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Remote MPU9255
#1
I would like to place my IMU sensor a couple of meters away from the raspberry pi. 
reason 1: My raspberry and monitor is mounted on a flexible arm, I move it when entering the through the hatch.
reason 2: There is some magnetic interference where the raspberry pi is placed

I have used a lot of I2C sensors earlier, but never used any kind of I2C extension. I believe that the I2C protocol can handle about 1 m cable.

Has anyone moved the IMU? what is the recommended way to connect it?

thanks

Ola
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#2
See if this can help[ you

https://sites.google.com/site/olewsaa/ya...e-extender

Bart
  Reply
#3
(02-10-2020, 04:12 PM)BartStevens Wrote: See if this can help[ you

https://sites.google.com/site/olewsaa/ya...e-extender

Bart

The extender from the previous post works great. I have that on my installation
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#4
Ive been reading and testing with some of these ESP32 boards... This board to board communication via mac address seems very interesting for our uses.
I wonder if it would work to get your IMU away from your Rpi wirelessly.
https://randomnerdtutorials.com/esp-now-...ion-esp32/
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#5
(02-10-2020, 04:12 PM)BartStevens Wrote: See if this can help[ you

https://sites.google.com/site/olewsaa/ya...e-extender

Bart

Thanks! Looks very good!

(02-11-2020, 12:12 PM)rastam4n Wrote: Ive been reading and testing with some of these ESP32 boards... This board to board communication via mac address seems very interesting for our uses.
I wonder if it would work to get your IMU away from your Rpi wirelessly.
https://randomnerdtutorials.com/esp-now-...ion-esp32/

I have worked with those boards in the past. Very different quality and not very stable, at least not in my hands.
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#6
I just bought a couple of these for the very same purpose: https://www.ebay.co.uk/itm/I2C-IIC-Activ...2292264539
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#7
(02-10-2020, 11:35 AM)Ola_H Wrote: I would like to place my IMU sensor a couple of meters away from the raspberry pi. 
reason 1: My raspberry and monitor is mounted on a flexible arm, I move it when entering the through the hatch.
reason 2: There is some magnetic interference where the raspberry pi is placed

I have used a lot of I2C sensors earlier, but never used any kind of I2C extension. I believe that the I2C protocol can handle about 1 m cable.

Has anyone moved the IMU? what is the recommended way to connect it?

thanks

Ola

I would use a longer hdmi cord or display cable and mount the RPI. The reason for this is instead of having one cable flexing all your cables have to flex now. Or use a second RPI as a display and keep the server tucked away nice and safe.
ribbon cable is fine within reason if it does not flex much. I Believe their are systems to extend this distance.

I am curious about how well imu would work via a wireless connection. In my wireless windsensor I had a about 3 to 5 ms lag. That is at the top of the mast and the rpi was under the companion way. If the sensor is closer that could be reduced a bit maybe possible:}
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#8
3-5ms lag would be ok, but is the lag constant like it is from i2c?

I don't really recommend a wireless imu, instead it would be easier to use a second raspberry pi zero running tinypilot in remote client.
  Reply
#9
(02-12-2020, 08:30 PM)seandepagnier Wrote: 3-5ms lag would be ok, but is the lag constant like it is from i2c?

I don't really recommend a wireless imu, instead it would be easier to use a second raspberry pi zero running tinypilot in remote client.

I it jumps around a bit depending where people are in the boat, humidity and what ever can interfere with the wifi signal. It is mounted at the top of the mast so it is approximately 40 - 50 feet from the RPI and threw a few layers of fibreglass. I am using UDP so if i miss one i get the next in 100ms I did not see a drop in the testing and watching it eats time. The slowest part is displaying the data in SK or Opencpn they dont like to display data that fast. Kip was a bit smother..   With the ESP32. masthead unit I did some tests with my phone and could pick up the esp32 from a few hundred feet away.  I Sent 3.3 volts to the davis and used a shorter line in the build but it work with the long one too.
I really don't think an IMU would work as they are little *(cky to work with it seems. I have 2 esp32 in a drawer but they are the clunky non breadboard types. maybe i will wire one up and see.
I will do a test.
Code:
pi@openplotter:~ $ ping 10.10.10.101
PING 10.10.10.101 (10.10.10.101) 56(84) bytes of data.
64 bytes from 10.10.10.101: icmp_seq=1 ttl=255 time=2.93 ms
64 bytes from 10.10.10.101: icmp_seq=2 ttl=255 time=2.08 ms
64 bytes from 10.10.10.101: icmp_seq=3 ttl=255 time=2.09 ms
64 bytes from 10.10.10.101: icmp_seq=4 ttl=255 time=2.37 ms
64 bytes from 10.10.10.101: icmp_seq=5 ttl=255 time=3.45 ms
64 bytes from 10.10.10.101: icmp_seq=6 ttl=255 time=2.04 ms
64 bytes from 10.10.10.101: icmp_seq=7 ttl=255 time=2.37 ms
64 bytes from 10.10.10.101: icmp_seq=8 ttl=255 time=2.24 ms
64 bytes from 10.10.10.101: icmp_seq=9 ttl=255 time=2.21 ms
64 bytes from 10.10.10.101: icmp_seq=10 ttl=255 time=2.68 ms
That is between  and esp8266 and a rpi running openplotter  @ 1 meter not much lag. It was sending data at the time to the rpi.
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