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Arduino X labview and number 127

markes51

Hello

I am a newbie , and in my project ( a temperature datalog wireless using arduino and xbee- I don't use lifa interface, just get the packet via Labview standard serial VI).

 

A weird thing happens when the temperature gets the 127 C...the labview freezes...I f the temperature become high, just after 128 it's work again, if is going down , just in 124C is ok again

 

this is the way that i send the packet

int32_t l;

int16_t j;

payload[1] = ( ((l >> 24) & 0x000000FF));
payload[2] = ( ((l >> 16) & 0x000000FF));
payload[3] = ( ((l >> 8) & 0x000000FF));
payload[4] = ( ((l >> 0) & 0x000000FF));
payload[5] = (j >> 8) & 0x00FF;
payload[6] = j >> 0 & 0x00FF;

 

where l = temperatur from thermocouple ( *100)

and j is the ambient temperature(*100)

 

in Labview I use join the numbers and convert l to sgl  and j to int16.( /100 to get the decimals)

 

I believe is some wrong way that I'm putting the bits in the packet...or the conversion in labview.

 

I really search a lot in internet, and saw some guys with this problem with the magical 127 number!!!!!

 

If somebody could get me a idea what is it...I really appreciate?

 

( excuse my bad English..I'm from Brazil)

 

thanks

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  • 0

    Hi,

     

    It seems, that maybe you are using different lenght variables, and using shifting to translate between them, you have to do it carefully, because it can work with unsigned variables, but you shoud take care about it when working with signed variables. Also take care that all the parts consider the data (sended/received) as the same kind of variable.

    I.e. in 8-bit -127 is 0b10000001, and in 16-bit 0b1111111110000001, not so easy to use signed values just with shifting variables.

     

    Hope this helps,

  • 0 in reply to gihu

    Hello Thanks for the reply. These numbers are temperatures ( from sensor and the ambient). Both can go to negative. my packet of payload is this way: uint8_t payload[] = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}; maybe I need to change the uint8_t to int8_t ????  thanks again marques

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