# Configuring battery monitor with FPV ESC

Source: https://forum.modalai.com/topic/3342/configuring-battery-monitor-with-fpv-esc
Category: General Questions (https://forum.modalai.com/category/2/general-questions)
Posted: 2024-04-18 23:27:19 UTC by restore
Replies: 20 · Views: 5869

## restore · 2024-04-18 23:27:19 UTC

Hi we have configured and calibrated our Voxl FPV ESC 4 in 1 to run our T Motor MN5006 450KV motors but have not been able to get battery monitor working. I've tried all options in /etc/modalai/voxl-px4.config

Running voxl-inspect-battery results in NA values in all the fields. There is also no Mavlink message for battery monitor.

Edit: this is on a VOXL2 mainboard.

## Reply by Moderator (ModalAI staff) · 2024-04-19 01:55:11 UTC

@restore The FPV ESC power monitor should work just like the Mini 4-in-1 ESC power monitor https://docs.modalai.com/voxl2-mini-offboard-sensors/#power-monitoring

## Reply by Alex Kushleyev (ModalAI staff) · 2024-04-19 02:39:14 UTC

@restore , please make sure the `voxl_esc` px4 driver is running and `VOXL_ESC_PUB_BST` px4 parameter is set to 1 . here is a link to the param definition : https://github.com/modalai/px4-firmware/blob/voxl-dev/src/drivers/actuators/voxl_esc/voxl_esc_params.c#L234

What version of PX4 are you running? I just want to make sure that has the functionality for battery reporting from the mini and FPV ESCs.

## Reply by Alex Kushleyev (ModalAI staff) · 2024-04-19 02:40:53 UTC (in reply to Alex Kushleyev)

Additionally, since you are using a relatively low kV motor, please review the following document that helps to make sure you adjust ESC parameters to avoid desync (and test to confirm) : https://gitlab.com/voxl-public/voxl-sdk/utilities/voxl-esc/-/blob/master/voxl-esc-tools/doc/low_kv_motor_tuning.md

## Reply by Dan Jennings · 2024-04-19 05:37:26 UTC (in reply to Alex Kushleyev)

@Alex-Kushleyev 
Thank you for the instructions, I will look into those tomorrow. 

We have the ESC plugged into Voxl2 J18 as indicated in the VOXL2 ESC configs

Low KV guidance is very welcome. We were having trouble getting the motors to work and looked into the param files to try and figure out what was wrong. Changing the KV made motor response much better. We have good motor behavior now but I'll go through those instructions to be sure the motors are properly tuned.

## Reply by Alex Kushleyev (ModalAI staff) · 2024-04-19 13:07:08 UTC (in reply to Dan Jennings)

@Dan-Jennings, you are welcome. Just one note about the low kv tuning, instructions say set this param to 1 (demag_timing: 1 ), but leave it off (at zero). I will correct the doc - this was an experimental feature, you should not need. Also instructions say to use m0134-6 esc, but the FPV esc is just fine for this purpose. You can keep your existing tuning file and check the parameters that are suggested in the guide.

## Reply by restore · 2024-04-19 18:31:55 UTC

PX4 version 1.14.0-2.0.68
VOXL_ESC_PUB_BST is enabled
Voxl-esc is running, can spin and calibrate motors.

Still no battery monitor

Low KV tuning worked, motors responding well.

## Reply by Alex Kushleyev (ModalAI staff) · 2024-04-19 20:52:43 UTC (in reply to restore)

@restore , This should be the correct PX4 version (it has support for this feature)

When you start PX4, are the blue LEDs on the ESC blinking? if not, then PX4 is not communicating with the ESC, you may need to double check the baud rate setting (baud rate in ESC params needs to match the VOXL_ESC_BAUD. 

Related question, is the actuator test in PX4 working?

Alex

## Reply by Dan Jennings · 2024-04-19 23:14:21 UTC (in reply to Alex Kushleyev)

@Alex-Kushleyev 
Yes, ESC is working, we're able to calibrate ESCs using esc tools, spin up motors in QGC, and have flown several times. Just having to be very conservative without battery status.

