Below is a short GNU Radio pipeline. Its purpose is to write an impulse
response to a character device node representing an FPGA (which contains
a
4-coefficient lowpass filter), read the FPGA’s output, and store said
output
in a file.
#!/usr/bin/env python
from gnuradio import gr, gru, eng_notation, optfir
from gnuradio import blks
from gnuradio.eng_option import eng_option
import sys
#import math
class filter_impulse_test (gr.flow_graph):
def __init__(self):
gr.flow_graph.__init__(self)
# build graph
zeroes = [0 for i in range(20)]
impulse = [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0,
0, 0, 0]
impulse.extend(zeroes)
src = gr.vector_source_f(impulse, 0)
FPGA_OUT = gr.file_source(gr.sizeof_float, "/dev/MQP_Pipe")
FPGA_IN = gr.file_sink(gr.sizeof_float, "/dev/MQP_Pipe")
scale = gr.multiply_const_ff(1.0/65535.0)
head = gr.head(gr.sizeof_float, 1016)
# file as final sink
file_sink = gr.file_sink(gr.sizeof_float,
“./FPGA_impulse_test.dat”)
# now wire it all together
# WILL NOT WORK SIMULTANEOUSLY. This is resolved in a later
update
with os.fork().
# This version is used for debugging reading from/writing to the
FPGA individually.
# Comment out the first self.connect() to read, and the second
to
write.
self.connect (src, FPGA_IN)
self.connect (FPGA_OUT, file_sink) #Removed 'scale' and 'head'
blocks to ensure they were not
#interfering with
the
file IO.
if name == ‘main’:
fg = filter_impulse_test()
try:
fg.run()
except KeyboardInterrupt:
pass
The pipeline, however, just creates a file and doesn’t write to it,
leaving
a file of 0 bytes. I can confirm that the FPGA is working properly, and
that
GNU Radio is writing properly and making requests to read properly given
the
FPGA driver debugger’s output (screenshots included in this post). The
data
is just not getting from the FPGA to its final destination properly. The
pipeline functioned properly with an earlier version of the driver
(which
did not support simultaneous read/write). While driver help isn’t the
primary focus of this mailing list, I’m fairly confident that portion of
this demo is functioning properly. I was wondering if there were any
limitations to the file_sink processing block that I’m unaware of…
At least, it’d be appreciated if someone could point me to the code for
gr.file_sink() itself. I get lost in the mass of processing blocks that
make
use of it when I try to search for it, and can’t find the file_sink()
block
itself.
~ Francesco
http://www.nabble.com/file/p22366939/writing.PNG writing.PNG
http://www.nabble.com/file/p22366939/reading.PNG reading.PNG
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