SIM7070G firmware upgrade via modem USB not creating COM port (T-SIM7070G ESP32 board)
Shadowfader 2026-03-29 22:27:09 73 Views1 Replies SIM7070G firmware upgrade via modem USB not creating COM port (T-SIM7070G ESP32 board)
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Hello everyone,
I am trying to upgrade the firmware of the SIM7070G modem on my board, but I am running into a problem where the modem USB interface does not appear as a COM port in Windows. Because of this, the firmware upgrade tool cannot detect the modem.
I wanted to ask if anyone here has successfully upgraded the firmware of this modem or encountered the same issue.
Board information
Board used: LilyGO TTGO T-SIM7070G (ESP32 + SIM7070G modem)
Current modem firmware
I checked the modem firmware using AT commands.
AT+CGMR Revision: 1951B14SIM7070 OK
Why I am trying to upgrade the firmware
I am working on a project using this board where the modem will be used for communication (LTE-M / NB-IoT). During testing I noticed that some functionality behaves differently from the documentation, so I wanted to update the modem firmware to make sure I am running a recent and stable version.
Because of that I attempted to follow the official firmware upgrade procedure.
Documentation and guides I followed
I followed these resources carefully:
LilyGO modem upgrade guide
https://github.com/Xinyuan-LilyGO/LilyGo-Modem-Series/blob/main/docs/en/esp32/sim7000-esp32/upgrade/sim7000_upgrade.md
LilyGO T-SIM7000G firmware update documentation
https://github.com/Xinyuan-LilyGO/LilyGO-T-SIM7000G/blob/master/docs/How%20to%20update%20firmware.md
Firmware upgrade video demonstration
https://www.youtube.com/watch?v=lGctqLDGHz4
I tried to replicate the same steps shown in the documentation and video.
Steps I performed
This is exactly what I did:
Located the modem USB pads on the board.
Soldered a USB breakout cable to the modem USB pads.
Connected the modem USB directly to my PC.
Installed the USB drivers mentioned in the documentation.
Verified that Windows detects a new device when connecting the modem USB.
Opened Device Manager to check if the modem appears as a COM port.
Attempted to start the firmware upgrade tool.
What happens
Windows does detect a device when I connect the modem USB.
However, the modem does NOT appear as a serial COM port.
So the firmware upgrade tool cannot detect the modem and the upgrade cannot start.
What I already checked
USB connection works
Drivers are installed
Device appears in Windows
But no COM port is created
So it looks like the modem USB interface is detected, but not as a serial interface.
My question
Has anyone successfully upgraded the firmware of the SIM7070G on this board?
Is there something specific required to make the modem appear as a COM port, for example:
• a specific USB driver
• a required modem USB mode
• a boot or download mode for firmware upgrade
• or a hardware step specific to the T-SIM7070G board
I also opened an issue on the LilyGO GitHub repository to ask the same question, but I wanted to check here as well in case someone already solved this.
Any help would be greatly appreciated.
Thanks!
I wanted to add some context about why I am trying to upgrade the firmware on my SIM7070G module and the problem I am encountering in my project.
Project goal:
I am using a LilyGO TTGO T-SIM7070G board (ESP32 + SIM7070G) to send sensor data (P1-meter readings) via LTE-M / NB-IoT to a remote server. Reliable TCP/IP communication is critical.
Observed problem:
During testing, the SIM7070G’s internal TCP/IP stack crashes after 2–3 consecutive connections. This affects all protocols using TCP and UDP (MQTT, HTTP, raw TCP, UDP via AT commands). The module stops responding to AT commands until a full power cycle is applied. The root cause is that the module does not fully clear its internal network state after each connection, leading to RST packets, lost PDP contexts, or stalled sessions.
Why firmware upgrade:
I attempted the official firmware upgrade to see if a more recent firmware version fixes this TCP stack issue. The guides and video I followed:
LilyGO modem upgrade guide: https://github.com/Xinyuan-LilyGO/LilyGo-Modem-Series/blob/main/docs/en/esp32/sim7000-esp32/upgrade/sim7000_upgrade.md
LilyGO T-SIM7000G firmware update documentation: https://github.com/Xinyuan-LilyGO/LilyGo-T-SIM7000G/blob/master/docs/How%20to%20update%20firmware.md
Firmware upgrade video demonstration: https://www.youtube.com/watch?v=lGctqLDGHz4
Testing results so far:
USB connection works, device is detected by Windows
Drivers installed
Modem does not appear as a COM port → upgrade tool cannot detect it
Workaround in project:
Until a firmware fix is available, I implemented a hardware power cycle after each message (PWR_PIN toggle), which reliably clears the module’s TCP state. This makes end-to-end communication functional, albeit slower (~25–30s per message).
References:
External confirmation: DFRobot forum (July 2025), other developers observed the same TCP/IP crash issue in firmware 1951B14SIM7070 / 1951B15SIM7070.
Shadowfader 