Re: [Discuss-gnuradio] digital noise input

[Oussama Sekkat]

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

On 11/11/06, Eric Blossom <address@hidden> wrote:

On Fri, Nov 10, 2006 at 07:23:07PM -0800, Oussama Sekkat wrote:
> On 11/10/06, Eric Blossom <address@hidden > wrote:
>
> Yes, I could enable the output pins from the host and just connect the
> rx_a_a to one of the debug inputs in the master_control module. I thaught it
> wouldn't make a difference if I just connect it directly to the DEBUG pins.
> Or does it?

It depends on whether or not you need to be able to control the
attached daughterboard too.

> >I then load the .rbf file to the FPGA, connect the io_rx_a outputs of the
> >> LFRX daughter board to the logic analyzer and observe what I get. I make
> >> sure that no antenna is connected to the RX-A port.
> >> To my surprise, some of the upper bits toggle. For example, bit 11, 10,
> >9,
> >> 8, 5 ,4 , 3 ,2 ,1 0, toggle. Since I should only be getting noise, I was
> >> expecting to get a very low signal where only the least significant bit
> >> would be switiching between low and high values.
> >
> >Are they being driven or are they just floating?
>
> No antenna is connected to the RX-A and RX-B ports , so those are floating.


> But the debug pins are connected to the logic analyzer. (I am not sure if I
> answered you're question, when you say "they" are you referring to the DEBUG
> pins or the input ports? )

No, not the antenna, the i/o pins.  My guess is that you haven't
output enabled them.

Eric