Python block help

GNU Radio
1

Hi list,

I am writing a custom python block that should take complex input, check
magnitude of incoming samples and if the magnitude is greater than a
threshold value, the block should pass that sample otherwise the block
just
drop the samples. As this is an arbitrary ratio block I derived it from
gr.block and set_auto_consume(False).

However I get intermittent zeros in output stream of my custom block.
Below
is the code

from gnuradio import gr
import gnuradio.extras
import math
import numpy as np

class sdr_pass_valid(gr.block):
“”"
“”"
def init(self,threshold):
gr.block.init(
self,
name = “VALID”,
in_sig = [np.complex64],
out_sig = [np.complex64],
)
self.set_auto_consume(False)

self.threshold =  threshold
def forecast (self,noutput_items,ninput_items_required):
for i in range(len(ninput_items_required)):
    ninput_items_required[i] = noutput_items

def work(self, input_items, output_items):

    in0 = input_items[0][:len(output_items[0])]
out0= output_items[0]
    nread = self.nitems_read(0) #number of items read on port 0
    ninput_items = len(in0)
j=0
for i in range(0,ninput_items):
    if np.absolute(in0[i]) >= self.threshold :
        out0[j] = in0[i]
        j = j + 1
    self.consume(0,ninput_items)
self.produce(0,len(out0))
    return 0
2

Hi Bob,

I think you’ve introduced the “j” variable to keep count of how many
items you’re going to produce, but then just tell the scheduler you’ve
produced as many items as he offered you to do. Replace
self.produce(0,len(out0))
by
self.produce(0,j).
Also, you consume ninput_items every for loop iteration, so
ninput_items^2 per work run. That’s not right; do it only once, after
the loop.

Greetings,

Marcus