Dwg Number: 100221339

29 March 2019
Email from Hans Thomas

The kearfott has a single bulkhead connector with raw power (which goes to isolated dc dc converters) and various rs232,rs422, and ttl timing & trigger signals on it. To prevent a connector flood or other upstream failure from taking out the ins and/or dvl, we need to electrically isolate these lines from the signal transceivers in the ins housing. So in addition to isolating the 1pps and trigger lines ( which are ttl voltage levels like the edgetech isolator) we need to isolate the serial lines which are rs232 or rs422. We can lay out the high level signal structure on Monday.

---0---

1 May 2019
Specs:
 
1PPS TTL level signal into Kearfott

   Input side may be 3V3, 5V tolerant
   Single ended isolated output 5V TTL

TTL Trigger from MVC to Kearfott

   Isolated and level shifted to RS485 level trigger signal into Kearfott

   3 Hz about 1ms pulse

Bidirectional:

   RS232 level serial line into Kearfott

   RS232 level serial line from Kearfott

  Can be either RS232 or RS422 to Kearfott
  Baud Rate ? 115200
  Handshake lines needed ? NONE

From MVC to Kearfott:

   RS232 GPS  9600 no handshake

From MVC common ground reference for all above signals

Kearfott 5V logic supply to power the board

Level shifters

   LTM2882
   
4 May 2019
Email from Hans Thomas

I would make the board the same size as an ashtech DG-14 - you can get the board mechanicals from the manual.

Also, thinking about it some more, I would make the transceivers on the kearfott side multiprotocol, so we can select between RS232, RS422, and RS485 - this might make the board more useful in other applications, and we have plenty of room.

6 May 2019

Updated block diagram, added schematic sheets
Dims of DG-14:  2.3" x 4.15" ( 58.42mm x 107.05mm )
 4 mt holes, 0.125" dia each located 0.150" ( 4.45mm ) from edges
 
8 May 2019
Meeting w/ Hans Thomas

Use a single ADuM w/ integrated P/S
   Power the ADuM from Kearfott Logic 5V
   Viso from ADuM to power the level shifters
Eliminate the DC-DC Converter

---0---

SPIN NOTES FOR REV B
5 Jun 2019

0  Ensure the Bi_Dir channel works on RS232 and RS485

1  Change all TP_040 to TP_012 Except for POWER and GROUNDS

1  Cap C20 ( ftprt murata_dk1 )

1  Add text all sheets source/destination connections
   n/a  Sh 1 Block Diagram
   1  Sh 2
   1  Sh 3
   1  Sh 4
   1  Sh 5
   1  Sh 6


1  Change title block REV to B all sheets
   1  Sh 1
   1  Sh 2
   1  Sh 3
   1  Sh 4
   1  Sh 5
   1  Sh 6
   1  Cables


1  Add " small " test points to all comms signal lines

1  Text " 3V3 " s/b " 5V " Sh 4, 5, 6

1  Add Zero Ohm Resistor " jumper " U3 pin 19 to U3 pin 3 ( VCC )

1  Cut trace U4 pin 6 to U3 pin 19

1  Add connection U4 pin 6 to U4 pin 20

1  Remove TP7

1  Add Zero Ohm resistor " jumper " U2 pin 19 to U2 pin 3 ( VCC )

1  Remove TP8

1  Add 3 - pin header " jumper " 
   Pin 1 U2 pin 8
   Pin 2 net KFT_BI_RXD
   Pin 3 U2 pin 9

1  Swap connections U6 pins 13 and 8

1  Swap connections U6 Pins 9 and 11

Cables Sheet:

1  Swap pins 2 and 3 on all DB9 connectors

1  J4 eliminate wires on pins 10, 13, 14 and 7
 
1  Add wire colors

1  Add note: REAR VIEW