updating manufacturer data in BLEAdvertisementData instance - impossible?

[mhaberler]

I'm building a sensor which reports in the manufacturer data
hence the manufacturer data changes frequently

this does work, however only on a fresh instance of BLEAdvertisementData():

  advData = new BLEAdvertisementData();
  advData->setManufacturerData(manufacturerData);

  pAdvertising->setAdvertisementData(*advData);
  pAdvertising->setAdvertisementType(BLE_GAP_CONN_MODE_NON);

  pAdvertising->start();
  delete advData;

reusing the same BLEAdvertisementData() fails - I think the payload is only appended to and there is no way to reset the payload
my solution deletes and re-creates objects needlessly

Am I overlooking something?

if not: can I suggest a BLEAdvertisementData.reset() method which resets the payload?

thanks for a great and well supported library!

Michael

repo: https://github.com/mhaberler/flowsensor/blob/main/src/beacon.cpp#L45-L55

[h2zero]

Hi @mhaberler, yes that is a deficiency in the class and a reset method should definitely be implemented. Thanks for creating this issue.

[mhaberler]

would you accept a PR? if so, on which branch - master?

[h2zero]

Yes, feel free to submit a PR to the release/1.4 branch. I will add it to the master branch after.

[mhaberler]

there is something else fishy in the code I quoted:

if I call this code too frequently (for instance from a UI button pressed in rapid succession), I get a crash

it seems I try to fiddle the advertising before the previous fiddle has finished/synced to the host

is there any predicate I can test to prevent this?

  #0  0x403769ed:0x3fcf27c0 in panic_abort at /Users/mah/.platformio/packages/framework-espidf/components/esp_system/panic.c:408
  #1  0x4037fa6d:0x3fcf27e0 in esp_system_abort at /Users/mah/.platformio/packages/framework-espidf/components/esp_system/esp_system.c:137
  #2  0x403878d1:0x3fcf2800 in __assert_func at /Users/mah/.platformio/packages/framework-espidf/components/newlib/assert.c:85
  #3  0x40386a5f:0x3fcf2920 in tlsf_free at /Users/mah/.platformio/packages/framework-espidf/components/heap/heap_tlsf.c:964 (discriminator 1)
  #4  0x40387484:0x3fcf2940 in multi_heap_free_impl at /Users/mah/.platformio/packages/framework-espidf/components/heap/multi_heap.c:225
  #5  0x403778d2:0x3fcf2960 in heap_caps_free at /Users/mah/.platformio/packages/framework-espidf/components/heap/heap_caps.c:361
  #6  0x40387901:0x3fcf2980 in free at /Users/mah/.platformio/packages/framework-espidf/components/newlib/heap.c:39
  #7  0x4207afed:0x3fcf29a0 in operator delete(void*) at /builds/idf/crosstool-NG/.build/HOST-x86_64-apple-darwin12/xtensa-esp32s3-elf/src/gcc/libstdc++-v3/libsupc++/del_op.cc:49
  #8  0x42000189:0x3fcf29c0 in __gnu_cxx::new_allocator<char>::deallocate(char*, unsigned int) at /Users/mah/.platformio/packages/toolchain-xtensa-esp32s3/xtensa-esp32s3-elf/include/c++/8.4.0/ext/new_allocator.h:125
      (inlined by) std::allocator_traits<std::allocator<char> >::deallocate(std::allocator<char>&, char*, unsigned int) at /Users/mah/.platformio/packages/toolchain-xtensa-esp32s3/xtensa-esp32s3-elf/include/c++/8.4.0/bits/alloc_traits.h:462
      (inlined by) std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >::_M_destroy(unsigned int) at /Users/mah/.platformio/packages/toolchain-xtensa-esp32s3/xtensa-esp32s3-elf/include/c++/8.4.0/bits/basic_string.h:226
      (inlined by) std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >::_M_dispose() at /Users/mah/.platformio/packages/toolchain-xtensa-esp32s3/xtensa-esp32s3-elf/include/c++/8.4.0/bits/basic_string.h:221
      (inlined by) std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >::~basic_string() at /Users/mah/.platformio/packages/toolchain-xtensa-esp32s3/xtensa-esp32s3-elf/include/c++/8.4.0/bits/basic_string.h:657
      (inlined by) NimBLEAdvertisementData::~NimBLEAdvertisementData() at lib/esp-nimble-cpp/src/NimBLEAdvertising.h:50
      (inlined by) beacon_update_manufacturer_data(unsigned char*, unsigned int) at src/beacon.cpp:49
  #9  0x420008ac:0x3fcf2a00 in sensor_update(bool) at src/main.cpp:147
  #10 0x420009a4:0x3fcf2a20 in setup()::{lambda()#2}::_FUN() at src/main.cpp:113
      (inlined by) _FUN at src/main.cpp:114
  #11 0x420582cf:0x3fcf2a40 in timer_process_alarm at /Users/mah/.platformio/packages/framework-espidf/components/esp_timer/src/esp_timer.c:360
  #12 0x42058325:0x3fcf2a70 in timer_task at /Users/mah/.platformio/packages/framework-espidf/components/esp_timer/src/esp_timer.c:386 (discriminator 1)
  #13 0x40382fd5:0x3fcf2a90 in vPortTaskWrapper at /Users/mah/.platformio/packages/framework-espidf/components/freertos/port/xtensa/port.c:142

[mhaberler]

if I may tack on a question (is there a better venue like a forum?):

is the approach "stop advertising", "fiddle manufacturer data", "restart advertising" the right one, or is there some more elegant method I overlooked?

thanks in advance
Michael

[h2zero]

The approach is correct in that the advertising should be stopped, data updated, then restarted. The issue here is that the stop process takes some time to complete and you need to wait for that before changing data.

[mhaberler]

for my understanding - would this fix the race?

• add a advCompleteCB callback to pAdvertising->start();

• if there is new advertising data, stop the scan with pAdvertising->reset() and return

• in the advCompleteCB callback, set advData->setManufacturerData(manufacturerData)

• and pAdvertising->start(..., advCompleteCB);

edit: it seems not, because pAdvertising->reset() does not trigger the advCompleteCB callback

edit2: it seems this has done the trick: https://github.com/mhaberler/flowsensor/blob/main/src/beacon.cpp#L41-L52

[h2zero]

That should be the process, looks good to me.

[mhaberler]

thanks!
leaving this open until I have a reset() method PR and the eventual working code can be referred to