Send/Receive Floats

[smithdsl]

Hello Guys.

I have two Flutter broads, one connected to a 10DOF IMU sending data (local Flutter) and the other receiving (remote Flutter). I'm trying to send float numbers from a 10DOF chip to a remote monitor. So far I can read the sensors and print the data on the "local Flutter" but receiving the data is not working as i thought. Each byte comes over as a decimal not a hexadecimal number. Can anyone help me in converting this into a hexadecimal number and then to a floating point number. My hope is to send data from the IMU to the remote host to react to conditions (if temp is x do y).

My current code is based on the remote control car example:

As a test I'm trying to send a float of -86.78 as 4 bytes that equal C2 AD 8F 5C. The receiver gets each byte as a decimal value 192 173 143 92. Tried to put this into a union to recreate the float, but it doesn't equal the original.

Float = -86.78
Hex = C2 AD 8F 5C
Binary = 11000010 10101101 10001111 01011100
decimal = 3266154332

Transmitter:

    /*
This example code for Flutter is
Copyright 2015, Taylor Alexander and Flutter Wireless, Inc.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

#include "Flutter.h"


boolean _running = false;
Flutter flutter;




void setup()
{
	Serial.begin(115200);
	flutter.band = NORTH_AMERICA;
	flutter.setNetworkName("Home network");
	//pinMode(6,OUTPUT);
	//pinMode(7,OUTPUT);
	Serial.println("Initializing...");

	if (flutter.init() == true)
	{
		Serial.println("Init success.");
		flutter.ledLightShow();
		delay(500);
		//analogWrite(LED_R, 128);
	}
	else
	{
		flutter.setLED(RED);
		Serial.println("Init failed.");

		while (true);
	}

	//flutter.setAddress(1);
	flutter.setAddress(1);
	flutter.connect(1); //form a network with this and one other device
	
}



void loop()
{
	while (flutter.getState() != NORMAL_OPERATION) //if we aren't synchronized with another radio, just loop and blink lights.
	{
		flutter.setLED(RED);
		delay(200);
		flutter.setLED(BLUE);
		delay(200);
	}


        flutter.setLED(YELLOW);
        delay(500);
//	float r = -180.72;
//        float p = 360.32;
//        float h = 234.06;



	byte mydata[4] = {0x64, 0x34, 0x56, 0x45,};
	//send a byte over the radio
	flutter.sendData(mydata, 4, 2); //legth is 3, 2 is car's address
	//make our LED do nice colors

	flutter.setLED(PURPLE);



	delay(2000); //spend some time smelling the roses
}


void button1()
{
	interrupts();
	int val = digitalRead(BUTTON1); //top button

	if (val == HIGH)
	{
		// _button1=255;
	}
	else
	{
		//  _button1=0;
	}

// buttonsChanged=true;
}

void button2()
{
	interrupts();
	int val = digitalRead(BUTTON2);
#ifdef FLUTTER_R2

	if (val == HIGH)
#else
	if (val == LOW)
#endif
	{
		//_button2=255;
	}
	else
	{
		//_button2=0;
	}

// buttonsChanged=true;
}

void systemReset()
{
	flutter.setLED(0, 0, 255);
	delayMicroseconds(16000);
	delayMicroseconds(16000);
	flutter.setLED(0, 0, 0);
	delayMicroseconds(16000);
	delayMicroseconds(16000);
	flutter.setLED(0, 255, 0);
	delayMicroseconds(16000);
	delayMicroseconds(16000);
	flutter.setLED(0, 0, 0);
	delayMicroseconds(16000);
	delayMicroseconds(16000);
	flutter.setLED(255, 0, 0);
	delayMicroseconds(16000);
	delayMicroseconds(16000);
	flutter.setLED(0, 0, 0);
	initiateReset(1);
	tickReset();
}



void radioInterrupt()
{
	flutter.interrupt();
}
void softInt()
{
	flutter.processSoftInt();
}

extern boolean tickInterrupt()
{
	if (!flutter.initialized)
	{
		return true;
	}

	return flutter.tickInt();
}

Receiver:

/*
This example code for Flutter is
Copyright 2015, Taylor Alexander and Flutter Wireless, Inc.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

#include "Flutter.h"

#define bitRead(value, bit) (((value) >> (bit)) & 0x01)

byte myData = 0;
boolean _running = false;
Flutter flutter;

float tempF = 0;



void setup()
{
	Serial.begin(57600);
	flutter.band = NORTH_AMERICA;
	flutter.setNetworkName("Home network");

