Re: [Discuss-gnuradio] digital noise input

[Eric Blossom]

On Fri, Nov 17, 2006 at 07:13:05PM -0800, Oussama Sekkat wrote:
> Hi,
> 
> I am still trying to measure the digital output noise (from the LFRX_A
> daughterboard).
> In the verilog code I made sure to connect the rx_a_a input to the debug1
> input of the master control module
>   master_control master_control
>     ( .master_clk(clk64),.usbclk(usbclk) .......
>      ............ .debug_1(rx_a_a),.debug_0(ddc0_in_i)........);
> 
> then my python code looks like the following:
> 
> u = usrp.sink_c(0, 64, fpga_filename="usrp_test.rbf")
> side = 0  # side A
> u._write_oe(side, 0xffff, 0xffff)     # set all i/o pins as outputs
> u._write_fpga_reg(FR_DEBUG_EN, bmFR_DEBUG_EN_RX_A)
> 
> I then connect the io_rx debug outputs of side A to the logic analyzer. (no
> antenna is inserted)
> I was expecting to get some noise , but I get a 0 signal ( 16 bit zeroes :(
> )
> 
> Any ideas on why this is happening? Any suggestions?
> 
> Thank you ahead of time.
> 
> Oussama

You have opened the Tx side (the sink), and output enabled the pins on
the side A Tx daughterboard.  Then you've connected your logic
analyzer to the side A Rx daughterboard.  Those pins are not output
enabled. 

Eric