QUERY · ISSUE

docs: BLE Event handling seems to contradict general guidelines for IRQ handling

openby 32BTopened 2025-01-13updated 2025-11-06

docs

Documentation URL

https://docs.micropython.org/en/latest/library/bluetooth.html#event-handling

Description

In BLE event handling a suggestion is given to create copies of the ringbuffer parameters. This however, would violate the general guidelines given for interrupt routines which specifically warn against instantiating objects.
https://github.com/micropython/micropython/blob/99ac8193ea299e6d836b076149f561e58226ede6/docs/reference/isr_rules.rst?plain=1#L102

Code of Conduct

Yes, I agree

CANDIDATE · ISSUE

BLE panic in V1.19.1 but not in V1.18

closedby Tangerinoopened 2022-11-04updated 2022-11-04

bug

BLE was always working well in V1.18, handling all work inside the IRQ.
In V19.1 it starts to crash, so I made a simple program to demonstrate the issue.
I removed the code from inside the IRQ and was trying to handle the events from outside.
With this code, just connect to the device to view the problem

<details>
<summary>Sample code</summary>

from time import sleep

import ubluetooth
from machine import disable_irq
from machine import enable_irq


def register(ble):
    # Nordic UART Service (NUS)
    NUS_UUID = '6E400001-B5A3-F393-E0A9-E50E24DCCA9E'
    RX_UUID = '6E400002-B5A3-F393-E0A9-E50E24DCCA9E'
    TX_UUID = '6E400003-B5A3-F393-E0A9-E50E24DCCA9E'

    BLE_NUS = ubluetooth.UUID(NUS_UUID)
    BLE_RX = (ubluetooth.UUID(RX_UUID), ubluetooth.FLAG_WRITE)
    BLE_TX = (ubluetooth.UUID(TX_UUID), ubluetooth.FLAG_NOTIFY)

    BLE_UART = (BLE_NUS, (BLE_TX, BLE_RX,))
    SERVICES = (BLE_UART,)
    ((tx, rx,),) = ble.gatts_register_services(SERVICES)
    return tx, rx


def advertiser(ble, name):
    name = bytes(name, 'UTF-8')
    ble.gap_advertise(100, bytearray('\x02\x01\x02') + bytearray((len(name) + 1, 0x09)) + name)


ble_irq_event = -1
ble_irq_data = bytes()


def bt_irq(event, data):
    global ble_irq_event, ble_irq_data
    ble_irq_event = event
    ble_irq_data = data
    print(f"IRQ {event} - {data}")


def main():
    global ble_irq_event, ble_irq_data
    last_irq_event = -1
    last_irq_data = ble_irq_data
    ble = ubluetooth.BLE()
    ble.active(True)
    ble.irq(bt_irq)
    tx, rx = register(ble)
    advertiser(ble, "foo")
    while True:
        sleep(0.2)
        try:
            got_new_state: bool = False
            irq_state = disable_irq()
            if ble_irq_event != last_irq_event or ble_irq_data != last_irq_data:
                last_irq_event = ble_irq_event
                last_irq_data = ble_irq_data
                got_new_state = True
            enable_irq(irq_state)
            if not got_new_state:
                continue
            print(f"New event: {last_irq_event} - {last_irq_data}")
        except Exception as e:
            print(f"Error processing command - {e}")


main()

</details>

In V1.18

IRQ 1 - (0, 1, <memoryview>)
New event: 1 - (0, 1, <memoryview>)
IRQ 27 - (0, 6, 0, 500, 0)
New event: 27 - (0, 6, 0, 500, 0)
IRQ 21 - (0, 256)
IRQ 27 - (0, 36, 0, 500, 0)

In v1.19.1 (checked out few days ago)

IRQ 1 - (0, 1, <memoryview>)
Guru Meditation Error: Core  0 panic'ed (Interrupt wdt timeout on CPU0). 

Core  0 register dump:
PC      : 0x401d286e  PS      : 0x00060135  A0      : 0x800d2d9e  A1      : 0x3ffbcfb0  
A2      : 0x3ffc578c  A3      : 0x00060120  A4      : 0x8009ab14  A5      : 0x3ffbced0  
A6      : 0x00000003  A7      : 0x00060023  A8      : 0x80146bb1  A9      : 0x3ffbcfa0  
A10     : 0x00000003  A11     : 0x00060123  A12     : 0x00060120  A13     : 0x0000cdcd  
A14     : 0x00060023  A15     : 0x00060021  SAR     : 0x0000001d  EXCCAUSE: 0x00000005  
EXCVADDR: 0x00000000  LBEG    : 0x00000000  LEND    : 0x00000000  LCOUNT  : 0x00000000  


Backtrace:0x401d286b:0x3ffbcfb00x400d2d9b:0x3ffbcfd0 0x40098bc8:0x3ffbcff0