Issue with recognizing the start bit in the preamble of AD5700

Here are oscillograms at different points in the circuit

Hi DKhrip ,

Apologies for the delay, do you still need help with this query?

Things you could try to do:

1) monitor the CD pin to make sure that carrier detect works well at the start of your preamble (similar to Figure 5 of the data sheet)

2) use the part in DUPLEX mode just to test a different HART source

Looking at the HART signal though, they don't look like close to sine wave. The waveshape affects how the demodulator detects and demodulate the signal as it goes through series of filters within the device. 

Could you review of the waveshape is within specifications of HART physical layer?

Hi DKhrip ,

Apologies for the delay, do you still need help with this query?

Things you could try to do:

1) monitor the CD pin to make sure that carrier detect works well at the start of your preamble (similar to Figure 5 of the data sheet)

2) use the part in DUPLEX mode just to test a different HART source

Looking at the HART signal though, they don't look like close to sine wave. The waveshape affects how the demodulator detects and demodulate the signal as it goes through series of filters within the device. 

Could you review of the waveshape is within specifications of HART physical layer?