I made a breakout board for qn9021 using dc-dc converter circuit from the data sheet. From software developers guide, I found that all qn9021 comes with preloaded small bootloader which can be used to flash program over spi or uart. I tried using usb to ttl by setting all the possible baudrates, everytime i got error "connection timed out". What might be the problem. Will it be succesfull if using general arm jtag to program it?