Introduce L2CAP infrastructure.

L2CAP is the underlying technology powering GATT.
BLE 5 exposes L2CAP COC (Connection Oriented Channels)
allowing a streaming API that leads to much higher throughputs
than you can achieve with updating GATT characteristics.

The patch follows the established infrastructure very closely.
The main components are:

- `NimBLEL2CAPChannel`, encapsulating an L2CAP COC.
- `NimBLEL2CAPServer`, encapsulating the L2CAP service.
- `Examples/L2CAP`, containing a client and a server application.

Apart from these, only minor adjustments to the existing code was
necessary.
This commit is contained in:
Dr. Michael Lauer
2025-04-28 10:54:32 -06:00
committed by Ryan Powell
parent 59e111ab55
commit e55ad9019c
22 changed files with 876 additions and 0 deletions
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.vscode
build
sdkconfig
sdkconfig.old
dependencies.lock
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# The following lines of boilerplate have to be in your project's
# CMakeLists in this exact order for cmake to work correctly
cmake_minimum_required(VERSION 3.5)
include($ENV{IDF_PATH}/tools/cmake/project.cmake)
set(SUPPORTED_TARGETS esp32 esp32s3 esp32c3 esp32c6)
project(L2CAP_client)
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PROJECT_NAME := L2CAP_client
include $(IDF_PATH)/make/project.mk
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set(COMPONENT_SRCS "main.cpp")
set(COMPONENT_ADD_INCLUDEDIRS ".")
register_component()
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#
# "main" pseudo-component makefile.
#
# (Uses default behaviour of compiling all source files in directory, adding 'include' to include path.)
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dependencies:
local/esp-nimble-cpp:
path: ../../../../../esp-nimble-cpp/
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#include <NimBLEDevice.h>
// See the following for generating UUIDs:
// https://www.uuidgenerator.net/
// The remote service we wish to connect to.
static BLEUUID serviceUUID("dcbc7255-1e9e-49a0-a360-b0430b6c6905");
// The characteristic of the remote service we are interested in.
static BLEUUID charUUID("371a55c8-f251-4ad2-90b3-c7c195b049be");
#define L2CAP_CHANNEL 150
#define L2CAP_MTU 5000
const BLEAdvertisedDevice* theDevice = NULL;
BLEClient* theClient = NULL;
BLEL2CAPChannel* theChannel = NULL;
size_t bytesSent = 0;
size_t bytesReceived = 0;
class L2CAPChannelCallbacks: public BLEL2CAPChannelCallbacks {
public:
void onConnect(NimBLEL2CAPChannel* channel) {
printf("L2CAP connection established\n");
}
void onMTUChange(NimBLEL2CAPChannel* channel, uint16_t mtu) {
printf("L2CAP MTU changed to %d\n", mtu);
}
void onRead(NimBLEL2CAPChannel* channel, std::vector<uint8_t>& data) {
printf("L2CAP read %d bytes\n", data.size());
}
void onDisconnect(NimBLEL2CAPChannel* channel) {
printf("L2CAP disconnected\n");
}
};
class MyClientCallbacks: public BLEClientCallbacks {
void onConnect(BLEClient* pClient) {
printf("GAP connected\n");
pClient->setDataLen(251);
theChannel = BLEL2CAPChannel::connect(pClient, L2CAP_CHANNEL, L2CAP_MTU, new L2CAPChannelCallbacks());
}
void onDisconnect(BLEClient* pClient, int reason) {
printf("GAP disconnected (reason: %d)\n", reason);
theDevice = NULL;
theChannel = NULL;
vTaskDelay(1000 / portTICK_PERIOD_MS);
BLEDevice::getScan()->start(5 * 1000, true);
