notes on Bluetooth between two Arduino Uno with SEEED's Grove Serial Bluetooth v3.0 module

This blog post presents a use case of setting up wireless communication between two Arduino Uno boards using Seeed's Grove Serial Bluetooth v3.0 module. The post demonstrates how to program the devices using the Arduino IDE, providing instructions for configuring the module and implementing seamless data exchange. The Grove Serial Bluetooth v3.0 module supports both Master and Slave modes, making it suitable for bidirectional data transfer in Arduino projects.

Example


Materials

- Arduino UNOs
- USB cables
- Grove Serial Bluetooth v3.0 modules
- wires

Part I 

Sketch

/**
* Bluetooth Classic Example
* Scan for devices - asynchronously, print device as soon as found
* query devices for SPP - SDP profile
* connect to first device offering a SPP connection
*
* Example python server:
* source: https://gist.github.com/ukBaz/217875c83c2535d22a16ba38fc8f2a91
*
* Tested with Raspberry Pi onboard Wifi/BT, USB BT 4.0 dongles, USB BT 1.1 dongles,
* 202202: does NOT work with USB BT 2.0 dongles when esp32 arduino lib is compiled with SSP support!
* see https://github.com/espressif/esp-idf/issues/8394
*
* use ESP_SPP_SEC_ENCRYPT|ESP_SPP_SEC_AUTHENTICATE in connect() if remote side requests 'RequireAuthentication': dbus.Boolean(True),
* use ESP_SPP_SEC_NONE or ESP_SPP_SEC_ENCRYPT|ESP_SPP_SEC_AUTHENTICATE in connect() if remote side has Authentication: False
*/

#include <map>
#include <BluetoothSerial.h>

#if !defined(CONFIG_BT_ENABLED) || !defined(CONFIG_BLUEDROID_ENABLED)
#error Bluetooth is not enabled! Please run `make menuconfig` to and enable it
#endif

#if !defined(CONFIG_BT_SPP_ENABLED)
#error Serial Bluetooth not available or not enabled. It is only available for the ESP32 chip.
#endif

BluetoothSerial SerialBT;

#define BT_DISCOVER_TIME 10000
esp_spp_sec_t sec_mask = ESP_SPP_SEC_NONE; // or ESP_SPP_SEC_ENCRYPT|ESP_SPP_SEC_AUTHENTICATE to request pincode confirmation
esp_spp_role_t role = ESP_SPP_ROLE_SLAVE; // or ESP_SPP_ROLE_MASTER

// std::map<BTAddress, BTAdvertisedDeviceSet> btDeviceList;

void setup() {
Serial.begin(115200);
if (!SerialBT.begin("ESP32test", true)) {
Serial.println("========== serialBT failed!");
abort();
}
// SerialBT.setPin("1234"); // doesn't seem to change anything
// SerialBT.enableSSP(); // doesn't seem to change anything

Serial.println("Starting discoverAsync...");
BTScanResults *btDeviceList = SerialBT.getScanResults(); // maybe accessing from different threads!
if (SerialBT.discoverAsync([](BTAdvertisedDevice *pDevice) {
// BTAdvertisedDeviceSet*set = reinterpret_cast<BTAdvertisedDeviceSet*>(pDevice);
// btDeviceList[pDevice->getAddress()] = * set;
Serial.printf(">>>>>>>>>>>Found a new device asynchronously: %s\n", pDevice->toString().c_str());
})) {
delay(BT_DISCOVER_TIME);
Serial.print("Stopping discoverAsync... ");
SerialBT.discoverAsyncStop();
Serial.println("discoverAsync stopped");
delay(5000);
if (btDeviceList->getCount() > 0) {
BTAddress addr;
int channel = 0;
Serial.println("Found devices:");
for (int i = 0; i < btDeviceList->getCount(); i++) {
BTAdvertisedDevice *device = btDeviceList->getDevice(i);
Serial.printf(" ----- %s %s %d\n", device->getAddress().toString().c_str(), device->getName().c_str(), device->getRSSI());
std::map<int, std::string> channels = SerialBT.getChannels(device->getAddress());
Serial.printf("scanned for services, found %d\n", channels.size());
for (auto const &entry : channels) {
Serial.printf(" channel %d (%s)\n", entry.first, entry.second.c_str());
}
if (channels.size() > 0) {
addr = device->getAddress();
channel = channels.begin()->first;
}
}
if (addr) {
Serial.printf("connecting to %s - %d\n", addr.toString().c_str(), channel);
SerialBT.connect(addr, channel, sec_mask, role);
}
} else {
Serial.println("Didn't find any devices");
}
} else {
Serial.println("Error on discoverAsync f.e. not working after a \"connect\"");
}
}

String sendData = "Hi from esp32!\n";

void loop() {
if (!SerialBT.isClosed() && SerialBT.connected()) {
if (SerialBT.write((const uint8_t *)sendData.c_str(), sendData.length()) != sendData.length()) {
Serial.println("tx: error");
} else {
Serial.printf("tx: %s", sendData.c_str());
}
if (SerialBT.available()) {
Serial.print("rx: ");
while (SerialBT.available()) {
int c = SerialBT.read();
if (c >= 0) {
Serial.print((char)c);
}
}
Serial.println();
}
} else {
Serial.println("not connected");
}
delay(1000);
}

Part II 

Sketch

#include <SoftwareSerial.h> //Software Serial Port

#define RxD 7
#define TxD 6


#define DEBUG_ENABLED 1

SoftwareSerial blueToothSerial(RxD,TxD);

void setup()
{
Serial.begin(9600);
pinMode(RxD, INPUT);
pinMode(TxD, OUTPUT);
setupBlueToothConnection();
}

void loop()
{
char recvChar;
if(blueToothSerial.available())
{//check if there's any data sent from the remote bluetooth shield
recvChar = blueToothSerial.read();
Serial.print(recvChar);
}
if(Serial.available())
{//Keep reading from Arduino Serial Monitor and send it out
blueToothSerial.write(Serial.read());
}
}

/***************************************************************************
* Function Name: setupBlueToothConnection
* Description: initilizing bluetooth connction
* Parameters:
* Return:
***************************************************************************/
void setupBlueToothConnection()
{
blueToothSerial.begin(9600);
blueToothSerial.print("AT");
delay(400);
blueToothSerial.print("AT+DEFAULT"); // Restore all setup value to factory setup
delay(2000);
blueToothSerial.print("AT+NAMESeeedBTTarget"); // set the bluetooth name as "SeeedBTTarget"
delay(400);
blueToothSerial.print("AT+PIN0000"); // set the pair code to connect
delay(400);
blueToothSerial.print("AT+AUTH0"); //
delay(400);
blueToothSerial.flush();
}

References

[1] https://wiki.seeedstudio.com/Grove-Serial_Bluetooth_v3.0/

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