I am using the HART modem EVAL-AD5700-1EBZ evaluation kit. I use the default configuration of the board (it seems correct for my experimentation). The modem is connected to a HART sensor. I drive the UART of this modem thanks to a FPGA. The FPGA receives correctly data sent by the sensor (I see the CD signal and the RXD data). But I do not see the modulation in the HART_out pin when the FPGA sent a message through the UART. I used the RTS pin (low state to send data). Have you an idea about this issue? Do you know the precise synchronisation of RTS signal with the TXD signal in the UART (this information is not in the datasheet). You can see the behavior of the RTS signal on the chronogramm.