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High speed 4x RJ45 with quad LVDS each
Design files (schematics, PCB layouts, BOMs) can be found at DIO_RJ45/Releases.
DIO_RJ45 is an extension module supplying 16 LVDS pairs via 4 front-panel RJ45 connectors. This board connects to up to two EEM headers but single-header operation is also possible, with limited number of 8 IOs.
Each RJ45 supplies 4 LVDS DIOs. The direction (input/output) is individually selectable for each signal via I2C or on-board switches. Outputs are intended to drive 100Ohm loads (LVDS is short-circuit protected), inputs are 100Ohm terminated. The connectors dedicate all 8 pins to LVDS signals, ground is on the connector shield so ** only shielded Ethernet cat 6 ** shielded cables are allowed. Maximum verified operating frequency is 150MHz due to TTL generator limitation. IO buffers used in the design permit operation with much higher frequency.
RJ45 pins:
| Function | Comment | Pin(s) | pin designation if used for SPI |
|---|---|---|---|
| GND | shield | ||
| LDVS_1 | LVDS, bi-directional | 1 (P), 2 (N) | SCLK, clock-capable |
| LDVS_2 | LVDS, bi-directional | 4 (P), 5 (N) | MOSI |
| LDVS_3 | LVDS, bi-directional | 3 (P), 6 (N) | MISO |
| LDVS_4 | LVDS, bi-directional | 7 (P), 8 (N) | CS |
