VD56G3 MANUAL_COARSE_EXPOSURE Register Clarification

[astral256]

I have the STEVAL-56G3MAI1 evaluation kit for the VD56G3 image sensor and the STEVAL-EVK-U0I1 to connect and take snapshots from the sensor.  I have been looking into script generation and register setting and I would like to set the exposure time to be a known duration in microseconds.  I referenced UM2602 titled "How to integrate and configure the VD56G3, VD66GY, and VD16GZ devices from a hardware and software perspective", which contains all the register configuration information for this sensor.  Section 14.7.2 of UM2602 is for configuring the manual exposure and it talks about a register called "MANUAL_COARSE_EXPOSURE".  The description of the "MANUAL_COARSE_EXPOSURE" register is "Integration time is controlled by the MANUAL_COARSE_EXPOSURE register. The value is expressed in line equivalent".  The manual also states that the value is a 16-bit unsigned integer.

However, there is no information in the manual for how to configure this value to set the manual exposure in duration in microseconds.  There is a slight reference in section 14.7.5 that setting the register to 21 is equivalent to 161 us, but no additional information for how that was acquired.  Can I assume that each bit in MANUAL_COARSE_EXPOSURE corresponds to 7.66 us, and that for an exposure duration of 500 us I would set the register to 65?  What does it mean when it says that the register value is "expressed in line equivalent"?  Are there additional resources I can look into to clarify any of these questions?

[astral256]

I think I figured out what it means by line equivalent.  You can set the "Line Time" with the "LINE_LENGTH" register in section 13.2 of UM2602.  The default and recommended value for the Line Time is 7.69 us, which corresponds to the extrapolated "line equivalent" calculations I performed from the data in section 14.7.5.

So it is my understanding that every bit placed in the MANUAL_COARSE_EXPOSURE register increases exposure duration by a factor of the Line Time, which can be calculated from the LINE_LENGTH register and overall pixel clock.

[MeganeG · Accepted solution]

Hello,

Yes, indeed. The MANUAL_COARSE_EXPOSURE, expressed in lines, can be converted to microseconds by dividing it by the Line time value used (default is 7.69 µs for a 10-bit ADC mode).

You can also verify the value, expressed in milliseconds, using the PC evaluation software (STSW-IMG501) in the Status panel under ExposureTime.

Thank you, Megane.