I am developing a QN9021 peripheral device on IAR ARM 8.11.
I encountered a very strange phenomenon!
I made 2 QN9021 PCBAs (identical PCB and components) .
1st QN9021 PCBA was OK to connect my phone and my phone read/write characteristics. I used 1st QN9021 PCBA to develop/debug my project. The day before yesterday, I found my phone can connect to 1st QN9021 PCBA , but can not get a service list from it anymore.
Today I tried it with 2nd QN9021 PCBA (identical project and obj code), it works! My phone can connect to it, and read/write characteristics as well!
Is 1st QN9021 chip is broken? but 1st QN9021 chip can connect to my phone, the RSSI is the same strong with 2nd QN9021 chip (about -60 dBm). or 1st QN9021 chip is in a accidental bad configuration?