## Reply by Alex Kushleyev (ModalAI staff) · 2024-04-19 23:39:00 UTC (in reply to Dan Jennings)

@Dan-Jennings,

We will figure it out :) quick question - what baud rate are you using for the ESC and also esc firmware version / hash? I will test with exact version of esc firmware and px4.

If your baud rate is 250k, please change it to a higher value, we typically use 2M. If baud rate is too low, may not be fast enough to send the extra packet with total current.

## Reply by Alex Kushleyev (ModalAI staff) · 2024-04-19 23:52:14 UTC (in reply to Alex Kushleyev)

Another question - when you use voxl-esc tools and spin id 2, do you get a total current measurement printed in terminal along with regular esc feedback?

## Reply by Alex Kushleyev (ModalAI staff) · 2024-04-22 19:58:44 UTC (in reply to Alex Kushleyev)

@Dan-Jennings , did you figure out this one?

the way the battery publishing works on M0138 (FPV) ESC and M0129 (Mini) ESC is as follows:
- one of the MCUs on the ESC is hooked up to the total current sensor. On M0138 it is ID2, on M0129 it is ID3
- when flight controller requests feedback from the ESC (by setting appropriate bit in the commanded RPM or Power control packet), the ESC ID with the current measurement will send out its regular feedback packet and right after the special battery status packet
- this battery status packet is received and parsed by PX4 and if the `VOXL_ESC_PUB_BST` px4 param is set to 1, the battery status is published, code [here](https://github.com/modalai/px4-firmware/blob/voxl-dev/src/drivers/actuators/voxl_esc/voxl_esc.cpp#L565)
- this only happens if `voxl_esc` px4 driver is running and and it is communicating with the ESC (e.g. UART baud rate is correct). You will see the ESC flash all 4 blue leds, which means the commands (disarmed rpms = 0 if not in flight) are received from the PX4 flight controller
- you can view the battery status message in VOXL2 terminal using the following command:
```
px4-listener battery_status
``` 
I hope this helps!

Alex

## Reply by Dan Jennings · 2024-04-24 18:01:06 UTC (in reply to Alex Kushleyev)

@Alex-Kushleyev still pending on this. Have had other issues to solve. Will be starting another thread shortly.

## Reply by restore · 2024-05-30 23:11:12 UTC (in reply to Alex Kushleyev)

@Alex-Kushleyev 

We're finally rebuilt and recalibrated, but still no battery status. All 4 blue LEDs are flashing on the ESC, so the voxl_esc px4 driver should be running but we get:
```
voxl2:/$ px4-listener battery_status
never published
```
Where would that PX4 param be located?

## Reply by Alex Kushleyev (ModalAI staff) · 2024-05-30 23:13:26 UTC (in reply to restore)

@restore , can you please check which version of voxl-px4 you are using? You can use “voxl-version” tool.

## Reply by restore · 2024-06-03 18:55:23 UTC (in reply to Alex Kushleyev)

@Alex-Kushleyev 
We are using px4 version  1.14.0-2.0.68
I connected to px4 with QGC and was able to confirm that  VOXL_ESC_PUB_BST is enabled. It'd still be handy to know where those params are stored so we can edit them while connected through adb.

Thanks

## Reply by tom (ModalAI staff) · 2024-06-03 19:03:51 UTC (in reply to restore)

@restore The px4 parameters are stored in a binary file at `/data/px4/param/parameters` so you can't modify that file directly.

However you can use the following to set a param:

```
px4-param set PARAM_NAME PARAM_VALUE
```

or view parameters with

```
px4-param show
```

## Reply by Alex Kushleyev (ModalAI staff) · 2024-06-03 19:24:06 UTC (in reply to tom)

@restore, also can you please check which version of ESC firmware you are running on the FPV ESC? you can do this using voxl-esc tools (while px4 is not running). `voxl-esc scan`

I suggest to update to the latest ESC firmware in voxl-esc repository (dev branch).

