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?
Please be sure you are using the correct pins : QN902x’s PIN0_0 and PIN1_7 are used as UART ISP interface; PIN1_0, PIN1_1, PIN1_2 and PIN1_3 are used as SPI ISP interface.
And yes, standard SWD interface/programmer can be used.
