How about

content_length = -1 But the content length is not -1, its 40 They're different things. esp_http_client_get_content_length is the value parsed from the Content-Length header. If the server doesn't provide this, as is the case with your link, it will return -1. You should revisit the example because ...

Use any http traffic monitor and you'll see that it is: Transfer-Encoding: chunked (with no "Content-Length" header) esp_http_client_get_content_length(client) should be returning -1 for chunked. No problem there. esp_http_client_fetch_headers(client) should be returning 0 for chunked... after calli...

I (3374) INFO: HTTP_EVENT_ON_DATA, len=40 If you're referring to this, that value is the number of bytes received and ready for your app to process from that chunk, not the value of the content length header (and not necessarily the total length). It happens to be equivalent to the total length in ...

It's definitely possible. If you look at the datasheet, especially the c reference driver, its data output is very simple and will be easy to bitbang. Of course writing the ULP program is still going to be a bit of work. I got halfway through writing a library to make this stuff easier but haven't w...

The AP interface needs to have started before configuring it. To test if this is the problem, add a delay after mode(WIFI_AP). A better solution will be to call config() on the WIFI_EVENT_AP_START event.

What is the actual voltage on the battery, under load?

It hasn't been mentioned much for some reason but the recent IDF update has significantly improved connection speeds. It was consistently taking 1100-1300ms to connect to my home WPA2 network a couple weeks ago, but in testing this week I'm consistently getting about 500ms now (often ~400ms). I have...

https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Content-Disposition I think you're using AsyncWebServer so your handler might look something like this: AsyncWebServerResponse *response = request->beginResponse(200, "text/plain", "My file contents"); response->addHeader("Content-Disposition...

Isn't this line wrong? For "spiffs.bin", indexOf("spiffs")==0 so it won't be detected as U_SPIFFS type.
Try