April Tag and Multiple Cameras Question

Project Discussion
1

I have 2 H7s with MT9M114s with the 2.1mm lens.

FRC is using 16H5 “8x8” tags (the black region is 6x6, so are they really 6x6 or 8x8?)

I’m having trouble with the calculations for the transforms. My understanding is that I should use the following for fx and fy:
f_x = (2.1 / 2.46) * 160 # QQVGA
f_y = (2.1 / 1.85) * 120 # QQVGA

But my xyz distance vector seems very off. How do I account for the tag size?

Also, I’m thinking about using 2 cameras on the robot this year. what is the best way to feed there data into the roborio? The rio has 2 I2C buses, 2 SPI buses, and 2 UART (1 is USB UART and the other is normal). I’m wondering if I should daisy chain them into the normal UART or if I should have an ESP32 or something to pull them in and fuse the data and then feed that to the RIO.

2

That example was made for a different image sensor. The OV7725. So, you need to use different numbers. Please see the sensor data sheet and lookup the image sensor pixel array size in mm.

Use the UART. This is the most reliable.

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3

I think these are the right numbers. Is the resulting xyz in meters or mm?

4

Could I use CAN?

5

Can also works. You need to purchase the CAN shield.

The resulting xyz will be unit less I think. You need to convert those into real numbers. It’s just a scale factor which is pretty easy to determine through actual measurement.

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6

image
image636×769 119 KB

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7

Yup, I’m using those numbers.