}
};
class MyAdvertisedDeviceCallbacks: public BLEAdvertisedDeviceCallbacks {
void onResult(const BLEAdvertisedDevice* advertisedDevice) {
if (theDevice) { return; }
printf("BLE Advertised Device found: %s\n", advertisedDevice->toString().c_str());
if (!advertisedDevice->haveServiceUUID()) { return; }
if (!advertisedDevice->isAdvertisingService(serviceUUID)) { return; }
printf("Found the device we're interested in!\n");
BLEDevice::getScan()->stop();
// Hand over the device to the other task
theDevice = advertisedDevice;
}
};
void connectTask(void *pvParameters) {
uint8_t sequenceNumber = 0;
while (true) {
if (!theDevice) {
vTaskDelay(1000 / portTICK_PERIOD_MS);
continue;
}
if (!theClient) {
theClient = BLEDevice::createClient();
theClient->setConnectionParams(6, 6, 0, 42);
auto callbacks = new MyClientCallbacks();
theClient->setClientCallbacks(callbacks);
auto success = theClient->connect(theDevice);
if (!success) {
printf("Error: Could not connect to device\n");
break;
}
vTaskDelay(2000 / portTICK_PERIOD_MS);
continue;
}
if (!theChannel) {
printf("l2cap channel not initialized\n");
vTaskDelay(2000 / portTICK_PERIOD_MS);
continue;
}
if (!theChannel->isConnected()) {
printf("l2cap channel not connected\n");
vTaskDelay(2000 / portTICK_PERIOD_MS);
continue;
}
while (theChannel->isConnected()) {
/*
static auto initialDelay = true;
if (initialDelay) {
printf("Waiting gracefully 3 seconds before sending data\n");
vTaskDelay(3000 / portTICK_PERIOD_MS);
initialDelay = false;
};
*/
std::vector<uint8_t> data(5000, sequenceNumber++);
if (theChannel->write(data)) {
bytesSent += data.size();
} else {
printf("failed to send!\n");
abort();
}
}
vTaskDelay(1000 / portTICK_PERIOD_MS);
}
}
extern "C"
void app_main(void) {
printf("Starting L2CAP client example\n");
xTaskCreate(connectTask, "connectTask", 5000, NULL, 1, NULL);
BLEDevice::init("L2CAP-Client");
BLEDevice::setMTU(BLE_ATT_MTU_MAX);
auto scan = BLEDevice::getScan();
auto callbacks = new MyAdvertisedDeviceCallbacks();
scan->setScanCallbacks(callbacks);
scan->setInterval(1349);
scan->setWindow(449);
scan->setActiveScan(true);
scan->start(25 * 1000, false);
int numberOfSeconds = 0;
while (bytesSent == 0) {
vTaskDelay(10 / portTICK_PERIOD_MS);
}
while (true) {
vTaskDelay(1000 / portTICK_PERIOD_MS);
int bytesSentPerSeconds = bytesSent / ++numberOfSeconds;
printf("Bandwidth: %d b/sec = %d KB/sec\n", bytesSentPerSeconds, bytesSentPerSeconds / 1024);
}
}
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# Override some defaults so BT stack is enabled
# in this example
#
# BT config
#
CONFIG_BT_ENABLED=y
CONFIG_BTDM_CTRL_MODE_BLE_ONLY=y
CONFIG_BTDM_CTRL_MODE_BR_EDR_ONLY=n
CONFIG_BTDM_CTRL_MODE_BTDM=n
CONFIG_BT_BLUEDROID_ENABLED=n
CONFIG_BT_NIMBLE_ENABLED=y
CONFIG_BT_NIMBLE_L2CAP_COC_MAX_NUM=1
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# The following lines of boilerplate have to be in your project's
# CMakeLists in this exact order for cmake to work correctly
cmake_minimum_required(VERSION 3.5)
include($ENV{IDF_PATH}/tools/cmake/project.cmake)
set(SUPPORTED_TARGETS esp32 esp32s3 esp32c3 esp32c6)
project(L2CAP_server)
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PROJECT_NAME := L2CAP_server
include $(IDF_PATH)/make/project.mk
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set(COMPONENT_SRCS "main.cpp")
set(COMPONENT_ADD_INCLUDEDIRS ".")
