-Boot at: 902a4000
Boot mode 2
Flash Manufacturer/Device ID is: 0x20bb18
Enable QUAD mode
Flash: 16 MiB
*** Warning - Merge environment, using default environment

map import OK
USB CTRL has been successfully initialized!
In:    usbtty
Out:   usbtty
Err:   usbtty
Configuring Flash Write Protection (offset 0x192e00)
new_ce_val = 0x3a0001f0
Rst info: shutdown : power on, no reset 
Hit any key to stop autoboot:  0 
Version: 2.0

Nothing to upgrade...
hbsb ok. 194 ms 
## Starting

NOR boot spl: Uncompressing u-boot image ... OK (141488 => 254824 55%)
Transferring control to u-boot ...


U-Boot 2012.10 (Dec 15 2021 - 12:47:40) ALT1250_03_02_00_12_15041_UB

Board: ALT1250 Ver: 0.32-SB-E0 (PMP CPU Speed 120 MHz)
Platform id 9D9-989
DRAM:  3 MiB
Now running in RAM - U-Boot at: 902a4000
Boot mode 2
Flash Manufacturer/Device ID is: 0x20bb18
Enable QUAD mode
Flash: 16 MiB
*** Warning - Merge environment, using default environment

map import OK
USB CTRL has been successfully initialized!
In:    usbtty
Out:   usbtty
Err:   usbtty
Configuring Flash Write Protection (offset 0x192e00)
new_ce_val = 0x3a0001f0
Rst info: power on, no reset 
Hit any key to stop autoboot:  1 
NOR boot spl: Uncompressing u-boot image ... OK (141488 => 254824 55%)
Transferring control to u-boot ...


U-Boot 2012.10 (Dec 15 2021 - 12:47:40) ALT1250_03_02_00_12_15041_UB

Board: ALT1250 Ver: 0.32-SB-E0 (PMP CPU Speed 120 MHz)
Platform id 9D9-989
DRAM:  3 MiB
Now running in RAM - U-Boot at: 902a4000
Boot mode 2
Flash Manufacturer/Device ID is: 0x20bb18
Enable QUAD mode
Flash: 16 MiB
*** Warning - Merge environment, using default environment

map import OK
USB CTRL has been successfully initialized!
In:    usbtty
Out:   usbtty
Err:   usbtty
Configuring Flash Write Protection (offset 0x192e00)
new_ce_val = 0x3a0001f0
Rst info: shutdown : power on, no reset 
Hit any key to stop autoboot:  0 
Version: 2.0

Nothing to upgrade...
hbsb ok. 194 ms 
## Starting
7

then can you upgrade FW through UART0?

could it be soldering problem on this problematic device?

8

I have two unsuccessful attempts:

logs:

HL7812.5.5.8.0_HL78xx.5.5.8.0.RK_03_02_00_00_34211.20231031_17580_dl.txt (2.5 KB)
HL7812.5.5.8.0_HL78xx.5.5.8.0.RK_03_02_00_00_34211.20231031_16949.txt (1.9 KB)
HL7812.5.5.8.0_HL78xx.5.5.8.0.RK_03_02_00_00_34211.20231031_16949_dl.txt (2.4 KB)
HL7812.5.5.8.0_HL78xx.5.5.8.0.RK_03_02_00_00_34211.20231031_17580.txt (1.6 KB)

9

could it be soldering problem on this problematic device?

Does the download work in good device through UART0?

10

now i have the successful update but the result is still the same, the modem doesnt respond any at command over UART1.

HL7812.5.5.8.0_HL78xx.5.5.8.0.RK_03_02_00_00_34211.20231031_31044_dl.txt (11.8 KB)
HL7812.5.5.8.0_HL78xx.5.5.8.0.RK_03_02_00_00_34211.20231031_31044.txt (10.4 KB)

11

could it be soldering problem on this problematic device in uart1?

12

no im sure there is no problem with uart1. I checked again GPIO6 is low, never goes high,

13

MORE OVER UART1 CTS pin stays HIGH at all times.

14

from your UART0 boot up log:

map import OK
USB CTRL has been successfully initialized!
In:    usbtty
Out:   usbtty
Err:   usbtty

Probably you have enabled the USB port and AT port is now mapped to USB instead of UART1

15

unfortunately, it didnt work. there is no sierra wireless usb device visible when i use usb port of the modem

16

you can compare the UART0 boot up message from the good device and bad device

17

I just wanted to see the power consumption footprint, it seems it is continuously searching…
May it give some idea?

power up and first 2 mins:

image
image918×890 47.5 KB

9 mins later, after powering up

image
image950×943 137 KB

I never seen this power consumption behavior before:

first 15 secs after powering up:

image
image952×963 55.1 KB

18

you can compare the UART0 boot up message from the good device and bad device

19

one of the healthy board’s uart0 output: yes u’re right, in out is serial,

But im %100 sure i dont have circuit issue with usb comport on the bad device. it shouldve been visible when I plugged in an usb .

Even after we re burned the sw to the modem, why didnt we have serial is default? Normally, serial uart1 was always defualt on good devices.

NOR boot spl: Uncompressing u-boot image ... OK (141488 => 254824 55%)
Transferring control to u-boot ...


U-Boot 2012.10 (Dec 15 2021 - 12:47:40) ALT1250_03_02_00_12_15041_UB

Board: ALT1250 Ver: 0.32-SB-E0 (PMP CPU Speed 120 MHz)
Platform id 9D9-989
DRAM:  3 MiB
Now running in RAM - U-Boot at: 902a4000
Boot mode 2
Flash Manufacturer/Device ID is: 0x20bb18
Enable QUAD mode
Flash: 16 MiB
*** Warning - Merge environment, using default environment

map import OK
In:    serial
Out:   serial
Err:   serial
Configuring Flash Write Protection (offset 0x192e00)
new_ce_val = 0x3a00f8e0
Rst info: shutdown : power on, no reset 
Hit any key to stop autoboot:  0 
Version: 2.0

Nothing to upgrade...
hbsb ok. 194 ms 
## Starting
20

How can you confirm there is no usb circuit issue on your device?
Do you mean you have tried this in good device before?

21

yeah, i tried this switching from uart1 to usb, usb to uart1 many times by running at+usbcomp=1/0 at+cfun=1,1 , its a verified circuit.