Interpret bytes received from bluetooth weight scale device in iOS - ios

Question

I am integrating a weight scale device in our iOS Application. The Device name nutriscale weight scale. I am using apple provided API -CBCentralManager for connecting and getting data from weight scale. I am able to detect services and characteristics of bluetooth device and getting some data from weight scale device after connecting but not able to interpret that data. I am able to get weight if it's below 255 gram. If it goes beyond 255. it gives me weight-255 answer.
Kindly correct me for this.
Here it's my code:
When i call [aPeripheral readValueForCharacteristic:aChar]; A delegate method below is being called.
- (void) peripheral:(CBPeripheral *)aPeripheral didUpdateValueForCharacteristic:(CBCharacteristic *)characteristic error:(NSError *)error {// NSLog(#"Descriptor %#",[characteristic properties]);if ([characteristic.UUID isEqual:[CBUUID UUIDWithString:HELLOBLUETOOTH_CHARACTERISTICS_NAME_UUID]])
{
pName = [[NSString alloc] initWithUTF8String:[[characteristic value]bytes]];
NSError *errorVa;
NSLog(#"KeyfobViewController didUpdateValueForCharacteristic %#", characteristic);
[aPeripheral setNotifyValue:YES forCharacteristic:characteristic];
[self getWeightData:characteristic error:errorVa];
}}
To interpret bytes i wrote this method
(void) getWeightData:(CBCharacteristic *)characteristic error:(NSError *)error{
// Get the Heart Rate Monitor BPM
NSData *data = [characteristic value];// 1
const uint8_t *reportData = [data bytes];
const uint16_t *reportData1 = [data bytes];
uint16_t weightValue = 0;
uint16_t weightValue1 = 0;
if(reportData)
{
if ((reportData[0] & 0x01) == 0) { // 2
// Retrieve the weight from the scale
weightValue = reportData[1];
int result= CFSwapInt16LittleToHost(*(uint16_t *)(&reportData[1]));
}
else
{
weightValue = CFSwapInt32LittleToHost(*(uint32_t *)(&reportData[1])); // 3
int result= CFSwapInt32LittleToHost(*(uint32_t *)(&reportData[1]));
NSLog(#"weightValue1 - %hhu",weightValue);
}
NSMutableArray *arrr = [NSMutableArray new];
uint8_t byte1 = reportData[0];
for (int i = 0; i < 8; i++) {int mask = 1 << i;if ((byte1 & mask) == 0) {[arrr addObject:#"0"];} else {[arrr addObject:#"1"];}}
NSLog(#"values1 - %#%#%#%#%#%#%#%#",arrr[7],arrr[6],arrr[5],arrr[4],arrr[3],arrr[2],arrr[1],arrr[0]);
[arrr removeAllObjects];
for (int i = 0; i < 16; i++) {int mask = 1 << i;if ((weightValue1 & mask) == 0) {[arrr addObject:#"0"];} else {[arrr addObject:#"1"];}}
NSLog(#"values2 - %#%#%#%#%#%#%#%#%#%#%#%#%#%#%#%#",arrr[15],arrr[14],arrr[13],arrr[12],arrr[11],arrr[10],arrr[9],arrr[8],arrr[7],arrr[6],arrr[5],arrr[4],arrr[3],arrr[2],arrr[1],arrr[0]);
// NSLog(#"values0 - %#%#%#%#%#%#%#%#",arrr[0],arrr[1],arrr[2],arrr[3],arrr[4],arrr[5],arrr[6],arrr[7]);
// NSLog(#"values2 - %#%#%#%#%#%#%#%#%#%#%#%#%#%#%#%#",arrr[0],arrr[1],arrr[2],arrr[3],arrr[4],arrr[5],arrr[6],arrr[7],arrr[8],arrr[9],arrr[10],arrr[11],arrr[12],arrr[13],arrr[14],arrr[15]);
}
// Display the weight value to the UI if no error occurred
if( (characteristic.value) || !error )
{ //
NSString *weight = [NSString stringWithFormat:#"%i", weightValue];
if([weight floatValue])
{
NSUserDefaults *defaultObject = [NSUserDefaults standardUserDefaults];
[defaultObject setObject:data forKey:#"data"];
[defaultObject synchronize];
NSString *strWeight=#"";
strWeight = [NSString stringWithFormat:#"%#",weight];
strWeight = [NSString stringWithFormat:#"%.1f",[strWeight floatValue]*0.035274];//
//[self bluetoothResponseToClass];
}
}
return;}
Kindly help me in this code. What am i doing wrong ?

Answer 1

Replace your function with below function
-(void) getWeightData:(CBCharacteristic *)characteristic error:(NSError *)error
{
// Get the Heart Rate Monitor BPM
NSData *data = [characteristic value];// 1
const uint8_t *reportData = [data bytes];
uint16_t weightValue = 0;
uint16_t chkValue = 0;
if(reportData)
{
chkValue = reportData[0];
weightValue = CFSwapInt32LittleToHost(*(uint32_t *)(&reportData[1]));
int var = (chkValue % 160);
weightValue = weightValue + var * 256;
NSMutableArray *arrr = [NSMutableArray new];
uint8_t byte1 = reportData[0];
for (int i = 0; i < 8; i++) {int mask = 1 << i;if ((byte1 & mask) == 0) {[arrr addObject:#"0"];} else {[arrr addObject:#"1"];}}
NSLog(#"values1 - %#%#%#%#%#%#%#%#",arrr[7],arrr[6],arrr[5],arrr[4],arrr[3],arrr[2],arrr[1],arrr[0]);
[arrr removeAllObjects];
for (int i = 0; i < 16; i++) {int mask = 1 << i;if ((chkValue & mask) == 0) {[arrr addObject:#"0"];} else {[arrr addObject:#"1"];}}
NSLog(#"values2 - %#%#%#%#%#%#%#%#%#%#%#%#%#%#%#%#",arrr[15],arrr[14],arrr[13],arrr[12],arrr[11],arrr[10],arrr[9],arrr[8],arrr[7],arrr[6],arrr[5],arrr[4],arrr[3],arrr[2],arrr[1],arrr[0]);
}
// Display the weight value to the UI if no error occurred
if( (characteristic.value) || !error )
{ //
NSString *weight = [NSString stringWithFormat:#"%i", weightValue];
lbl_Weight.text = [NSString stringWithFormat:#"%hu", weightValue];
if([weight floatValue])
{
NSUserDefaults *defaultObject = [NSUserDefaults standardUserDefaults];
[defaultObject setObject:data forKey:#"data"];
[defaultObject synchronize];
NSString *strWeight=#"";
strWeight = [NSString stringWithFormat:#"%#",weight];
strWeight = [NSString stringWithFormat:#"%.1f",[strWeight floatValue]*0.035274];//
//[self bluetoothResponseToClass];
}
}
return;
}