Take a step back, to obeserve! when you see something that isn’t working you take it, break it, make it and bring it to the next level Thats how this project spanned out! making a bluetooth receiver from a fully functional but a physically broken Nokia BH-503 bluetooth headset. Initial steps were to open the bluetooth headset and see the construction. Pretty amazed! Well thought out design I would say, but the product had a lot of problems regarding power. (It is going to be a challenge to charge it because the charger plug is unavailable and microUSB was not in practice when it was sold.) disassembled the panel with buttons unscrew after removing the glue from the ear sponges fully disassembled state The battery is mounted with a dual side stick tape Removing the glued sponge [06.07.2015] Next steps would be shorten the wire, change the charging port to mini usb and test the working. Today I will be testing if the strip down setup. [22.07.2015] The wires are made shorter and soldered together. It looks in good shape. It’s charging. Next step would be solder the 3.5mm jack for speaker input instead of the wires for LR speaker. Soldering the 3.5mm jack in different configurations to get the better output to the 2.1 speakers. Everything works great as far as the normal operation of the headset is concerned. Yay for that! but the output has too much noise and the levels are low that when the volume is increased… Read more
Month: May 2019
LQ and RSSI in Bluetooth Protocol: Principles and Application Scenarios
In the physical layer of the Bluetooth protocol stack, there are two useful parameters: LQI and RSSI. Both are used by the receiver to evaluate the current wireless environment quality (link quality) and guide subsequent actions. However, the calculation principles and application scenarios of these two values differ significantly. LQI (Link Quality Indication) measures the quality of the received signal. The quality of the received signal is estimated by the receiver by comparing the received signal with the ideal signal and calculating the error accumulation value. For example, when using FSK or GFSK modulation, the receiver can compare the frequency of each bit with the expected frequency and accumulate a certain number of symbols (e.g., 64) to obtain the error accumulation value. Therefore, LQI can relatively reflect the current link quality, and its value is smaller when the link quality is better, and larger when the link quality is worse. RSSI (Received Signal Strength Indication) indicates the signal strength, regardless of the signal quality or correctness. LQI does not care about the actual signal strength, but the signal quality is related to the signal strength, as a stronger signal is less susceptible to interference, resulting in a higher “correctness” rate, lower LQI, and better signal quality. The following typical scenarios illustrate the application of LQI and RSSI: Weak signal and strong noise: low RSSI, high LQI Weak signal with little noise: low RSSI, low LQI Strong interference (e.g., jammer): high RSSI, high LQI (i.e., high RSSI does not necessarily mean… Read more