	Serial.println("Initializing...");

	if (flutter.init() == true)
	{
		Serial.println("Init success.");
		flutter.ledLightShow();
		delay(500);
		//analogWrite(LED_R, 128);
	}
	else
	{
		flutter.setLED(RED);
		Serial.println("Init failed.");

		while (true);
	}

	//flutter.setAddress(1);
	flutter.setAddress(2);
	flutter.connect(1); //form a network with this and one other device
}



void loop()
{
		while(flutter.getState()!=NORMAL_OPERATION) //if we aren't synchronized with another radio, just loop and blink lights.
		{
			flutter.setLED(RED);
			delay(200);
			flutter.setLED(BLUE);
			delay(200);
		}
	

	//read the radio to see if there is data available
	if (flutter.dataAvailable() > 0)
	{
                flutter.setLED(0xff, 0xff, 0xff);
  		int packetSize = flutter.nextPacketLength();
		byte array[packetSize];
              
               // union u_tag{
               //  float f;
               //  byte b[4];
               // } num;

                             
		//flutter.readBytes(array, packetSize);
		//Serial.print("PacketSize");
		//Serial.println(packetSize);

                               
		//num.b[0] = array[5];
                //num.b[1] = array[6];
                //num.b[2] = array[7];
                //num.b[3] = array[8];
                
                //long speedLong = 0;
                //for(int i = 5; i < 9; i++)
           //      {
           //         Serial.print(array[i]); // prints the byte in hex
           //          speedLong = (speedLong << 8) | array[i];
           //          float tempF = array[i];
           //      }
                Serial.print("--TRYING"); // linefeed
                //int fu = array[5] & 0xff | ((array[6] & 0xff) << 8) | ((array[7]  & 0xff) << 16) | ((array[8]  & 0xff) << 24);
 
          //      Serial.println(*(float *) &fu);
                
                
               // Serial.print("SYS00 - ");
	       // Serial.println(tempF);
               // Serial.print("SYS01 - ");
		//Serial.println(array[1]);
               // Serial.print("SYS02 - ");
		//Serial.println(array[2]);
               // Serial.print("SYS03 - ");
		//Serial.println(array[3]);
               // Serial.print("SYS04 - ");
		//Serial.println(array[4], HEX);
                Serial.print("DATA05 - ");
		Serial.println(array[5], HEX);
                Serial.print("DATA06 - ");
		Serial.println(array[6], HEX);
                Serial.print("DATA07 - ");
		Serial.println(array[7], HEX);
                Serial.print("DATA08 - ");
		Serial.println(array[8], HEX);
                Serial.print("HEX09 - ");
		Serial.println(array[9]);

                delay(20);
                /*
                Serial.print("trying - ");
		Serial.println(float(num.f));
                Serial.print("byte - ");
		Serial.println(num.b[0]);
                Serial.print("byte - ");
		Serial.println(num.b[1]);
                Serial.print("byte - ");
		Serial.println(num.b[2]);
                Serial.print("byte - ");
		Serial.println(num.b[3]);
                */
                
                

                    for (int i = 0; i < 8; i++) //(uint8_t i = 0; i < 8; i++)
                    
                   ubitRead( array[5], i)
                
                Serial.print("bit- ");
		Serial.println(bitst);
                Serial.print("bit- ");
		Serial.println(array[6]);
                Serial.print("bit- ");
		Serial.println(array[7]);
                Serial.print("bit-");
		Serial.println(array[8]);

                  

		delay(200);

	        flutter.setLED(0x8b, 0x1c, 0x62);
		//delay(10);
		flutter.nextPacket();
	}

	//delay(50); //spend some time smelling the roses
}


void button1()
{
	interrupts();
	int val = digitalRead(BUTTON1); //top button

	if (val == HIGH)
	{
		// _button1=255;
	}
	else
	{
		//  _button1=0;
	}

// buttonsChanged=true;
}

void button2()
{
	interrupts();
	int val = digitalRead(BUTTON2);
#ifdef FLUTTER_R2

	if (val == HIGH)
#else
	if (val == LOW)
#endif
	{
		//_button2=255;
	}
	else
	{
		//_button2=0;
	}

// buttonsChanged=true;
}

void systemReset()
{
	flutter.setLED(0, 0, 255);
	delayMicroseconds(16000);
	delayMicroseconds(16000);
	flutter.setLED(0, 0, 0);
	delayMicroseconds(16000);
	delayMicroseconds(16000);
	flutter.setLED(0, 255, 0);
	delayMicroseconds(16000);
	delayMicroseconds(16000);
	flutter.setLED(0, 0, 0);
	delayMicroseconds(16000);
	delayMicroseconds(16000);
	flutter.setLED(255, 0, 0);
	delayMicroseconds(16000);
	delayMicroseconds(16000);
	flutter.setLED(0, 0, 0);
	initiateReset(1);
	tickReset();
}



void radioInterrupt()
{
	flutter.interrupt();
}
void softInt()
{
	flutter.processSoftInt();
}

extern boolean tickInterrupt()
{
	if (!flutter.initialized)
	{
		return true;
	}

	return flutter.tickInt();
}

Thanks for your help.

