ios - Extract and Convert NSData from BLE to Float in Swift -



ios - Extract and Convert NSData from BLE to Float in Swift -

i'm developing ios app handles bluetooth sensortag. sensortag based on ti ble sensortag, had of sensors removed.

in sourcecode of original ios app ti xyz-values calculated follows kxtj9_range defined 1.0 in implementation , kxtj9 accelerometer built on sensortag

+(float) calcxvalue:(nsdata *)data { char scratchval[data.length]; [data getbytes:&scratchval length:3]; homecoming ((scratchval[0] * 1.0) / (64 / kxtj9_range)); }

the info comes hexadecimal "fe850d" , method cutting in 3 parts. i'm trying convert method swift, wrong numbers back

e.g. fe should homecoming around 0.02 objective c code does

my swift code far

class sensor: nsobject { allow range: float = 1.0 var data: nsdata var bytes: [byte] = [0x00, 0x00, 0x00] init(data: nsdata) { self.data = info data.getbytes(&bytes, length: data.length) } func calcxvalue()->float { homecoming ((float(bytes[0]) * 1.0) / (64.0 / range)) } ... }

i believe problem must lie around float(bytes[0]) because makes 254 out of fe whereas scratchval[0] in objectivec around 64

but main problem is, new ios programming when had begin project, chose utilize swift larn , code app it.

right utilize original objective c code ti utilize our sensortag, prefer using swift every part in app.

on current ios , os x platforms, char signed quantity, input fe treated negative number.

byte on other hand alias uint8 unsigned. utilize [int8] array instead same behaviour in objective-c code.

ios swift floating-point type-conversion nsdata

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