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 Cap C20 ( ftprt murata_dk1 ) Add " small " test points to all comms signal lines