-- add to NimbleClient.h/cpp

virtual void onPassKeyDisplay(NimBLEConnInfo& connInfo);
-- modify NimbleClient.cpp
Add the conditional statement event->passkey.params.action == BLE_SM_IOACT_DISP to the case BLE_GAP_EVENT_PASSKEY_ACTION: block in NimBLEClient::handleGapEvent().
-- add to NimbleDevice.h/cpp
static bool injectDisplayPassKey(const NimBLEConnInfo& peerInfo, uint32_t pin);

Author: inclusus

src/NimBLEClient.cpp

@@ -1304,7 +1304,7 @@ void NimBLEClientCallbacks::onPassKeyEntry(NimBLEConnInfo& connInfo) {
 void NimBLEClientCallbacks::onPassKeyDisplay(NimBLEConnInfo& connInfo) { //@@hjlee
     NIMBLE_LOGD(CB_TAG, "onPassKeyEntry: default: 123456");
     NimBLEDevice::injectDisplayPassKey(connInfo, 123456);
-} // onPassKeyEntry
+} // onPassKeyDisplay
 
 void NimBLEClientCallbacks::onAuthenticationComplete(NimBLEConnInfo& connInfo) {
     NIMBLE_LOGD(CB_TAG, "onAuthenticationComplete: default");