Q:
Do you have any reference designs that can help me extend the reach of the SPI on the EVAL-ADIS?
A:
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We recently completed a project, where we helped someone establish communication between an ADIS16485 and the EVAL-ADIS evaluation system, which were over 2 meters apart from each other. In addition to the distance, the ADIS16485 was on top of a rotating platform, inside of an temperature chamber, while the EVAL-ADIS was outside of the chamber. Since the remote communication port (J1) on the EVAL-ADIS will only support 12 inches of ribbon cable to a remotely located ADIS1648x, we decided to see if using LVDS signals for the majority of the distance between the sensor (ADIS1648x) and the evaluation system (EVAL-ADIS) could reach the separation goal of at least 2 meters. This approach was very successful, as our first set of PCBs supported nearly 9 meters of separation, without a single bad data point, while sweeping the temperature over a range of -40C to +85C. The following picture illustrates three different PCBs that supported this preliminary test.
This post relates to one of the PCBs in this group: the EVAL-ADIS SPI Extender board. On this board, an ADN4665 provides the LVDS-to-SPI translation for the transmitted signals (chip select, serial clock, data input) and an ADN4666 provides the SPI-to-LVDS translation for the received signals (data output, data-ready).
Please find the file attachment, which contains a file bundle of the electrical schematic, PCB drawing, PCB gerbers, assembly view and bill of materials. We (ADI) do not presently plan to sell this board, but hope that these documents help reproduce this PCB for those who are interested in doing so.
REFERENCES
www.analog.com/ADIS16485
www.analog.com/EVAL-ADIS
www.analog.com/ADN4665
www.analog.com/ADN4666
jchong
Just added revision B of the PCB design/drawings. The changes were fairly minor, mostly associated with silkscreen adjustments on reference designators, which helps with assembly and troubleshooting. Hope that helps!
FYI: The attached drawings were used to procure the printed circuit boards from this provider:
https://www.oshpark.com/
NOTE: This is not an endorsement of this supplier, this is just documenting what we did on this particular project.
Continuing to think on this topic. Ethernet actually uses magnetic components for isolation and balancing, presumably to support the 100m distances available through Cat 6 cable.
http://www.analog.com/media/en/technical-documentation/application-notes/EE-269.pdf
Thanks for the kinds words! Since we exceeded our distance objective by over 4x, I didn't give much more thought to extending the length, but this sounds like an interesting idea. Were you thinking about this type of an approach?
http://www.analog.com/media/en/reference-design-documentation/reference-designs/CN0256.pdf
Thanks for sharing this NevadaMark! This is a useful way of allowing for an IMU in a down-hole (high-temp) test chamber, along with a rotating chamber. Nice work on the slip-ring. Do you think that isolating the LVDS interface would give you a longer reach?
Best,
-Paul