How i write multiple float data to Arduino from Rpi as master via i2c?

问题

I read many post how Rpi receives float data via Arduino via i2c, with Rpi as master.

But i need write floats values to arduino and i don't found any example. I want to use python smbus.

Any one have a example?

Thanks a lot!

回答1:

After many tests, i can exchange multiple data between arduino as slave and Raspberry pi3 as master.

Arduino code:

#include <Wire.h>
byte data[12];
int command;

typedef struct processData{
  float temp1;
  float temp2;
  float temp3;
  float temp4;
  float vazao_quente;
  float vazao_fria;
  byte pump_speed;
  //bool  pump_status;
  byte bstatus;
  //bool heater_status;
  byte chksum;
};

typedef union I2C_Send{
  processData data;
  byte I2C_packet[sizeof(processData)];
};


I2C_Send send_info;


void parseValues(byte data[]){
  union float_tag{
    byte b[4];
    float fval;
  }ft;

  ft.b[0] =data[1];
  ft.b[1] = data[2];
  ft.b[2] = data[3];
  ft.b[3] = data[4];

  Serial.println(ft.fval);
}

void setup()
{
  Wire.begin(12);                // join i2c bus with address #4
  Wire.onReceive(receiveEvent); // register event
  Wire.onRequest(requestEvent);
  Serial.begin(9600);           // start serial for output
  setrnddata();
}

void loop()
{
  delay(100);
}

// function that executes whenever data is received from master
// this function is registered as an event, see setup()
void receiveEvent(int howMany)
{
  command = Wire.read();
  if (command==1){
    int i=0;
    while(1 <= Wire.available()) // loop through all but the last
    {
      data[i] = Wire.read(); // receive byte as a character
      i = i+1;
    }
    parseValues(data);
  }
}

void requestEvent()
{
    if(command==2){
      Wire.write(send_info.I2C_packet,sizeof(processData));
    }
}

Raspberry code:

from datetime import datetime
from datetime import timedelta
from smbus import SMBus
import struct

start_time = datetime.now()

def millis():
    dt = datetime.now()-start_time
    ms = (dt.days*24*60*60 + dt.seconds)*1000+dt.microseconds / 1000.0  
    return ms

#inicia escravo i2c
bus = SMBus(1) 
arduinoAddress = 12

#interval request
interval = 150

temperatura = 10.2
vazao = 5.3
command = 20
teste = 30

if __name__ == '__main__':
    prevmillis = millis()

    while True:
        currentmillis = millis()
        if(currentmillis - prevmillis > interval):

            #write

            bytescommand = struct.pack('=2fbb',temperatura,vazao,command,teste)
            bus.write_block_data(arduinoAddress,1,list(bytescommand))
            print(list(bytescommand))

            #request
            block = bus.read_i2c_block_data(arduinoAddress,2,27)
            output = struct.unpack('6f3b',bytes(block))
            print(output)
            print(datetime.now().strftime('%Y-%m-%d %H:%M:%S.%f')[:-3])
            prevmillis = currentmillis

I hope helps someone! Thanks!

来源：https://stackoverflow.com/questions/45774308/how-i-write-multiple-float-data-to-arduino-from-rpi-as-master-via-i2c