我通过蓝牙向 arduino nano ble 33 发送了一个值，并接收到了树莓派的值。 如何将此值转换为数字？

Question

Currently, I am working on the part that transmits data through Bluetooth using Arduino Nano 33 BLE.

The part of sending the value from Arduino to Raspberry Pi was completed using Bluetooth during the work, but the output value received using Python from the Raspberry Pi was output as {' rsp ': ['wr']} instead of a number.

I am trying to proceed through this method while browsing various documents. How can I get the output value as a numeric value rather than an output value like {' rsp ': ['wr']} ?

If the value cannot be received as a number, should it be transformed into a Python code written in socket??

First, it is an example related to the Arduino battery, which is a commonly used code, and I tried to transform it in the way I want based on that code.

In that part, I changed the !Serial part to the Serial part so that it works even when not connected to the computer port.

In that case, I don't think there's a problem because it works just as well as I thought.

Arduino Sample Code

#include <ArduinoBLE.h>
BLEService ledService("19B10000-E8F2-537E-4F6C-D104768A1214"); // BLE LED Service
// BLE LED Switch Characteristic - custom 128-bit UUID, read and writable by central
BLEByteCharacteristic switchCharacteristic("19B10001-E8F2-537E-4F6C-D104768A1214", BLERead | BLEWrite);

const int ledPin = LED_BUILTIN; // pin to use for the LED

void setup() {
  Serial.begin(9600);
  while (!Serial);
  // set LED pin to output mode
  pinMode(ledPin, OUTPUT);
  // begin initialization
  if (!BLE.begin()) {
    Serial.println("starting BLE failed!");
    while (1);
  }
  // set advertised local name and service UUID:
  BLE.setLocalName("LED");
  BLE.setAdvertisedService(ledService);
  // add the characteristic to the service
  ledService.addCharacteristic(switchCharacteristic);
  // add service
  BLE.addService(ledService);
  // set the initial value for the characeristic:
  switchCharacteristic.writeValue(0);
  // start advertising
  BLE.advertise();
  Serial.println("BLE LED Peripheral");
}

void loop() {
  // listen for BLE peripherals to connect:
  BLEDevice central = BLE.central();
  // if a central is connected to peripheral:
  if (central) {
    Serial.print("Connected to central: ");
    //prints the centrals MAC address:
    Serial.println(central.address());
    // while the central is still connected to peripheral:
    while (central.connected()) {
      // if the remote device wrote to the characteristic,
      // use the value to control the LED:
      if (switchCharacteristic.written()) {
        if (switchCharacteristic.value()) { // any value other than 0
          Serial.println("LED on");
          digitalWrite(ledPin, HIGH); // will turn the LED on
        } else { // a 0 value
          Serial.println(F("LED off"));
          digitalWrite(ledPin, LOW); // will turn the LED off
        }
      }
    }
    // when the central disconnects, print it out:
    Serial.print(F("Disconnected from central: "));
    Serial.println(central.address());
  }
}

Here is the raspberry pi code

import bluepy.btle as btle

p1 = btle.Peripheral("2D:20:48:59:8F:B4")
services1=p1.getServices()
s1 = p1.getServiceByUUID(list(services1)[2].uuid)
c1 = s1.getCharacteristics()[0]
a1=c1.write(bytes("0001".encode()))
p1.disconnect()

When the code is executed, the result is as follows:

{'rsp': ['wr']}

In the above code, I want to output a numeric value from the result. How do I modify the code in Python or Arduino on Raspberry Pi so that the output value in Python on Raspberry Pi comes out as a number?

Answer 1

It looks like you want to write either a zero or a one to the Arduino from the Raspberry Pi. You are using bytes("0001".encode()) but this will use the ASCII values for the characters. For example:

>>> list(bytes("0001".encode()))
[48, 48, 48, 49]
>>> list(bytes("0000".encode()))
[48, 48, 48, 48]

There are a couple of ways to create bytes of a numeric value:

>>> list(struct.pack('b', 0))
[0]
>>> list(struct.pack('b', 1))
[1]
>>> list(int(0).to_bytes(1, byteorder='little'))
[0]
>>> list(int(1).to_bytes(1, byteorder='little'))
[1]

Note: I've wrapped all of the commands in list() just to show the results in common formatting and is unnecessary for your code

I would also recommend being more specific about the services and characteristics you are geting by specifying the UUIDs. For example:

import bluepy.btle as btle
from bluepy.btle import UUID

ledService = UUID("19B10000-E8F2-537E-4F6C-D104768A1214")
switchCharacteristic = UUID("19B10001-E8F2-537E-4F6C-D104768A1214")


p1 = btle.Peripheral("2D:20:48:59:8F:B4")
services1 = p1.getServices()
s1 = p1.getServiceByUUID(ledService)
c1 = s1.getCharacteristics(switchCharacteristic)[0]
a1 = c1.write(struct.pack('b', 1))
p1.disconnect()