Hard crash running httpserver on ESP32S2

[efc]

CircuitPython version

Adafruit CircuitPython 8.2.8 on 2023-11-16; Adafruit QT Py ESP32S2 with ESP32S2

Code/REPL

# SPDX-FileCopyrightText: 2022 Dan Halbert for Adafruit Industries
#
# SPDX-License-Identifier: Unlicense

import board
import neopixel
import mdns
import socketpool
import wifi

from adafruit_httpserver import Server, Route, as_route, Request, Response, GET, POST

mdns_server = mdns.Server(wifi.radio)
mdns_server.hostname = "efcx"
mdns_server.advertise_service(service_type="_http", protocol="_tcp", port=80)

pool = socketpool.SocketPool(wifi.radio)
server = Server(pool, "/static", debug=True)

pixel = neopixel.NeoPixel(board.NEOPIXEL, 1)

@server.route("/")
def base(request: Request):
    """
    Serve a default static plain text message.
    """
    return Response(request, "Hello from the CircuitPython HTTP Server!")

# This is the simplest way to register a route. It uses the Server object in current scope.
@server.route("/change-neopixel-color", GET)
def change_neopixel_color_handler_query_params(request: Request):
    """Changes the color of the built-in NeoPixel using query/GET params."""

    # e.g. /change-neopixel-color?r=255&g=0&b=0

    r = request.query_params.get("r") or 0
    g = request.query_params.get("g") or 0
    b = request.query_params.get("b") or 0

    pixel.fill((int(r), int(g), int(b)))

    return Response(request, f"Changed NeoPixel to color ({r}, {g}, {b})")

# This is another way to register a route. It uses the decorator that converts the function into
# a Route object that can be imported and registered later.
@as_route("/change-neopixel-color/form-data", POST)
def change_neopixel_color_handler_post_form_data(request: Request):
    """Changes the color of the built-in NeoPixel using POST form data."""

    data = request.form_data  # e.g. r=255&g=0&b=0 or r=255\r\nb=0\r\ng=0
    r, g, b = data.get("r", 0), data.get("g", 0), data.get("b", 0)

    pixel.fill((int(r), int(g), int(b)))

    return Response(request, f"Changed NeoPixel to color ({r}, {g}, {b})")

def change_neopixel_color_handler_post_json(request: Request):
    """Changes the color of the built-in NeoPixel using JSON POST body."""

    data = request.json()  # e.g {"r": 255, "g": 0, "b": 0}
    r, g, b = data.get("r", 0), data.get("g", 0), data.get("b", 0)

    pixel.fill((r, g, b))

    return Response(request, f"Changed NeoPixel to color ({r}, {g}, {b})")

# You can always manually create a Route object and import or register it later.
# Using this approach you can also use the same handler for multiple routes.
post_json_route = Route(
    "/change-neopixel-color/json", POST, change_neopixel_color_handler_post_json
)

def change_neopixel_color_handler_url_params(
    request: Request, r: str = "0", g: str = "0", b: str = "0"
):
    """Changes the color of the built-in NeoPixel using URL params."""

    # e.g. /change-neopixel-color/255/0/0

    pixel.fill((int(r), int(g), int(b)))

    return Response(request, f"Changed NeoPixel to color ({r}, {g}, {b})")

# Registering Route objects
server.add_routes(
    [
        change_neopixel_color_handler_post_form_data,
        post_json_route,
        # You can also register a inline created Route object
        Route(
            path="/change-neopixel-color/<r>/<g>/<b>",
            methods=GET,
            handler=change_neopixel_color_handler_url_params,
        ),
    ]
)

server.serve_forever(str(wifi.radio.ipv4_address))

Behavior

Auto-reload is off.
Running in safe mode! Not running saved code.

You are in safe mode because:
CircuitPython core code crashed hard. Whoops!
Hard fault: memory access or instruction error.

NeoPixel on board flashing three times every second or so.

Description

I left this code (pretty much just sample code) running on the board overnight while attached to my computer via USB. I was able to visit the website a few times (just going to root). But in the morning I found the board in safe mode with this message on the serial panel of mu.

Additional information

I have no idea if the httpserver just crashed after some period of time or if the Mac did something to kill the attached board.

Generally, how long and adafruit_httpserver servers run without cycling the board? If the board does need to be reset every now and then for stability, how often do you recommend doing that?

[dhalbert]

You may not be able to try this, but do you see the same crashes when you don't use mDNS?

[efc]

Good question, Dan. Since this crash took overnight to manifest, it will take a while to test this out.

I plan to try running this code as-is, but attaching the board to a power supply instead of a computer to see if that resolves the problem. If it does not, then I will try removing the mDNS element from the code. That is a "would-be-nice" but not essential element of the project I envision, so I can live without it.

[efc]

OK, I have run two tests with the board plugged into a power supply instead of the computer. Both failed.

In the first test I left the code as it was with mDNS above. This test ran for about 36 hours with a loop on another computer using the board's webserver to change the neopixel color every minute.

In the second test I commented out the mDNS lines. This one failed after about 90 minutes.

I doubt that the length of time between failures indicates very much, but the failure itself is a concern. In both cases the board failed with the same triple flashing of the neopixel I describe above, which I believe indicates it entered safe mode.

I am not terribly surprised that the adafruit_httpserver is not very robust. I have had similar issues with past approaches to running web servers on microcontrollers. I guess in addition to just raising the issue and hoping the software can be improved, I am wondering two things: (1) Is there anything else I can do to produce more helpful diagnostic information for anyone who might be able to improve the server, and (2) can anyone suggest code I could add to either sense failure and restart the server or to cycle the server or microcontroller in some way that might at least bring it back to life after a failure?

[anecdata]

The most immediate help is to use a safemode.py file: https://learn.adafruit.com/circuitpython-safe-mode

There are many other things that can be done for general robustness of circuit python projects. The Adafruit Discord server is a great place to ask about circuit python usage and customization.

[efc]

@anecdata, thank you for suggesting safemode.py. I have created the following safemode.py script and the devices I am testing have now been up for nearly 3 days. In those three days I have detected at least 4 crashes into safe mode, but the device has reset itself and continued on with the task.

import microcontroller
microcontroller.reset()

I would love for the wifi tools to be more stable, but this workaround at least keeps us up and on the network. Thank you!

[seandepagnier]

I managed to hit "Hard fault: memory access or instruction error." after only a few minutes playing with the httpserver examples. I dont have more details at this time, just that I was using the pico w.