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Fixing BLE GATT Characteristic notification and Characteristic Descriptor read #4464

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Merged
merged 3 commits into from
Nov 2, 2020
Merged

Fixing BLE GATT Characteristic notification and Characteristic Descriptor read #4464

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ee11f71
BLERemoteChar: fix descriptor 2902 write for characteristic notificat…
Oct 29, 2020
df6a2cc
BLERemoteChar: forward GATT client event to characteristic descriptors
Oct 29, 2020
b475eef
BLERemoteDescriptor: add semaphore to characteristic descriptor write
Oct 29, 2020
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11 changes: 9 additions & 2 deletions libraries/BLE/src/BLERemoteCharacteristic.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -237,6 +237,13 @@ void BLERemoteCharacteristic::gattClientEventHandler(esp_gattc_cb_event_t event,
break;
} // ESP_GATTC_WRITE_CHAR_EVT

case ESP_GATTC_READ_DESCR_EVT:
case ESP_GATTC_WRITE_DESCR_EVT:
for (auto &myPair : m_descriptorMap) {
myPair.second->gattClientEventHandler(
event, gattc_if, evtParam);
}
break;

default:
break;
Expand Down Expand Up @@ -468,7 +475,7 @@ void BLERemoteCharacteristic::registerForNotify(notify_callback notifyCallback,
if(!notifications) val[0] = 0x02;
BLERemoteDescriptor* desc = getDescriptor(BLEUUID((uint16_t)0x2902));
if (desc != nullptr)
desc->writeValue(val, 2);
desc->writeValue(val, 2, true);
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What is the reason to response await here?

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I gave the details in the commit that introduces the change. For convenience, the commit message is:

When registering a notification on a characteristic, the 2902 descriptor
(CCCD) value is set to 1 (or 2 for indication).
According to the BLUETOOTH CORE SPECIFICATION Version 5.2, Revision Date
2019-12-31, section 4.12.3 "Write Characteristic Descriptors" (page 1588),
the characteristic descriptor write must expect a response.
Currently, the descriptor write is performed without expecting a reponse,
which prevents the notification to be functional with some BLE stacks.
This commit modify the write to expect the response.

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Ok, thanks.
Commit aproved.

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Thank you.

} // End Register
else { // If we weren't passed a callback function, then this is an unregistration.
esp_err_t errRc = ::esp_ble_gattc_unregister_for_notify(
Expand All @@ -484,7 +491,7 @@ void BLERemoteCharacteristic::registerForNotify(notify_callback notifyCallback,
uint8_t val[] = {0x00, 0x00};
BLERemoteDescriptor* desc = getDescriptor((uint16_t)0x2902);
if (desc != nullptr)
desc->writeValue(val, 2);
desc->writeValue(val, 2, true);
} // End Unregister

m_semaphoreRegForNotifyEvt.wait("registerForNotify");
Expand Down
21 changes: 21 additions & 0 deletions libraries/BLE/src/BLERemoteDescriptor.cpp
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Expand Up @@ -49,6 +49,23 @@ BLEUUID BLERemoteDescriptor::getUUID() {
return m_uuid;
} // getUUID

void BLERemoteDescriptor::gattClientEventHandler(esp_gattc_cb_event_t event, esp_gatt_if_t gattc_if, esp_ble_gattc_cb_param_t* evtParam) {
switch(event) {
case ESP_GATTC_READ_DESCR_EVT:
if (evtParam->read.handle != getHandle())
break;
m_semaphoreReadDescrEvt.give();
break;

case ESP_GATTC_WRITE_DESCR_EVT:
if (evtParam->write.handle != getHandle())
break;
m_semaphoreWriteDescrEvt.give();
break;
default:
break;
}
}

std::string BLERemoteDescriptor::readValue() {
log_v(">> readValue: %s", toString().c_str());
Expand Down Expand Up @@ -137,6 +154,8 @@ void BLERemoteDescriptor::writeValue(uint8_t* data, size_t length, bool response
return;
}

m_semaphoreWriteDescrEvt.take("writeValue");

esp_err_t errRc = ::esp_ble_gattc_write_char_descr(
m_pRemoteCharacteristic->getRemoteService()->getClient()->getGattcIf(),
m_pRemoteCharacteristic->getRemoteService()->getClient()->getConnId(),
Expand All @@ -149,6 +168,8 @@ void BLERemoteDescriptor::writeValue(uint8_t* data, size_t length, bool response
if (errRc != ESP_OK) {
log_e("esp_ble_gattc_write_char_descr: %d", errRc);
}

m_semaphoreWriteDescrEvt.wait("writeValue");
log_v("<< writeValue");
} // writeValue

Expand Down
3 changes: 2 additions & 1 deletion libraries/BLE/src/BLERemoteDescriptor.h
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Expand Up @@ -35,7 +35,7 @@ class BLERemoteDescriptor {
void writeValue(std::string newValue, bool response = false);
void writeValue(uint8_t newValue, bool response = false);
void setAuth(esp_gatt_auth_req_t auth);

void gattClientEventHandler(esp_gattc_cb_event_t event, esp_gatt_if_t gattc_if, esp_ble_gattc_cb_param_t* evtParam);

private:
friend class BLERemoteCharacteristic;
Expand All @@ -49,6 +49,7 @@ class BLERemoteDescriptor {
std::string m_value; // Last received value of the descriptor.
BLERemoteCharacteristic* m_pRemoteCharacteristic; // Reference to the Remote characteristic of which this descriptor is associated.
FreeRTOS::Semaphore m_semaphoreReadDescrEvt = FreeRTOS::Semaphore("ReadDescrEvt");
FreeRTOS::Semaphore m_semaphoreWriteDescrEvt = FreeRTOS::Semaphore("WriteDescrEvt");
esp_gatt_auth_req_t m_auth;


Expand Down