Motherboard Re-Clocking Question

Hi All,

I am working on re-clocking the motherboard to 52MHz. I changed the
oscillator to 52MHz. I followed the instructions on page
http://www.gnuradio.org/trac/wiki/UsrpFAQ/Clocking to change the
gnuradio code.

In usrp_basic.h changed from

long fpga_master_clock_freq () const { return 64000000; }

to
long fpga_master_clock_freq () const { return 52000000; }

In gr-usrp/src/db_flexrf_mimo.py changed from
class db_flexrf_2400_tx_mimo_b(db_flexrf_2400_tx):
def init(self, usrp, which):
db_flexrf_2400_tx.init(self, usrp, which)
self.R_DIV = 16

def _refclk_divisor(self):
“”"
Return value to stick in REFCLK_DIVISOR register
“”"
return 1

class db_flexrf_2400_rx_mimo_b(db_flexrf_2400_rx):
def init(self, usrp, which):
db_flexrf_2400_rx.init(self, usrp, which)
self.R_DIV = 16

def _refclk_divisor(self):
“”"
Return value to stick in REFCLK_DIVISOR register
“”"
return 1

to
class db_flexrf_2400_tx_mimo_b(db_flexrf_2400_tx):
def init(self, usrp, which):
db_flexrf_2400_tx.init(self, usrp, which)
self.R_DIV = 13

def _refclk_divisor(self):
“”"
Return value to stick in REFCLK_DIVISOR register
“”"
return 1

class db_flexrf_2400_rx_mimo_b(db_flexrf_2400_rx):
def init(self, usrp, which):
db_flexrf_2400_rx.init(self, usrp, which)
self.R_DIV = 13

def _refclk_divisor(self):
“”"
Return value to stick in REFCLK_DIVISOR register
“”"
return 1

But when I run program benchmark_tx.py -f 2.5G (I’m using db rfx2400),
the program report the error as follow:
python: usrp_standard.cc:704: virtual bool
usrp_standard_tx::set_tx_freq(int, double): Assertion `dac_freq () ==
128000000’ failed.
Aborted

when I remove the assert in usrp_standard.cc:704. the program report
the error as follow:

Failed to set Tx frequency to 2.4G
Traceback (most recent call last):
File “./benchmark_tx.py”, line 134, in
main()
File “./benchmark_tx.py”, line 97, in main
tb = my_top_block(mods[options.modulation], options)
File “./benchmark_tx.py”, line 42, in init
self.txpath = transmit_path(modulator, options)
File
“/root/gnuradio/gnuradio-3.1.3/gnuradio-examples/python/digital/transmit_path.py”,
line 79, in init
raise ValueError
ValueError

I am appreciate if anyone can give me some guide to re-clocking the
motherboard to 52MHz

Scott

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