[Jarrod_s]

Hi smithdsl,
when working with floats I try to get them back into INTs as quickly as possible. It will save you a lot of headaches later and overhead. Figure out the level of precision you want (.1 or .01, etc) then multiple the float by 10 or 100 and save it in an int. This is also very helpfully if you end up doing bit packing later.

If you really want to keep floats then I recommend using a library like tinypacks that will maintain structure for you. and save a little bit of space in your messages.

Best of luck.
- Jarrod

[andrewsc4]

I am not sure that I understand the question. The processor, etc, only deals in binary. Hex C2 AD 8F 5C and decimal 3266154332 are the same number. If you have a hex byte AD and a decimal byte 173, they have the same representation in binary - byte "10101101". Decimal vs hex is just a visualization of the number. Is the difference that you see in what you output, because that would just indicate different formatting.

[smithdsl]

Thanks for the reply I'll try this and see what i get.

[smithdsl]

andrewsc4,

You got some of it, but my problem is on the receiver side. The receiver takes the data off the wire (air) and puts it in the decimal representation of the hex number were I can't send it to a "union" or array to convert the 4 bytes back to one floating point number.

Thanks.

[andrewsc4]

What is the actual data that you are receiving? It must not be the decimal data that you list above. I note that in the remote car example, the joystick sends 3 bytes of data, and the remote car takes bytes 6 and 7, so there may be other data that you receive beyond just the bytes that you think that you sent. If you sent a different float number, how does what ends up in your union change?

[smithdsl]

Andrewsc4,

If you look at the receiving code I snipped from above, I'm pulling packet 5,6,7,8 because 1,2,3,4 are network related, See LINK HERE for more info on the first four packets.

            // Serial.print("SYS00 - ");
       // Serial.println(tempF);
           // Serial.print("SYS01 - ");
	//Serial.println(array[1]);
           // Serial.print("SYS02 - ");
	//Serial.println(array[2]);
           // Serial.print("SYS03 - ");
	//Serial.println(array[3]);
           // Serial.print("SYS04 - ");
	//Serial.println(array[4], HEX);
            Serial.print("DATA05 - ");
	Serial.println(array[5], HEX);
            Serial.print("DATA06 - ");
	Serial.println(array[6], HEX);
            Serial.print("DATA07 - ");
	Serial.println(array[7], HEX);
            Serial.print("DATA08 - ");
	Serial.println(array[8], HEX);
            Serial.print("HEX09 - ");
	Serial.println(array[9]);

When I print the values from the array they come out to be decimal numbers. Now if add the key word "HEX" to the "Serial.print" it will show the HEX values on the term monitor, but the value is still a decimal if I do something like :

  union u_tag{
            float f;
            byte b[4];
            } num;

                         
                           
            num.b[0] = array[5];
            num.b[1] = array[6];
            num.b[2] = array[7];
            num.b[3] = array[8];

You can run this code on your Flutter and test to see if I'm doing something wrong ( which i kind of hoping I am). I removed the IMU code so this should run on you flutter too.
Thank again.

[jeffcraighead]

I think the basic problem is that you are never putting them back into a float. You are setting the byte array field of the Union which means it will be interpreted as a byte array. You need to set the float field using bit shift operators. Something like:

num.f = (array[5]<<24) & (array[6] <<16) & (array[7]<<8) & array[8].

You may need to cast the array values to int of float before shifting so the compiler knows to use a full 32 bits, otherwise you could end up with the wrong numbers being combined.

[smithdsl]

Jeffcraighead,

When I tried the union , result of "num.f" is 19417314392 and the "serial.print" sends "ovf" or stack overflow. This is because array[6] = 192 (0xc2), array[6] = 173 (0xad), array[7] = 143 (0x8f), array[8] = 92 (0x5c), so when put in the union they do not equal the float or decimal numbers we started with.

Thanks.

[andrewsc4]

I don't think that they should require being put back in a float via shifting (at least not theoretically). The whole point of the union is that the two datatypes reference the same memory. The 4 bytes of the float should map on to the 4 bytes of the byte array. The most likely problem is that the way that the data is being put into the byte array does not correspond to the alignment of the float, but I don't see where it is wrong. Using bit shift operators, with appropriate casts, might alleviate that. One approach would be to use a union on the sending side, as well, to insure that the original float is taken apart exactly like it will be reassembled on the other end.

[jeffcraighead]

Ok, that makes sense regarding accessing the union, in that the data type returned might be determined by which part of the union you use to access (read) it. However to be sure, you could he could try and put the data directly into a float with the shift ops and bypass the union. Also, take a look at http://www.h-schmidt.net/FloatConverter/IEEE754.html I think based on playing with that your endianness is wrong. That is, you're putting the bytes in backwards for a float. You may need to have 0x5c8fadc2 in your array instead.