Getting HEX out of a QString and putting 2 Bytes together

SpaceToon

Hi,

I have a sensor that measures the orientation and acceleration in the x, y and z directions and sends them to my PC via BLE. The data that are sent are specified in HEX and packed in a string.
Every two adjacent numbers result in a coordinate (consisting of the least significant byte and the most significant bit)

//Example for acceleration
//xLSB, xMSB, yLSB, yMSB, zLSB, zMSB
"128, 62, 255, 107, 120, 20 "

I save this printout in QT in a QString (called sensorValue). I would now like to save all values in a list (preferably in HEX). I did not find how to do it in HEX, so I have this so far:

   QList<QString> myList = sensorValue.split(",");

Then I want to merge every two neighboring bytes. In C this is done like this:

msbAndLsb= (int16_t)(MSB << 8 | LSB);

So, in my case something like:

msbAndLsbX= (int16_t)(myList[1]<< 8 | myList[0]);
msbAndLsbY= (int16_t)(myList[3]<< 8 | myList[2]);

So how can I do this Shift thing with Qt? And how Can I convert these numbers in HEX so that I can work with it?

mpergand

Hi,

You're talking about HEX but the string contains decimal values ?
You want to save this values in HEX so you want to save it as a string , right ? Hum, i'm not sure :)

Here some code to get what you want as int value:

QByteArray bytes=QByteArray("128, 62, 255, 107, 120, 20 ");
   QList<QByteArray> array=bytes.split(',');

   for(int i=0; i<array.count()/2; i++)
       {
       int v=array[i].toInt()+(array[i+1].toInt()<<8);
       qDebug()<<v;
       }

results:
16000
65342
27647

Carefully check the number of data in the array to prevent index out of bound exception.

[EDIT]
You can use QString in place of QByteArray

WARNING
replace
for(int i=0; i<array.count()/2; i++)
with
for(int i=0; i<array.count(); i+=2)

Thanks @JonB for stated my silly mistake :)

SpaceToon

@mpergand

Thank you very much, it's my fault. Yeah, the numbers are received in decimal. So my aim is to put two adjacent decimals "together" with the shift-oeprator and therefore I thought the numbers have to be converted in HEX.
My only problem is, I did not get negative numbers (for example
If I turn the sensor upside down, I should get a negative number for the negative acceleration, but I don't.) Maybe it has something to do with the conversion?

mpergand

try:

int16_t v=array[i].toInt()+(array[i+1].toInt()<<8);

16000
-194
27647

JonB

@mpergand said in Getting HEX out of a QString and putting 2 Bytes together:

for(int i=0; i<array.count()/2; i++)

Before the OP copies this, don't you mean

for(int i=0; i<array.count(); i += 2)

or have I been staring at this too long?!

mpergand

@JonB said in Getting HEX out of a QString and putting 2 Bytes together:

@mpergand said in Getting HEX out of a QString and putting 2 Bytes together:

for(int i=0; i<array.count()/2; i++)

Before the OP copies this, don't you mean
for(int i=0; i<array.count(); i += 2)
or have I been staring at this too long?!

Damned you're right :)

SpaceToon

Thank you both very much, it worked!