Title: **dtostrf**

Post by:**ccomparey** on **Jan 03, 2019, 02:36 pm**

Post by:

Hello,

I am trying to use BLE to transfer orientation from a BNO055 sensor data to an app on a tablet. My orientation data from the sensor has double data type but for programming of the app it is much easier to receive the 4 components (w,x,y,z) as a string. At first I thought this would be easy using the dtostrf() function, however, now I am realizing that is only part avr library and will not work for my mkr wifi 1010. has anyone made or found a simple function to convert doubles to strings with this board?

Worded differently: I have 4 double variables and I want to convert them to a string with commas seperating each variable.

What I have

double w = 0.12

double x = -3.45

double y = 6.78

double z = -9.10

and I want to convert this to a string "0.12,-3.45,6.78,-9.10"

I have done some looking around the forum without much luck, if you know a simple solution or where i can find one it would be greatly appreciated.

Thanks,

Chris

I am trying to use BLE to transfer orientation from a BNO055 sensor data to an app on a tablet. My orientation data from the sensor has double data type but for programming of the app it is much easier to receive the 4 components (w,x,y,z) as a string. At first I thought this would be easy using the dtostrf() function, however, now I am realizing that is only part avr library and will not work for my mkr wifi 1010. has anyone made or found a simple function to convert doubles to strings with this board?

Worded differently: I have 4 double variables and I want to convert them to a string with commas seperating each variable.

What I have

double w = 0.12

double x = -3.45

double y = 6.78

double z = -9.10

and I want to convert this to a string "0.12,-3.45,6.78,-9.10"

I have done some looking around the forum without much luck, if you know a simple solution or where i can find one it would be greatly appreciated.

Thanks,

Chris

Title: **Re: dtostrf**

Post by:**ccomparey** on **Jan 04, 2019, 12:04 pm**

Post by:

If anyone else is interested in this after about 5 more hours of digging i found this thread (https://forum.arduino.cc/index.php?topic=329949.45) which at the end gives the following dtostrf function which seems to work so far.

Code: [Select]

char * dtostrf(double number, signed char width, unsigned char prec, char *s) {

if (isnan(number)) {

strcpy(s, "nan");

return s;

}

if (isinf(number)) {

strcpy(s, "inf");

return s;

}

char* out = s;

int fillme = width; // how many cells to fill for the integer part

if (prec > 0) {

fillme -= (prec+1);

}

// Handle negative numbers

if (number < 0.0) {

*out++ = '-';

fillme--;

number = -number;

}

// Round correctly so that print(1.999, 2) prints as "2.00"

// I optimized out most of the divisions

double rounding = 2.0;

for (uint8_t i = 0; i < prec; ++i)

rounding *= 10.0;

rounding = 1.0 / rounding;

number += rounding;

// Figure out how big our number really is

double tenpow = 1.0;

int digitcount = 1;

while (number >= 10.0 * tenpow) {

tenpow *= 10.0;

digitcount++;

}

number /= tenpow;

fillme -= digitcount;

// Pad unused cells with spaces

while (fillme-- > 0) {

*out++ = ' ';

}

// Print the digits, and if necessary, the decimal point

digitcount += prec;

int8_t digit = 0;

while (digitcount-- > 0) {

digit = (int8_t)number;

if (digit > 9) digit = 9; // insurance

*out++ = (char)('0' | digit);

if ((digitcount == prec) && (prec > 0)) {

*out++ = '.';

}

number -= digit;

number *= 10.0;

}

// make sure the string is terminated

*out = 0;

return s;

}

Title: **Re: dtostrf**

Post by:**pmalasp** on **May 08, 2019, 09:55 pm**

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dtostrf does not seem extremely popular, so I had my troubles and started to write my own, just in case someone else need it:

https://github.com/pmalasp/dtostrf

https://github.com/pmalasp/dtostrf