register_component()
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#
# "main" pseudo-component makefile.
#
# (Uses default behaviour of compiling all source files in directory, adding 'include' to include path.)
@@ -0,0 +1,3 @@
dependencies:
local/esp-nimble-cpp:
path: ../../../../../esp-nimble-cpp/
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#include <NimBLEDevice.h>
// See the following for generating UUIDs:
// https://www.uuidgenerator.net/
#define SERVICE_UUID "dcbc7255-1e9e-49a0-a360-b0430b6c6905"
#define CHARACTERISTIC_UUID "371a55c8-f251-4ad2-90b3-c7c195b049be"
#define L2CAP_CHANNEL 150
#define L2CAP_MTU 5000
class GATTCallbacks: public BLEServerCallbacks {
public:
void onConnect(BLEServer* pServer, BLEConnInfo& info) {
/// Booster #1
pServer->setDataLen(info.getConnHandle(), 251);
/// Booster #2 (especially for Apple devices)
BLEDevice::getServer()->updateConnParams(info.getConnHandle(), 12, 12, 0, 200);
}
};
class L2CAPChannelCallbacks: public BLEL2CAPChannelCallbacks {
public:
bool connected = false;
size_t numberOfReceivedBytes;
uint8_t nextSequenceNumber;
public:
void onConnect(NimBLEL2CAPChannel* channel) {
printf("L2CAP connection established\n");
connected = true;
numberOfReceivedBytes = nextSequenceNumber = 0;
}
void onRead(NimBLEL2CAPChannel* channel, std::vector<uint8_t>& data) {
numberOfReceivedBytes += data.size();
size_t sequenceNumber = data[0];
printf("L2CAP read %d bytes w/ sequence number %d", data.size(), sequenceNumber);
if (sequenceNumber != nextSequenceNumber) {
printf("(wrong sequence number %d, expected %d)\n", sequenceNumber, nextSequenceNumber);
} else {
printf("\n");
nextSequenceNumber++;
}
}
void onDisconnect(NimBLEL2CAPChannel* channel) {
printf("L2CAP disconnected\n");
connected = false;
}
};
extern "C"
void app_main(void) {
printf("Starting L2CAP server example [%lu free] [%lu min]\n", esp_get_free_heap_size(), esp_get_minimum_free_heap_size());
BLEDevice::init("L2CAP-Server");
BLEDevice::setMTU(BLE_ATT_MTU_MAX);
auto cocServer = BLEDevice::createL2CAPServer();
auto l2capChannelCallbacks = new L2CAPChannelCallbacks();
auto channel = cocServer->createService(L2CAP_CHANNEL, L2CAP_MTU, l2capChannelCallbacks);
auto server = BLEDevice::createServer();
server->setCallbacks(new GATTCallbacks());
auto service = server->createService(SERVICE_UUID);
auto characteristic = service->createCharacteristic(CHARACTERISTIC_UUID, NIMBLE_PROPERTY::READ);
characteristic->setValue(L2CAP_CHANNEL);
service->start();
auto advertising = BLEDevice::getAdvertising();
advertising->addServiceUUID(SERVICE_UUID);
advertising->enableScanResponse(true);
BLEDevice::startAdvertising();
printf("Server waiting for connection requests [%lu free] [%lu min]\n", esp_get_free_heap_size(), esp_get_minimum_free_heap_size());
// Wait until transfer actually starts...
while (!l2capChannelCallbacks->numberOfReceivedBytes) {
vTaskDelay(10 / portTICK_PERIOD_MS);
}
printf("\n\n\n");
int numberOfSeconds = 0;
while (true) {
vTaskDelay(1000 / portTICK_PERIOD_MS);
if (!l2capChannelCallbacks->connected) { continue; }
int bps = l2capChannelCallbacks->numberOfReceivedBytes / ++numberOfSeconds;
printf("Bandwidth: %d b/sec = %d KB/sec [%lu free] [%lu min]\n", bps, bps / 1024, esp_get_free_heap_size(), esp_get_minimum_free_heap_size());
}
}
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# Override some defaults so BT stack is enabled
# in this example
#
# BT config
#
CONFIG_BT_ENABLED=y
CONFIG_BTDM_CTRL_MODE_BLE_ONLY=y
CONFIG_BTDM_CTRL_MODE_BR_EDR_ONLY=n
CONFIG_BTDM_CTRL_MODE_BTDM=n
CONFIG_BT_BLUEDROID_ENABLED=n
CONFIG_BT_NIMBLE_ENABLED=y
CONFIG_BT_NIMBLE_L2CAP_COC_MAX_NUM=1