i.MX6D MIPI CSI data rate and frame latency

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i.MX6D MIPI CSI data rate and frame latency

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BobLiu
Contributor I

Hello,

Here are two questions about image sensor data capture via MIPI CSI.

i.MX6D is used for now  and  image sensor is connected to processor via MIPI CSI.

Question 1, data rate

MIPI CSI data rate is 1Gbps described in the datasheet of i.MX6D, while it can only achieve around 500bps in fact. The sensor can support 1.2Gbps actually. When using other CPU, it works fine. Is there any limitation for i.MX6's MIPI CSI?

Question 2, frame latency

Using IO pin to trigger the sensor, the image captured by application has one frame latency, verified by different exposure time. Swapping the sensor with different brand, the same happened. It looks like sensor doesn't matter. But very strange. Does any one has some clue on this?

 

Thanks,

Bob

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3 Replies

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art
NXP TechSupport
NXP TechSupport

1. There is a number of MIPI CSI silicon errata, listed in the i.MX6Dual/Quad
Chip Errata document, available on the processor's Documentation web page:

https://www.nxp.com/products/processors-and-microcontrollers/arm-processors/i-mx-applications-proces...

They potentially may be the cause of slowing down the MIPI CSI interface. Please
check them.

2. The MIPI CSI driver uses so-called double frame buffer scheme. So, after
starting capturing data from sensor, at least one complete frame should be
captured before it becomes available for further processing. That's why this one
frame latency always occurs, regardless of resolution and frame rate.

Best Regards,
Artur

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BobLiu
Contributor I

Hi Artur,

 

Thanks for your reply.

1.Looked through the errata, didn't find the data rate related desciption yet.

2.Is it possible to disable the dobule buffer in i.MX6? Further, does i.MX8 Mini have the same double buffer scheme?

Best Regards,

Bob

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NXP TechSupport
NXP TechSupport

Q. Is it possible to disable the dobule buffer in i.MX6?

A. No, there is no way to disable the double buffer since it would result in consecutive frame data overlapping.

Q. Further, does i.MX8 Mini have the same double buffer scheme?

A. Yes.

Best Regards,
Artur

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