Offsetting the lighthouse deck vertically from the brushless frame.

[cafeciaojoe]

Hello,

I am looking to place a protective cage around the Crazyflie brushless. The cage will obstruct the lighthouse deck in its typically mounted position.

Here are some questions in order of importance.

1 - What sort of modifications to the firmware can I make to offset the lighthouse deck vertically by about 10cm?

2 - After such an offset and subsequent cage mounting, would it be correct to assume that the existing PID settings will need to be changed? If so, would following this excellent PID tuning guide be advised?

3 - Will this fix work for the brushed version?

4 - Will this fix work for other translations or rotations?

Let me know if you need any more information.

Cheers

Joe

[gemenerik]

Hi Joe!

1. The best way to handle the vertical offset is to add it in the measurement model for the sweep angles, specifically in the kalman_core/mm_sweep_angles.c file.
2. Whether you need to re-tune the PID controller depends on how the added cage affects the drone's moment of inertia and overall dynamics. The brushless Crazyflie has significant control authority, so you might find the default settings work fine. However, if you notice instability or degraded performance, re-tuning the PID controller would be a good approach.
3. Yes, these firmware modifications should apply to both the brushless and brushed versions since the Kalman filter is always used with the Lighthouse positioning system, regardless of the Crazyflie variant. Note that the brushed Crazyflie may have more problems with the added mass.
4. If you're referring to translations and rotations of the Lighthouse deck, you can theoretically modify the measurement model to account for any repositioning or reorientation. The model starts by incorporating the Lighthouse sensor’s position and the Crazyflie's orientation, so adjustments can be made at this step to compensate for your specific setup.

Let me know if you need further clarification!

[cafeciaojoe]

Hey Rik!

Thanks so much for this! I will try it out ASAP

Cheers
Joe

[cafeciaojoe]

Hi Rik,

I have come back to this problem with a new question and a clarification.

1 - Connection

From our previous experiments, we managed to wire up the LH to the brushless. But which pins did we use? I have tried the following with no success.

Soldering the four pads on the LH deck (GND, VCOM, RX and TX) to wires that plug into pins L10, R9, L1 and L2 respectively.

These soldering pads broke before I realised that I needed to force the LH driver in the firmware.

I haven't had a chance to solder them back but I have tried mounting the deck with individual pins (see picture below). I also tried with a pin in position R8 for the OW memory.

I have tried these pin configurations with the following firmware configurations (using nconfig)

• stock
• CONFIG_DECK_FORCE="bcLighthouse4"
• CONFIG_DECK_FORCE="bcLighthouse4" and # CONFIG_DECK_BACKEND_ONEWIRE is not set

Last time we used ribbon cable and I remember us agreeing that we could save weight by only connecting the required pins.

What am I missing here?

2 - Firmware modification.

In the post above you say "The best way to handle the vertical offset is to add it in the measurement model for the sweep angles, specifically in the kalman_core/mm_sweep_angles.c file."

However, after going back to my firmware fork after our discussion last year I find that changes were made instead to lighthouse_position_estimation.c

Can you confirm that this is the better option?

My apologies I didn't keep good enough notes!

Best
Joe

[ataffanel]

Hi Joe,

1- You will also need the I2C bus to be connected to the Crazyflie. To be precise, from the schematic you should need:

• On P1: TX, RX, SDL, SDA, GND
• On P2: VCOM, OW

This way, things will work even without hacking the deck detection in the firmware. OW can be disconnected if you force the deck (though, I would intuitively just connect it to avoid extra firmware trick).

2- Yes, your interpretation is correct. Changing the sensor positions in lighthouse_position_est.c provides the offset to the sweep-angle measurement model, so no direct change to mm_sweep_angles.c is required.

Good luck!
/Arnaud