Why don't you try the sample "puart_control" app within the SDK on the tag3 board?
...hmm... yes I'll try that.
But I have the feeling it might have something to do with the dip-switches on the board. Do they all have to be "on" or "off"? (SW2 has to be off to start the flashed program...I'm aware of that).
I advanced a little bit with this issue. The configuration of the terminal was not right. I have to use RTS/CTS + XON/XOFF.
I turned this on and suddenly the FTDI forwarded the telegram to the Broadcom chip (at least I see the telegram with an oscilloscope on P33). But the broadcom is still no jumping into any receive interrupt nor do I ever see received data during the application call back (done by the fine timer).
A cycling hw_timer callback transmits data without any problems (via puart_print()...) and sleep is disabled...
I found my mistake!!!
The program I ran was taken from a BCM92737S device. Here the PUart is on Pins 2 and 0. So the p_uart_selectUartPads was still configuring those pins but not P33 and P32....
I changed that and everything works fine now....
thank you for your help. (Bad if the mistake sits a feet away from the monitor...)
Many thanks for the feedback Daniel.