Bug in Heart Rate example

RE: Bug in Heart Rate example

Audience — Tue, 06 Nov 2018 15:02:30 GMT

Alright, I found the bug. It's in the iOS app which incorrectly converts the 2 bytes from the heart rate. My code in Swift 4.2 is now -- I'll leave it to the maintainer of nRF connect to fix it in their example which uses Objective-C:

private func heartRate(from characteristic: CBCharacteristic) -> Int {
 guard let characteristicData = characteristic.value else { return -1 }
 let array = characteristicData.toArray(type: UInt8.self)
 var bpmValue : Int = 0;
 if ((array[0] & 0x01) == 0) {
 // Stored in one byte
 bpmValue = Int(array[1])
 } else {
 //Stored in two bytes
 bpmValue = (Int(array[2]) << 8) + Int(array[1])
 }
 return bpmValue
 }

RE: Bug in Heart Rate example

Audience — Tue, 06 Nov 2018 10:37:00 GMT

Hi,

both compiled the HRM example from scratch using Segger as well as just installed the pre-compiled hex file that is supplied on the webpage (https://www.nordicsemi.com/eng/Media/Files/Getting-Started-with-the-nRF52-DK/nRF52-DK-heartrate-monitor-demo). I also used different BLE apps on my iPhone 7 that support reading the heart rate, and all of them show the same issue. I know that the heart rate is increased in increments of 10 from the code, and given the fact that the heart rate is displayed correctly below 8 bits again indicates that it's probably an encoding issue.

RE: Bug in Heart Rate example

haakonsh — Mon, 29 Oct 2018 10:02:15 GMT

Do you have some details on how we can reproduce your issue? Like, how do you know the simulated hart rate is one less than what is reported in the nRF Connect app?