[Discuss-gnuradio] Performing callback function in GRC

[Florian Schlembach]

I am trying to build a flow graph in GNU Radio Companion consisting of a 
USRP source block and a FFT sink. During runtime, I would like to send a 
user settings register to the USRP.
Fortunately, everything is already employed so I only need to build some 
sort of variable control. By now, that already works out quite well 
using the WX GUI Widgets. A user settings command basically be send to 
the USRP using the

void set_user_register(const uint8_t addr, const uint32_t data, size_t 
mboard)

function that is part of the USRP source block. When changing the two 
variables $user_reg_addr and $user_reg_data, GRC invokes the callback 
function that I have defined in the file 
gnuradio/gr-uhd/grc/gen_uhd_usrp_blocks.py:

<callback>set_user_register(\$user_reg_addr, 
\$user_reg_data,uhd.ALL_MBOARDS)</callback>

If I now change either $user_reg_addr or $user_reg_data, the callback 
function is executed, which is not intended. In turn, I first would like 
to execute the callback function after I have modified *both* variables.

Is there a convenient way to execute the callback function on a button 
click or something similar?