BLE_SimpleChat example for Readbear BLE NANO adapted to send potentiometer.

BLE_Potentiometer_Chat.ino

#include <BLE_API.h>

#define DEVICE_NAME          "PotentiometerToChat"
#define TXRX_BUF_LEN         20

#define DEVICE_ID            0xFF

BLE                          ble;


const int SOFT_POT_PIN = A3; // Pin connected to softpot wiper

const int GRAPH_LENGTH = 40; // Length of line graph


// The uuid of service and characteristics
static const uint8_t service1_uuid[]         = {0x71, 0x3D, 0, 0, 0x50, 0x3E, 0x4C, 0x75, 0xBA, 0x94, 0x31, 0x48, 0xF1, 0x8D, 0x94, 0x1E};
static const uint8_t service1_chars1_uuid[]  = {0x71, 0x3D, 0, 3, 0x50, 0x3E, 0x4C, 0x75, 0xBA, 0x94, 0x31, 0x48, 0xF1, 0x8D, 0x94, 0x1E};
static const uint8_t service1_chars2_uuid[]  = {0x71, 0x3D, 0, 2, 0x50, 0x3E, 0x4C, 0x75, 0xBA, 0x94, 0x31, 0x48, 0xF1, 0x8D, 0x94, 0x1E};
static const uint8_t uart_base_uuid_rev[]    = {0x1E, 0x94, 0x8D, 0xF1, 0x48, 0x31, 0x94, 0xBA, 0x75, 0x4C, 0x3E, 0x50, 0, 0, 0x3D, 0x71};

uint8_t chars1_value[TXRX_BUF_LEN] = {0};
uint8_t chars2_value[TXRX_BUF_LEN] = {0};

// Create characteristic and service
GattCharacteristic  characteristic1(service1_chars1_uuid, chars1_value, 1, TXRX_BUF_LEN, GattCharacteristic::BLE_GATT_CHAR_PROPERTIES_WRITE | GattCharacteristic::BLE_GATT_CHAR_PROPERTIES_WRITE_WITHOUT_RESPONSE );
GattCharacteristic  characteristic2(service1_chars2_uuid, chars2_value, 1, TXRX_BUF_LEN, GattCharacteristic::BLE_GATT_CHAR_PROPERTIES_NOTIFY | GattCharacteristic::BLE_GATT_CHAR_PROPERTIES_READ);
GattCharacteristic *uartChars[] = {&characteristic1, &characteristic2};
GattService         uartService(service1_uuid, uartChars, sizeof(uartChars) / sizeof(GattCharacteristic *));


void disconnectionCallBack(const Gap::DisconnectionCallbackParams_t *params) {
  ble.startAdvertising();
}

void gattServerWriteCallBack(const GattWriteCallbackParams *Handler) {
  uint8_t buf[TXRX_BUF_LEN];
  uint16_t bytesRead, index;

  Serial.println("Write Handle : ");
  if (Handler->handle == characteristic1.getValueAttribute().getHandle()) {
    ble.readCharacteristicValue(characteristic1.getValueAttribute().getHandle(), buf, &bytesRead);
    for(index=0; index<bytesRead; index++)
    {
        Serial.print(buf[index], HEX);
    }
//    write_handle();
  }
}


void setup() {
  // put your setup code here, to run once
  Serial.begin(9600);
  Serial.println("Start ");

  // ticker_task1.attach(sendMessage, 2);

  
  ble.init();
  ble.onDisconnection(disconnectionCallBack);
  ble.onDataWritten(gattServerWriteCallBack);
  // setup adv_data and srp_data
  ble.accumulateAdvertisingPayload(GapAdvertisingData::BREDR_NOT_SUPPORTED);
  ble.accumulateAdvertisingPayload(GapAdvertisingData::SHORTENED_LOCAL_NAME,
                                   (const uint8_t *)DEVICE_NAME, sizeof(DEVICE_NAME) - 1);
  ble.accumulateAdvertisingPayload(GapAdvertisingData::COMPLETE_LIST_128BIT_SERVICE_IDS,
                                   (const uint8_t *)uart_base_uuid_rev, sizeof(uart_base_uuid_rev));
  // set adv_type
  ble.setAdvertisingType(GapAdvertisingParams::ADV_CONNECTABLE_UNDIRECTED);
  // add service
  ble.addService(uartService);
  // set device name
  ble.setDeviceName((const uint8_t *)DEVICE_NAME);
  // set tx power,valid values are -40, -20, -16, -12, -8, -4, 0, 4
  ble.setTxPower(4);
  // set adv_interval, 100ms in multiples of 0.625ms.
  ble.setAdvertisingInterval(160);
  // set adv_timeout, in seconds
  ble.setAdvertisingTimeout(0);
  
  ble.startAdvertising();
  Serial.println("start advertising ");
}



void loop() {
  // put your main code here, to run repeatedly:
  ble.waitForEvent();

   // Read in the soft pot's ADC value
  int softPotADC = analogRead(SOFT_POT_PIN);
  // Map the 0-1023 value to 0-40. On testing the actual values are between 350 and 700
  int softPotPosition = map(softPotADC, 350, 700, 0, GRAPH_LENGTH);
  if (softPotPosition>0)
    uint8_t buf[2] = {softPotPosition, (softPotPosition >> 8)}; ble.updateCharacteristicValue(characteristic2.getValueAttribute().getHandle(), buf, sizeof(buf) - 1 );

  delay(500);
}

Some Tips with BLE Nano.md

BLE Nano Tips

• I found it hard to use interrupts
• I use Arduino UNO to test things before putting the code to BLE Nano. This is because of the painful slow development with Nano, where compiling takes ages and then you have to remove it from USB to put it on Breadboard and back.
• I was trying Evothings. Although buggy, it really helps with the debugging flow as it shows logs on javascript console.