iOS reading data from bluetooth 4.2 BLE device - ios

Question

I'm trying to read data from a BLE device getting the data from delegate method
- (void)peripheral:(CBPeripheral *)peripheral didUpdateValueForCharacteristic:(CBCharacteristic *)characteristic error:(NSError *)error.
I am reading the data from CBCharacteristic object by using property value.
This returns the NSData.
I converted this NSData to Bytes.
How to Calculate the Weight from this Bytes data?. By this code i am not getting exact value.
Here is MyCode
/** This callback lets us know more data has arrived via notification on the characteristic
*/
- (void)peripheral:(CBPeripheral *)peripheral didUpdateValueForCharacteristic:(CBCharacteristic *)characteristic error:(NSError *)error
{
NSLog(#"peripheral %#", peripheral);
NSLog(#"chacteristic %#", characteristic);
NSLog(#"chacteristic value %#", [characteristic value]);
Response Is Like This
peripheral <CBPeripheral: 0x15e469e90, identifier = A4B7E3A0-A988-02CF-3FAE-3B62056F465B, name = eBody-Fat-Scale, state = connected>
chacteristic <CBCharacteristic: 0x15e250980, UUID = 2A9D, properties = 0x20, value = <0ee803df 07010116 390901ff ff0000>, notifying = YES>
chacteristic value <0ee803df 07010116 390901ff ff0000>
if (error) {
NSLog(#"Error discovering characteristics: %# and %#", [error localizedDescription],[error localizedFailureReason]);
return;
}
int height;
self.targetPeripheral = peripheral;
NSData *tempData=characteristic.value;
NSString *stringFromData = [[NSString alloc] initWithData:characteristic.value encoding:NSUTF8StringEncoding];
NSString *str = [NSString stringWithUTF8String:[tempData bytes]];
NSLog(#"string data %#",str);
NSData *lol = characteristic.value;
NSLog(#"length %lu", (unsigned long)[lol length]);
Byte *byte = (Byte *)[lol bytes];
for(int i = 0;i<[lol length];i++)
{
NSLog(#"Receive byte：%d",byte[i]);
}
/* self.targetPeripheral = peripheral;
NSString *stringFromData = [[NSString alloc] initWithData:characteristic.value encoding:NSUTF8StringEncoding];
NSData *lol = characteristic.value;
Byte *byte = (Byte *)[lol bytes];
for(int i = 0;i<[lol length];i++)
{
NSLog(#"Received bytes：%d",byte[i]);
}*/
if(byte[0] == 0xfc)
{
Byte weightHigh = 0;
if(byte[1] >= 0xc0)
{
weightHigh = byte[1] - 0xc0;
}
else if(byte[1] >= 0x80)
{
weightHigh = byte[1] - 0x80;
}
else if(byte[1]>= 0x40)
{
weightHigh = byte[1] - 0x40;
}
float weightdata = (float)(weightHigh * 256 + byte[2])/10;
NSUserDefaults *prefers = [NSUserDefaults standardUserDefaults];
if([[prefers objectForKey:#"units"] isEqualToString:#"ft"])
{
NSString *weight = [[NSString alloc]initWithFormat:#"%.1f",[UnitParse convertKgToLb:weightdata]];
_weightDataLabel.text = [[NSString alloc] initWithFormat:#"%#",weight];
}
else
{
NSString *weight = [[NSString alloc]initWithFormat:#"%.1f",weightdata];
_weightDataLabel.text = [[NSString alloc] initWithFormat:#"%#",weight];
}
if(weightdata != _lastWeightData)
{
[RCCircleAnimation stopAnimation:_circleImageView.layer];
_lastWeightData = weightdata;
if(weightHigh * 256 + byte[2] == 0x3f*256+255)//overload
{
_weightDataLabel.text = #"overload";
}
else
{
NSThread* myThread1 = [[NSThread alloc] initWithTarget:self selector:#selector(mySoundPlayer)object:nil];
[myThread1 start];
NSMutableDictionary *dic = [[NSMutableDictionary alloc]init];
[dic setObject:[[NSString alloc] initWithFormat:#"%2f",weightdata] forKey:#"Weight"];
NSDateFormatter *formatter = [[NSDateFormatter alloc]init];
[formatter setDateFormat:#"yyyy-MM-dd HH:mm:ss"];
NSString *datestr = [formatter stringFromDate:[NSDate date]];
[dic setObject:datestr forKey:#"TestTime"];
/* // First Time
NSUserDefaults *userDefaults ;
userDefaults = [NSUserDefaults standardUserDefaults];
if ([userDefaults objectForKey:#"UserWeightDataArray"] == nil)
{
[_valuesArray addObject:dic];
[userDefaults setObject:_valuesArray forKey:#"UserWeightDataArray"];
[userDefaults synchronize];
}
else
{
