[Discuss-gnuradio] DBSRX, I2C Interface Verification

[Gregory W Heckler]

I'm in the process of debugging my DBSRX driver, and have verified the 
following:

1) The GC1 input voltage from the aux_dac can be properly commanded. 
Verification was carried out by probing the GC1 pin on the Max2118 chip, 
and observing the voltage sweep from .75 to 2.6 Volts.

2) The enable_refclk and set_refclk_divisor work. This was verified by 
probing the Xtal+ pin on the Max2118 chip, and observing the expected 
clock frequency based on the commanded divisor (4 MHz for a divisor 
value of 16).

3) Read of Max2118 status. After a power cycle reading 2 bytes from the 
I2C interface reports back values of 64, and 127. Reading again results 
in values of 0 and 127 (the PWR status bit has been cleared).

Unfortunately nothing else is working. The charge pump calibration 
procedure keeps failing due to the 3 ADC PLL bits being zero every time 
I read the Max2118 status. I need to verify that the I2C write commands 
are getting through to the Max2118. For the Max2118 3 bytes are written 
over the I2C to write a single register, they are:

1) (Device address<<1) + write bit
2) Register address (0...5)
3) Register value

I noticed that in the python code the first byte is left out, is this 
taken care of by the FPGA? Has anyone tried to turn on the diagnostic 
features of the Max2118 to get a clock signal out of the CNTOUT pin? 
I've tried setting the DIAG value to 6 in order to output the result of 
the R divider onto the CNTOUT pin, but when I probe the pin there is no 
signal. Thanks for any clues.