Hi Felix,

That's correct, it fails every time. When tinkering with it yesterday, I had a couple runs that actually got past the 60 second timeout, but I couldn't pin it down to a specific reason. I started digging around online about TinyGSM. They even have this in their main Github page:

"If you are able to open a TCP connection but have the connection close before receiving data, try adding a keep-alive header to your request. Some modules (ie, the SIM7000 in SSL mode) will immediately throw away any un-read data when the remote server closes the connection - sometimes without even giving a notification that data arrived in the first place. When using MQTT, to keep a continuous connection you may need to reduce your keep-alive interval (PINGREQ/PINGRESP)."

That does somewhat align with what I'm seeing. I added a .htaccess file onto the server to enable keep-alive with a pretty long interval, but it doesn't seem to have helped.

Regarding tasks, I do have it doing a few things, which I had completely working before I started on this OTA endeavour. It is an M5Stack Core with a display, an ENV III sensor, and a battery

• In setup():
• • After powering on, it checks if it is running on battery (to alert me about power outages)
• • Intialize the ENV III sensor
• • Initialize the screen
• • Initialize the modem
• In loop()
• • Update the screen
• • Get temperure/humidity readings
• • It calls a function to submit the results to my server via HTTP
• • Handle any error that the server returns, which includes it needing a firmware update. It then calls a function that has your code.
• • Then there is a while loop that runs for five minutes to watch for the buttons to be pressed.

In regards to power, the same failure occurs if it running on the internal battery or an external charger.

I think my priority here is to find a way to make the connection stay up through the 60 second barrier that seems to be imposed by the CGNAT. I am planning on deploying a number of these units, and many of the locations are rural with very poor cellular coverage, so I am expecting slow transfers. I just picked up a SIM from other carrier, which I am going to test to see if their CGNAT behaves differently.

Thanks for all your guidance!

UPDATE: Different carrier didn't have an issue with their CGNAT. I'm thinking it's because that one is a consumer service, and the one that's giving me problems is M2M specifically.

@felmue
Hi Felix!

My setup differs from yours in that I initialize the modem, do a post of data from the onboard sensors which includes the version number, then the server returns a message to it to indicate that it needs to download a firmware update. That's where I have your code run within a function instead of the main loop. So the modem already has been initialized and has working data connectivity.

I've tried a number of things over the weekend to no avail, including:

• Changing TINY_GSM_RX_BUFFER to very low values
• Reinitializing the modem within my updateFirmware function (including this step makes it almost your code verbatim)
• Removing the lte.connected() and lte.available() from the while loops

I forgot to mention, I'm downloading the same replacement firmware when I use your code and mine (it just says "It worked!" on the console), so won't contibute any differences.

@felmue Thank you so much!!! I wish I had gotten some kind of notification when you posted this! Otherwise I wouldn't have burned an entire working week of failing to get other people's libraries to work!

I loaded up your sketch and tweaked it to my modem (SIM7600) and it flawlessly downloaded a bin file and flashed it. Curiously, when I merged it into my sketch, I get the output below when trying to download the same bin file. I wonder if maybe my sketch takes up too much memory and it can't store it or something.

UPDATE 1: I did a packet capture on the web server. I can see the server transmitting the entire file, and I can see the ESP32 acknowledging the entire transmission. It's not disconnecting while downloading, so it must be something from when it goes from memory into flash. The "actually read" value does fluctuate, but is always in the range of 120000-160000.

UPDATE 2: I just noticed the duration value is always 59s +/- 0.5. With your original version, it is always 35s.

UPDATE 3: This 59s thing caught my attention. I tried switching the SIM over to another APN. The original APN uses Carrier-Grade NAT and the new one gives the modem a real public IP without any NAT. Now the new firmware downloads successfully (after around 105s). I'm guessing the 59s is actually the CGNAT timeout. That being said, I need this thing to work behind CGNAT for a few reasons. So I guess this now boils down to two questions:

• Why is my sketch taking so much longer? It's basically your script pasted into mine almost verbatim. It's exactly three times longer, curiously...
• Is there any way to decouple the flashing process from the LTE connection? I could see in my packet capture that the download completed in under one second. I'm assuming that data is stored in some sort of buffer on the modem itself. Is there a way to do something like disconnecting from the LTE but keeping the data in the buffer and letting the flash happen at its own pace? Or how do I keep the NAT translation on the LTE connection alive?

Any ideas?

Content-length: 233040
Update begin ok
Reading response data

0.00% 7.69% 15.38% 23.08% 30.77% 38.46% 46.15% 53.85% 55.73%
Error Occurred. Error #: 12

Content-Length: 233040
Actually read: 129867
Duration: 58.87s

Hi all,

I've got the ESP32 Basic Core kit and the COM.LTE module. Just wondering if anyone has has any luck in getting OTA firmware upgrades working over the LTE modem, where the ESP32 pulls the upgrade from web server. All the libraries I have found are for upgrading over wifi. And I have tried various guides that never seem to work, and most others are for pushing an update from a PC to the board.

Any help would be most appreciated!

Thanks!!