## Reply by restore · 2024-06-03 20:15:03 UTC (in reply to Alex Kushleyev)

@Alex-Kushleyev 
ESCs are firmware version   39, hash 17d64675
I checked ```/usr/share/modalai/voxl-esc-tools/firmware``` and the M0138 firmware matches the one [here.](https://gitlab.com/voxl-public/voxl-sdk/utilities/voxl-esc/-/blob/dev/voxl-esc-tools/firmware/modalai_esc_firmware_m0138_1_v0_39_RC11_17d64675.bin)

```
modalai_esc_firmware_m0138_1_v0_39_RC11_17d64675.bin
```

## Reply by Alex Kushleyev (ModalAI staff) · 2024-06-03 21:45:49 UTC (in reply to restore)

@restore, thank you for checking.

Let's do another test:
- for safety, remove propellers from motors
- with px4 disabled, go to `/usr/share/modalai/voxl-esc-tools` on voxl2
- run: `./voxl-esc-spin.py --id 2 --power 0` -- this will send a zero power command to ESC ID 2 (which measures the total current and sends back the battery status message). Motors will not spin. This will also request the battery status and you should see output (if possible you can use the latest voxl-esc tools from dev branch from (https://gitlab.com/voxl-public/voxl-sdk/utilities/voxl-esc/-/tree/dev) since I am not sure which voxl-esc version is installed on your board).

```
./voxl-esc-spin.py --id 2 --power 0
...
Found voxl-esc tools bin version: 1.6
VOXL Platform: M0054
Detected RB5 Flight, VOXL2 M0054 or M0104!
...
...
	Board      : version 42: ModalAi 4-in-1 ESC (M0138-1)
...
...
[0.017] (2) RPM: 0, PWR: 0, VOLTAGE: 15.612V, TEMPERATURE: 35.87C, CURRENT: 0.000A, BOARD_VOLTAGE: 15.612V, BOARD_CURRENT: -0.232A
[0.034] (2) RPM: 0, PWR: 0, VOLTAGE: 15.609V, TEMPERATURE: 35.88C, CURRENT: 0.000A, BOARD_VOLTAGE: 15.609V, BOARD_CURRENT: -0.200A
[0.060] (2) RPM: 0, PWR: 0, VOLTAGE: 15.610V, TEMPERATURE: 35.86C, CURRENT: 0.000A, BOARD_VOLTAGE: 15.610V, BOARD_CURRENT: -0.248A
[0.080] (2) RPM: 0, PWR: 0, VOLTAGE: 15.618V, TEMPERATURE: 35.85C, CURRENT: 0.000A, BOARD_VOLTAGE: 15.618V, BOARD_CURRENT: -0.224A
[0.095] (2) RPM: 0, PWR: 0, VOLTAGE: 15.612V, TEMPERATURE: 35.87C, CURRENT: 0.000A, BOARD_VOLTAGE: 15.612V, BOARD_CURRENT: -0.272A
[0.120] (2) RPM: 0, PWR: 0, VOLTAGE: 15.608V, TEMPERATURE: 35.90C, CURRENT: 0.000A, BOARD_VOLTAGE: 15.608V, BOARD_CURRENT: -0.240A
[0.134] (2) RPM: 0, PWR: 0, VOLTAGE: 15.612V, TEMPERATURE: 35.92C, CURRENT: 0.000A, BOARD_VOLTAGE: 15.612V, BOARD_CURRENT: -0.264A
[0.160] (2) RPM: 0, PWR: 0, VOLTAGE: 15.613V, TEMPERATURE: 35.90C, CURRENT: 0.000A, BOARD_VOLTAGE: 15.613V, BOARD_CURRENT: -0.248A
[0.174] (2) RPM: 0, PWR: 0, VOLTAGE: 15.608V, TEMPERATURE: 35.92C, CURRENT: 0.000A, BOARD_VOLTAGE: 15.608V, BOARD_CURRENT: -0.168A
```
note that there are `BOARD_VOLTAGE` and `BOARD_CURRENT` printed, which are parsed from the battery status message coming from the ESC ID2. Please note that the current around 0 is not very accurate due to a very large measurement range (showing -0.2A, but the discharge current should really be positive based on our convention).

Alex

## Reply by restore · 2024-06-06 20:44:08 UTC (in reply to Alex Kushleyev)

@Alex-Kushleyev 
Thanks for the help, as I was calibrating the ESCs I did notice those messages, which confused me as to why we weren't able to get that information in PX4. On Monday it suddenly just started working despite my changing nothing. Gotta love when things fix themselves