kostoglotov

Project-Specific Question: bridging MIPI to the high speed pins on my Digilent Arty board?

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tl;dr: custom design for MIPI bridge to an Arty with no transceivers, besides coming to my senses, what's the best way to tackle this?

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Summer uni project. My task is getting image data from a MIPI camera sensor (OV5467; the Raspberry Pi camera) into an Arty board. 

No high speed transceiver pins on it, and no native support for interfacing to MIPI. Just the HP IOs on the middle Pmods.

Our fall-back is to just take image data in via the Raspberry Pi and squirt that via UART or SPI into the Arty to demonstrate parallelized image processing.

However, the disparity between input-output rates and the rate at which our configured logic can process the image is so significant, we feel it's a waste of an FPGA.

I have perused XAPP894, IOSelect resources for Artix-7 devices, and the IP catalogs in Vivado for CSI-2 Rx/Tx IP, etc. I think we can get the IP on a uni license.

A faculty member helping us is keen to fabricate a custom PCB for bridging MIPI to other standards (like the LVDS_25 on the Arty). If I can bring him a viable design for this bridge he will get it fabricated. I think he might even take care of the PCB design as long as I can bring him a circuit schematic that will work. 

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My questions to y'all :)

1) should I go with a passive RC network (p10 of XAPP894) for D-PHY compliance or use a vendor-bought bridging IC? 

1a) if an RC network, then how precise/accurate/tolerant do my passive component values need to be?

2) should I be simulating this bridge for signal integrity, say with Ibis in Altium, before submitting the design? (I have zero exposure to Altium, let alone simulating for signal integrity)

3) should we just consider switching to a Zedboard (there are a few floating around upstairs) if it has MIPI D-PHY compliant ports? Or is the challenge of a custom bridge worth it? (I am a virgin with this stuff, very little experience)

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any other advice, comments, recommendations, jibes or anecdotes are more than welcome

Thank you.

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Hi @kostoglotov,

I would suggest to use your fall back plan. The Arty does not have the ability to communicate in LVDS 2.5 nor is the transceiver pins routed. What is the desired data rate? The high speed pmod ports might work with a level shifter. Unfortunately, I do not have experience with designing pcb's or with the MIPI spec so would not have good advice concerning your questions 1 and 2. The Zedboard does not have a MIPI connector but does have some high speed data lines routed to the fmc which can run LVDS 2.5. You would need to research fmc cards that would work for your camera, something like this. We also have the Zybo Z7 which has a similar connector to the Raspberry Pi cameras MIPI connector.

cheers,

Jon

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