DeviceInfoService leads to out of memory on ESP32 8mb/no PSRAM

[hberg32]

I've run into an out of memory error with the BLE library and while it is not a blocker for me (I can skip over it), it's weird so I thought I'd report it in case it could be of some use. I don't know how to debug circuitpython but if there is a way to increase the traceback module's "limit" param or turn on exception chaining in boot.py I can try it and report the results.

I've written a BLE parser class for the cycling power service and a simpletest that is a copy of ble_cycling_speed_and_cadence_simpletest.py but with my own service class substituted for CyclingSpeedAndCadenceService and a few prints of gc.mem_free() sprinkled about. It works fine on desktop linux. On an ESP32 8mb/no psram (product 5426) I get an out of memory error when doing if DeviceInfoService in conn:. I can only assume that there is something strange about my particular BLE device that causes something to go wrong after _discover_remote calls self._bleio_connection.discover_remote_services

I'm running the 9.2.8 bootloader with the circuitpython bundle cut on 8/7/2025

Here is the code output:

Scanning...
78064
<ProvideServicesAdvertisement flags= services=<BoundServiceList: UUID(0x1818), UUID(0x1826)> comp>
found a CyclingPowerService advertisement
<ProvideServicesAdvertisement flags= services=<BoundServiceList: UUID(0x1818), UUID(0x1826)> comp>
found a CyclingPowerService advertisement
Stopped scanning
69344
Connected 1
69120
Determining manufacturer
Traceback (most recent call last):
File "code.py", line 51, in
File "adafruit_ble/init.py", line 88, in contains
File "adafruit_ble/init.py", line 66, in _discover_remote
MemoryError: Nimble out of memory

And here is the code:

# SPDX-FileCopyrightText: 2020 Dan Halbert for Adafruit Industries
# SPDX-License-Identifier: MIT

"""
Read cycling speed and cadence data from a peripheral using the standard BLE
Cycling Speed and Cadence (CSC) Service.
"""

import time, gc

import adafruit_ble
from adafruit_ble.advertising.standard import ProvideServicesAdvertisement
from adafruit_ble.services.standard.device_info import DeviceInfoService

from cycling_power_service import CyclingPowerService

# Initialize the BLE radio
ble = adafruit_ble.BLERadio()


while True:
    print("Scanning...")
    print(gc.mem_free())
    # Save advertisements, indexed by address
    advs = {}
    for adv in ble.start_scan(ProvideServicesAdvertisement, timeout=5):
        print(adv)
        if CyclingPowerService in adv.services:
            print("found a CyclingPowerService advertisement")
            # Save advertisement. Overwrite duplicates from same address (device).
            advs[adv.address] = adv

    ble.stop_scan()
    print("Stopped scanning")
    print(gc.mem_free())
    if not advs:
        # Nothing found. Go back and keep looking.
        continue

    # Connect to all available CSC sensors.
    cyc_connections = []
    for adv in advs.values():
        cyc_connections.append(ble.connect(adv))
        print("Connected", len(cyc_connections))
        print(gc.mem_free())

    # Print out info about each sensors.
    for conn in cyc_connections:
        if conn.connected:
            print("Determining manufacturer")
            if DeviceInfoService in conn:
                dis = conn[DeviceInfoService]
                try:
                    manufacturer = dis.manufacturer
                except AttributeError:
                    manufacturer = "(Manufacturer Not specified)"
                print("Device:", manufacturer)
            else:
                print("No device information")

    print("Waiting for data... (could be 10-20 seconds or more)")
    # Get CSC Service from each sensor.
    cyc_services = []
    if len(cyc_connections) > 1:
        print("Multiple trainers detected, this implementation just grabs the first one")
    for conn in cyc_connections:
        cyc_services.append(conn[CyclingPowerService])

    # Read data from each sensor once a second.
    # Stop if we lose connection to all sensors.
    while True:
        still_connected = False
        for conn, svc in zip(cyc_connections, cyc_services):
            if conn.connected:
                still_connected = True
                print(svc.get_cycling_power_measurement)
                print(gc.mem_free())

        if not still_connected:
            break
        time.sleep(1)