DS90UB962-Q1: TDA4VM + DS90UB962 + DS90UB953 : FPS problem

Sentinen.Chen

Expert 2415 points

Part Number: DS90UB962-Q1
Other Parts Discussed in Thread: TDA4VM

Hi TI members:

We have one TDA4VM customer board, and have one camera AR0820.

We connect this camera to our board, as below setup:

TDA4VM <-- CSI2 --> DS90UB962 <-- FPD-Link3 --> AR0820 with DS90UB953

After I study the datasheet and related thead,

I calculate our fps limit as below:

In CSI2 path between TDA4VM and DS90UB962, our DS90UB962 max speed can achieve 1.664Gbps(= 212992 KB/s),
and AR0820 format is 3840 * 2180 * 12bits (RCCB RAW12 HDR), so one frame size = 12150KB
so fps on CSI-2 path is only 17.5 frams
In FPD-Link3, follow thread, PCLK = (Horizontal Lines + Overhead) x (Vertical Lines +Overhead) x fps
In our board case, we use DS90UB962 connect to DS90UB953, so FPD3 input Mode should set as CSI2-mode ==> FPD3_PCLK = 4 x REFCLK = 4 x 25MHz = 100MHz.then fps = 100MHz / (3840 * 2180 * 1.05) = 11.4,so FPD-Links path only can support to 11.4 frams

But vision_apps document describle that AR0820 can support to 27 Frams In TDA4 EVM board case,

I see vision_apps source code, they use DS90UB960 as deserializer, but the speed limit almost the same between DS90UB960 and DS90UB962.

If EVM can support to 27fps, then our customer board should can support AR0820 camera 27 fps.

But as I calculated, our max frames are only 17 frames on CSI-2 path and 11 frames on FPD3.

Can some help me to figure out is there any error in my fps calculated function?

Sentinen Chen

over 4 years ago

0 Jiashow Ho over 4 years ago

TI__Genius 11340 points

Hi Sentinen,

You can estimate your total input camera bandwidth by using the following equation: 3840*2180*12bpp*27fps*15% overhead = 3.1Gbps. The CSI rate per lane for a 4 lane configuration is 3.1Gbps/4lane = 780Mbps/lane.

As long as your output bandwidth is lower than your input bandwidth, you should be able to output the CSI data.

0 Sentinen.Chen over 4 years ago in reply to Jiashow Ho

Expert 2415 points

Hi Jiashow:

Thanks your information,

It seem I miss to calculate the variable of 4 lane in CSI-2 path between UB962 and TDA4VM.

And how about the FPD3 PCLK limit of each lane? One FPD3-Link only have one lane.

Sentinen Chen

0 Jiashow Ho over 4 years ago in reply to Sentinen.Chen

TI__Genius 11340 points

Hi Sentinen,

In the context of CSI-2 data, we don't usually refer to the term PCLK. Are you asking for the number of lanes the FPD-link protocol runs at? The FPD-Link supports one cable per port so it will be one link.

0 Sentinen.Chen over 4 years ago in reply to Jiashow Ho

Expert 2415 points

Hi Jiashow:

Yes, I am asking about this part "DS90UB962 <-- FPD3-Link --> AR0820 with DS90UB953".

Because even the path form DS90UB962 to TDA4VM can achieve 27fps,

but if the max speed of each FPD3-Link cable only support to 11 fps,

then in signal camera case, the total fps of AR0820 can't achieve 27 fps, right?

Sentinen Chen

+1 Jiashow Ho over 4 years ago in reply to Sentinen.Chen

TI__Genius 11340 points

Hi Sentinen,

Frame rate is just one factor that impacts the CSI rate. We need to know the actual CSI rate of each configuration to be able to tell whether it will be supported or not. The 953 can support up to 800Mbps/lane for a four lane config when you have a 25MHz on the deserializer side.

Best,

Jiashow

+1 Sentinen.Chen over 4 years ago in reply to Jiashow Ho

Expert 2415 points

Hi Jiashow:

Thanks your information about UB953,

and I find I am into the misunderstanding,

I should use Foward channel rate to calculate FPD-LinkIII ability, not PCLK.

so the max speed of should as below status

TDA4VM <-- CSI2( 780Mbps/lane ) --> DS90UB962 <-- FPD-LinkIII (FC Rate is 4 Gbps) --> DS90UB953 <-- CSI2(800Mbps/lane) --> AR0820 sensor.

For this config, it seem AR0820 27fps should be OK.

Sentinen Chen

Interface

Interface forum

DS90UB962-Q1: TDA4VM + DS90UB962 + DS90UB953 : FPS problem