Nokia FYGM HDMI Pinout

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Signal descriptions:
  * GPS_TIME_IN_H, GSM_FC_IN_H, GPS_TIME_IN_L, GSM_FC_IN_L: serial datafrom GPS to CPU or GSM Frame Clock input; RS422/485 differential
  * SingleEndedIn: REF2M_IN REF10M_IN Accepts TTL/CMOS and SINE from -6 to+13 dBm. Input impedance is approximately 75 Ohm, Reduced swing TTL resultingfrom TTL-Gate plus 75 Ohm source termination is OK, too.
  * NC: No Connection
  * GPS_PPS_IN_H, GSM_FN_IN_H, GPS_PPS_IN_L, GSM_FN_IN_L: PPS pulsefrom GPS or GSM Frame Number input; RS422/485 differential
  * GPS_CONTROL_H, GPS_CONTROL_L: Serial data form CPU to GPS; RS422/485differential.
  * GPS_PWR, GPS_PWR_RET: GPS power supply: 50 mA at 15 to >35 VGPS_PWR_N might not be isolated from GND but cannot be relied upon to be thesame.

^ Pin  ^ Signal         ^ Notes              ^
| 1    | GPS_TIME_IN_H  | UART from GPS      |
| 2    | SingleEndedIn  |                    |
| 3    | GPS_TIME_IN_L  | UART from GPS      |
| 4    | GND            |                    |
| 5    | NC             |                    |
| 6    | GND            |                    |
| 7    | GPS_PPS_IN_H   | PPS Pulse          |
| 8    | NC             |                    |
| 9    | GPS_PPS_IN_L   | PPS Pulse          |
| 10   | GPS_CONTROL_H  | UART input to GPS  |
| 11   | GND            |                    |
| 12   | GPS_CONTROL_L  | UART input to GPS  |
| 13   | GND            |                    |
| 14   | NC             |                    |
| 15   | GPS_PWR_RET    | 15-35v             |
| 16   | GND            |                    |
| 17   | GND            |                    |
| 18   | GPS_PWR        | 15-35v             |
| 19   | NC             |                    |

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  * https://www.maximintegrated.com/en/products/interface/transceivers/MAX490.html
  * https://www.ebay.com/itm/RS422-Mutual-transfer-TTL-bi-directional-Signal-Module-Full-duplex-422-to-s-B4A9/173631547293