esp-idf-vcp2ble

VCP(Virtual COM Port) to Bluetooth bridge for ESP-IDF.

ESP-IDF supports VCP hosts.
VCP hosts can communicate with VCP devices using the USB port.
Representative VCP devices include Arduino Uno and Arduino Mega, which have a UART-USB conversion chip.
I based it on this.

This project uses the following components.
Other UART-USB converter chips are not supported.

• https://components.espressif.com/components/espressif/usb_host_ch34x_vcp
• https://components.espressif.com/components/espressif/usb_host_cp210x_vcp
• https://components.espressif.com/components/espressif/usb_host_ftdi_vcp

BLE host stack

ESP-IDF can use either the ESP-Bluedroid host stack or the ESP-NimBLE host stack.
The differences between the two are detailed here.
This project uses the ESP-NimBLE host stack.

Software requirements

ESP-IDF V5.0 or later.
ESP-IDF V4.4 release branch reached EOL in July 2024.

Hardtware requirements

ESP32-S3

This project only works with ESP32S3.
The ESP32S3 has both USB and BLE capabilities.
The ESP32S2 also has USB capabilities, but does not have BLE capabilities.

USB Type-A Femail connector

USB connectors are available from AliExpress or eBay.
I used it by incorporating it into a Universal PCB.

We can buy this breakout on Ebay or AliExpress.

Installation

git clone https://github.com/nopnop2002/esp-idf-vcp2ble
cd esp-idf-vcp2ble
idf.py set-target esp32s3
idf.py menuconfig
idf.py flash

Configuration

VCP communication stop bits. 0: 1 stopbit, 1: 1.5 stopbits, 2: 2 stopbits
VCP communication parity. 0: None, 1: Odd, 2: Even, 3: Mark, 4: Space

Write this sketch on Arduino Uno.

You can use any AtMega microcontroller that has a USB port.

unsigned long lastMillis = 0;

void setup() {
  Serial.begin(115200);
}

void loop() {
  while (Serial.available()) {
    String command = Serial.readStringUntil('\n');
    Serial.println(command);
  }

  if(lastMillis + 1000 <= millis()){
    Serial.print("Hello World ");
    Serial.println(millis());
    lastMillis += 1000;
  }

  delay(1);
}

Strings from Arduino to ESP32 are terminated with CR(0x0d)+LF(0x0a).

I (1482) VCP: Receiving data through CdcAcmDevice
I (1482) VCP: 0x3fcba0a8   48 65 6c 6c 6f 20 57 6f  72 6c 64 20 36 36 30 30  |Hello World 6600|
I (1492) VCP: 0x3fcba0b8   30 0d 0a                                          |0..|

The Arduino sketch inputs data with LF as the terminator.
So strings from the ESP32 to the Arduino must be terminated with LF (0x0a).
If the string output from the ESP32 to the Arduino is not terminated with LF (0x0a), the Arduino sketch will complete the input with a timeout.
The default input timeout for Arduino sketches is 1000 milliseconds.
The ESP32 SPP driver always sends data to the application with CR+LF as the termination character.
This project changes the termination character from CR+LF to LF and sends the data to Arduino.
The Arduino sketch will echo back the string it reads.

I (78212) VCP: Sending data through CdcAcmDevice
I (78222) VCP: 0x3fcb7930   61 62 63 64 65 66 67 0a                           |abcdefg.|
I (78232) VCP: Receiving data through CdcAcmDevice
I (78232) VCP: 0x3fcba0a8   61 62 63 64 65 66 67 0d  0a                       |abcdefg..|

Wireing

Arduino Uno connects via USB connector.
The USB port on the ESP32S3 development board does not function as a USB-HOST.

+---------+  +-------------+  +-----------+
|ESP BOARD|==|USB CONNECTOR|==|Arduino Uno|
+---------+  +-------------+  +-----------+

ESP BOARD          USB CONNECTOR (type A)
                         +--+
5V        -------------> | || VCC
[GPIO19]  -------------> | || D-
[GPIO20]  -------------> | || D+
GND       -------------> | || GND
                         +--+

Android Application

I used this app.

• pair with ESP_NIMBLE_SERVER

• Launch the app and select device
  Menu->Devices->Bluetooth LE

• Long press the device and select the Edit menu
  

• Select Custom and specify UUID
  

• Connect to device
  You can communicate with UNO via BLE.
  

• Concurrent connection
  Unlike ESP-Bluedroid host stack, ESP-NimBLE host stack allows concurrent connections.
  The maximum number of simultaneous connections is specified here.
  
  

iOS Application

This might work, but I don't have iOS so I don't know.