[time-nuts] Ebay FE-5680A Rb: Connections and Features

GandalfG8 at aol.com GandalfG8 at aol.com
Sun Dec 11 19:29:56 EST 2011

In a message dated 11/12/2011 23:01:14 GMT Standard Time, smither at c-c-i.com 

Can  anyone tell me if they ALL have the MAX level shifter/driver chip
>  fitted, even though it may not be connected to the connector ?  I  don't
> want full programmability, just 10 MHz frequency correction.  Perhaps I 
> have to take pot luck when I buy ?  What are my  chances of getting one 
> the 'hidden' RS232 and 1PPS output  ?

For what it is worth, this unit:


appears  identical to the one I purchased four weeks ago.  Same seller, 
same cut  
off PCB, same "extras" thrown in, same price.
The FEI part number you are looking for is 217400-30352-1, it is often  
clearly visible in the auction photos and can be seen in at least one of the  
photos in the above link.
I'm sure all will do what you ask but the biggest problem I found was  
actually getting to talk to the unit, it doesn't give you any feedback if you  
get it wrong, just sits there looking at you.
Data connections are as per the manual, pin 8 of the 9 pin connector on the 
 module goes to pin 3 of the 9 pin RS232 port at the PC, and pin 9 at the  
module goes to pin 2 at the PC. Add the ground connection and that's it.
You will need some software to send the HEX 32 bit signed integer  values 
plus checksum to the unit.
Programs such as Hyperterminal aren't much help here but I found the RS232  
Hex Com Tool from Virtual Integrated Design to be ideal.
A demo version can be downloaded from _http://www.viddata.com/_ 
The demo version times out after 5 minutes but can be restarted immediately 
 so that isn't really a problem.
Settings are 9600 Baud, No Parity, 8 Data Bits, 1 Stop Bit, No Flow  
There's plenty of utilities online to convert decimal to HEX, I  
The checksum is just the XOR of the four 8 bit words and I used Windows  
calculator in programming mode for this, not sure if this is relevant to all  
calculator versions but it is in Win7.
My unit came with an offset of zero, and I'm guessing most others will too  
as they probably weren't ever adjusted in use.
I followed Jose Camara's advice for initial offset testing, and  used 
offset values of +4095 and -4096 to calibrate the frequency adjustment  range 
with the zero offset as a confidence check.
The commands to send these offsets, without storing them, plus the  
immediate effects they had for me, are as follows......
+4095 -- 2E 09 00 27 00 00 0F FF F0 --  10.000,000,023,00 MHz  approx
0000 -- 2E 09 00 27 00 00 00 00 00   --   9.999,999,995,00 MHz approx
-4096 --  2E 09 00 27 FF FF F0 00 F0 --   9.999,999,967,00  MHz approx
Gaps in the command string are for clarity, and not needed when  sending, 
and all marked as approx because I was just looking for ballpark  figures and 
didn't wait too long for them to settle.
>From these results it was easy enough to calculate an initial adjustment  
with corresponding offset,that would get me close to 10MHz,  followed by a  
further correction and offset that got me to 10.000,000,000,1 MHz, give or 
take  all sorts of variables, including the phase of the moon on the next 
Thursday  following....ish:-)
Which I decided wasn't too bad for a first try, and close enough  anyway to 
use the adjust and store command for the same value:-)

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