CODEWITHSUNDEEP
iosobjective-cintegerhexcore-bluetooth
iosdeveloper
iosdeveloper

Reputation: 99

Parse Characterstic.Value to byte integer format

I am doing the Core Bluetooth application. I am able to connect the peripheral and read, write value from it.

I need to parse the data which I am receiving through characteristic.value to integer format. I had the characteristic value as <011f6d00 00011100 00000000 04050701 05000569 07df0203 020b0d21 02ff33>.

I have divided the data as per understanding. Please help me with the sample code for converting the data. As I am new to iOS observed many links but did not find the exact answer

  <011f6d00 

11 00  event id       //2 bytes

00    event type      //1 byte

00    No of packets            //1 byte

00 00 record count               //2 byte

04 05 total duration            //2 byte

07       sensitivity            //1 byte

01    recording sensitivity   //1 byte

05    expected seizure duration  //1 byte

00    Not used parameter       //1 byte

05    Expected recorded duration     //1 byte

69    not used parameters     //1 byte

07    snooze duration       //1 byte

df    disable watch help button    //1 byte   

02 03  year        //2 byte

02    date of month     //1 byte

0b    day of week      //1 byte

0d    hour             //1 byte

21    minute            //1 byte

02   second             //1 byte

ff33>    crc          //2 byte

Upvotes: 0

Views: 1025

Answers (1)

Larme
Larme

Reputation: 26026

NSData *initialData = [yourCharacteristic value];

A way to parse your data is to use subdataWithRange: method of NSData.

Example:

NSData *startOfFrameData = [data subdataWithRange:NSMakeRange(0, 4)];
NSLog(@"StartOfFrameData: %@", startOfFrameData);
NSData *eventIDData = [data subdataWithRange:NSMakeRange(4, 2)];
NSLog(@"eventIDData: %@", eventIDData);

etc.

Output:

>StartOfFrame: <011f6d00>
>eventIDData: <0001>

Note that I may have reversed the order of eventIDData which range could be (6,2) (instead of (4,2)), but you'll get the whole idea.

Then, you have to "understand" the meaning of the data and find the correct format, example (possible) for eventIDData:

UInt16 eventID;
[eventIDData getBytes:&eventID length:sizeof(eventID)];
NSLog(@"eventID: %d", eventID);

And so on...

If you want to "play" with it without reading again and again the characteristic value each time (which means also connect, etc.), here is a method you can use:

-(NSData *)dataWithStringHex:(NSString *)string
{
    NSString *cleanString;
    cleanString = [string stringByReplacingOccurrencesOfString:@"<" withString:@""];
    cleanString = [cleanString stringByReplacingOccurrencesOfString:@">" withString:@""];
    cleanString = [cleanString stringByReplacingOccurrencesOfString:@" " withString:@""];

    NSInteger length = [cleanString length];
    uint8_t buffer[length/2];
    for (NSInteger i = 0; i < length; i+=2)
    {
        unsigned result = 0;
        NSScanner *scanner = [NSScanner scannerWithString:[cleanString substringWithRange:NSMakeRange(i, 2)]];
        [scanner scanHexInt:&result];
        buffer[i/2] = result;
    }
    return  [[NSMutableData alloc] initWithBytes:&buffer length:length/2];
}

Example use:

NSData *initialData = [self dataWithStringHex:@"<011f6d00 00011100 00000000 04050701 05000569 07df0203 020b0d21 02ff33>"];

That way, you can try parsing your data on an other example/project/beta test code.

Upvotes: 3

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