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Forgot pin number
=====Si5351 Breakout=====
I ordered the board and when it arrived, I attached it to an arduino nano with 5v, GND, SCL and SDA (A4 and A5 on the nano). After programming the board and checking it with my new DSO, it showed 45.55 MHz as programmed using the aforementioned arduino and the Etherkit Si5351 example sketch. I removed the crystal from the LO circuit and attached the Si5351 CLK0 to the collector of Q4 as is done with the original crystal and also grounded the breakout board to the other crystal pad.
Initial tests show nerly nearly identical functionality from stock, even without tuning any filter components onboard. The receiver now responds to signals on 147.350 MHz, comfortably near the top of the 2 meter band.
With that, I taped the arduino and breakout board together, insulated, and hijacked power from the main LM7812 regulator to power it.
The stock DIP switch config for the steady 3 min cycle timer is, from left to right (Up = ON): up, down, up, down, down, up, down, up. This sets pins 1, 3, 6 and 8 high, and 2,4,5,and 7 low (the DIP switch numbers are backwards in reference to the IC pins). This equates to a RC time constant of 165.
Pin 13 of the IC is the RC input which is fed by a 1.1MOhm resistor and a 1uF 35v tantalum capacitor. Cross referencing those values in the datasheet chart, we get a RC timebase of ~1Hz, though measuring via scope it shows the period to be 0.66Hz (1.5sec/cycle exactly). The confusing part is that with these figures, we get a cycle time of 165 ~110 seconds, not 180 as 3 minutes would work out . Still not super clear how this works. <gallery>File:Cdf_timer_rc_scope2.png|Wide view of the RC oscillator via pin 13File:Cdf_timer_RC_scope.png|Decoder modules bottom side (mirrored tomatch top side)</gallery> At low values it seems to be pretty accurate (eg. I will have to try setting switches 5 sec), but with my test of "180s" (8, 6, 5 and 4 high which should equal exactly 180s) yielded approximately 3m18s (almost 200s). Timing the stock setting gets 2m57s, or 177s.
'''U1 ''' - Motorola MC14081BCP<ref>https://www.mouser.com/datasheet/2/308/1/MC14001B_D-2315187.pdf</ref> (B-Series CMOS Quad 2−Input AND Gate)
'''U2 ''' - Motorola MC14011BCP<ref>https://www.mouser.com/datasheet/2/308/1/MC14001B_D-2315187.pdf</ref> (B-Series CMOS Quad 2−Input NAND Gate)
'''U3 ''' - N/A (Populated on other boards)
'''U4 ''' - Maxim ICM7240IPE<ref>https://www.analog.com/media/jp/technical-documentation/data-sheets/1360.pdf</ref> (Programmable Timer/Counter IC)
*'''Left'''
** P1-1:Signal Out to Relay Driver** P1-2:STOP (Local control via terminal strip) I assume this pulls pin 10 of the ICM7240 to GND(?) to reset the chip cycle. COM is referenced to GND on the terminal strip.** P1-3:START (Local control via terminal strip) I assume this pulls pin 11 of the ICM7240 to GND(?) to trigger the cycle.** P1-4:Trigger Input? (Goes to STOP terminal on terminal block as well as P2-4 on decoder module B?)
** P1-5: Vin (+12v)
* '''Right'''
** P2-1: GND
** P2-2:N/C on Main Board** P2-3:Coupled to GND via C44** P2-4:N/C on Main Board** P2-5:N/C on Main Board
File:Cdf_relay_driver_schematic.png|Reverse engineered schematic of the relay driver.
</gallery>
'''Pinout (left to right):'''
*'''Left'''
** P1-1: N/C on Main Board, but traces route to it on driver board
** P1-2: Signal Input from timer
** P1-3: N/C on driver board
** P1-4: N/C on driver board
** P1-5: Vin (+17v)
* '''Right'''
** P2-1: GND
** P2-2: Relay Coil
** P2-3: Relay Coil
** P2-4: N/C on Main Board, but traces route to it on driver board
** P2-5: N/C on Main Board, but traces route to it on driver board
<br />
==General Notes/Things to Watch Out For==