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IanHarvey / bluepy

Python interface to Bluetooth LE on Linux
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Propagation delay of 70ms when communicating with TI sensortag #202

Open kokalz opened 7 years ago

kokalz commented 7 years ago

Hi all,

I seem to be having a somewhat annoying issue when trying to use the bluepy library with TI CC2650STK sensortag device. I'm sampling the IMU triax signals (3 accelerometer and 3 gyro signals) at the smallest permitted bluetooth connection interval (7.5ms). While the data does come in successfully, I appear to have a constant propagation delay of roughly 60ms in my incoming signal. To verify this I've connected an I2C wired IMU to a same board as the CC2650STK and plotted to incoming signals with their respective timestamps. The results can be seen here: https://i.stack.imgur.com/5ZFC3.png (where orange is CC2650STK wireless signal and blue is MPU6050 I2C wired signal).

Would anyone have any idea at all where this delay might be coming from? I've gone through the TI firmware and cannot find any significant buffering happening on that side, so I thought that the reason might lie somewhere in bluepy/BlueZ.

Thank you for your help!!

maleja22 commented 7 years ago

Hi, I would like to know how to modify the sampling time, since I tried to change it by changing the time between polling but the number of samples does not match the expected ... I appreciate any help in this regard