// second Time
[_dateArray addObject:dic];
_finalArray = [[_dateArray arrayByAddingObjectsFromArray:[[NSUserDefaults standardUserDefaults] objectForKey:#"UserWeightDataArray"]] mutableCopy];
[userDefaults setObject:_finalArray forKey:#"UserWeightDataArray"];
[userDefaults synchronize];
}
*/
height = [[[MySingleton sharedSingleton].nowuserinfo valueForKey:#"Height"] intValue];
float bmi = weightdata/((height/100.0f)*(height/100.0f));
_bmiDataLabel.text = [[NSString alloc] initWithFormat:#"%.1f",bmi];
NSLog(#"_weightDataLabel.text %#", _weightDataLabel.text);
[self uploadDeviceInformationToServer:height weight:[[NSString alloc]initWithFormat:#"%.1f",weightdata]];
NSThread* myThread2 = [[NSThread alloc] initWithTarget:self selector:#selector(uploadWeightData:)object:dic];
[myThread2 start];
NSThread* myThread3 = [[NSThread alloc] initWithTarget:self selector:#selector(getAdviceByWeightData:)object:dic];
[myThread3 start];
NSThread* myThread = [[NSThread alloc] initWithTarget:self selector:#selector(sendCloseCmd)object:nil];
[myThread start];
}
}
}
else
{
_lastWeightData = 0;
Byte weightHigh = 0;
if(byte[1] >= 0xc0)
{
weightHigh = byte[1] - 0xc0;
}
else if(byte[1] >= 0x80)
{
weightHigh = byte[1] - 0x80;
}
else if(byte[1]>= 0x40)
{
weightHigh = byte[1] - 0x40;
}
float weightdata = (float)(weightHigh * 256 + byte[2])/10;
NSUserDefaults *prefers = [NSUserDefaults standardUserDefaults];
NSLog(#"data is %#",[prefers objectForKey:#"units"]);
if([[prefers objectForKey:#"units"] isEqualToString:#"ft"])
{
double temp=[UnitParse convertKgToLb:weightdata];
double temp1=[UnitParse convertLbToKg:weightdata];
NSString *weight = [[NSString alloc]initWithFormat:#"%.1f",temp];
NSLog(#"weight in if .... %# and lb is %.1f and kg %.1f",weight,temp,temp1);
_weightDataLabel.text = [[NSString alloc] initWithFormat:#"%#",weight];
}
else
{
double temp=[UnitParse convertKgToLb:weightdata];
double temp1=[UnitParse convertLbToKg:weightdata];
NSLog(#"weight in if .... %f and lb is %.1f and kg %.1f",weightdata,temp,temp1);
NSString *weight = [[NSString alloc]initWithFormat:#"%.1f",temp1];
NSLog(#"weight in else .... %#",weight);
_weightDataLabel.text = [[NSString alloc] initWithFormat:#"%#",weight];
}
// NSString *weight = [[NSString alloc]initWithFormat:#"%.1f",[UnitParse convertKgToLb:weightdata]];
// _weightDataLabel.text = [[NSString alloc] initWithFormat:#"%#",weight];
}
// Have we got everything we need?
if ([stringFromData isEqualToString:#"EOM"]) {
// We have, so show the data,
//[self.textview setText:[[NSString alloc] initWithData:self.data encoding:NSUTF8StringEncoding]];
NSLog(#"GetDataValue : %#",[[NSString alloc] initWithData:self.data encoding:NSUTF8StringEncoding]);
// Cancel our subscription to the characteristic
[peripheral setNotifyValue:NO forCharacteristic:characteristic];
// and disconnect from the peripehral
[self.centralManager cancelPeripheralConnection:peripheral];
}
}
output of bytes data is:
Receive byte：14 byte data is 0xe
Receive byte：176 byte data is 0xb0
Receive byte：4 byte data is 0x4
Receive byte：223 byte data is 0xdf
Receive byte：7 byte data is 0x7
Receive byte：1 byte data is 0x1
Receive byte：1 byte data is 0x1
Receive byte：23 byte data is 0x17
Receive byte：48 byte data is 0x30
Receive byte：17 byte data is 0x11
Receive byte：1 byte data is 0x1

Answer 1

Use this code for read the byte data of weight or heart rate or temperature.
Lol is the nsdata object.
const uint8_t *reportData = [lol bytes];
uint16_t bpm = (uint16_t)reportData;
CGFloat weightdata = 0;
if ((reportData[1] & 0x01) == 0)
{
/* uint8 bpm */
NSLog(#"if reportData is %d",reportData[1]);
bpm = CFSwapInt16LittleToHost(*(uint16_t *)(&reportData[1]));
NSLog(#"if bpm data is %d",bpm);
weightdata = bpm/200.0;
}
else
{
/* uint16 bpm */
NSLog(#"reportData is %d",reportData[1]);
bpm = CFSwapInt16LittleToHost(*(uint16_t *)(&reportData[1]));
NSLog(#"bpm data is %d",bpm);
weightdata = bpm/200.0;
}