Load code from external MCU to DA14531

Hi,

Our use case is to load application code on to the DA14531 from external MCU each time the device is powered up.

I have followed all the steps as shown in the Datasheet and the application noteAN-B-072but i'm not able to boot the device via SPI, the slave doesn't respond with the ack byte after the transmission of the premable data bytes. I know that posting waveforms with such queries is quite helpful in debugging the problem but each time I probe the pins to my CRO I get a very noisy signal. Is there any specific time that I should send the data? I have currently connected the 3v3 pin of the DA14531 to a GPIO and controlling the power going to it.

On power on of the DA14531, I have put up a delay of 20ms as shown in the application noteAN-B-072and then sending the preamble bytes after which I am continously listening on the MISO line to get the ACK data. Please help me solve this issue asap.