I have a BrickPi+ + RPi 2 configuration with 4x EV3 Ultrasonic sensors and two large EV3 motors. I use the BrickPi python library to connect to the sensors and followed exactly the example code for communicating with the EV3_US sensor. In my case when I sample the sensors through my program I get readings from all of them but only two give meaningful readings (e.g. 40 cms) while the other two give a constant value of 65532. The sensors are placed according to the North-South-East-West directions (each in right angles to adjacent ones).
I ran successfully the example code reading from a single EV3 sensor. I also use the 8x AA battery pack to power the robot and sensors. Researching the problem I found that possibly the problem is related to read-write time parameter of the BrickPi which is set to 7 in the formware. Modifying the time delay period that I allow after each sensor reading from 10 ms to 2 secs didn’t solve the problem. With a value of 1sec delay I can read up to 2x EV3_US meaningful values from the four sensors. For lower or higher values (in the aforementioned range) I can only read one out of the four.
Any help in sorting this problem out will be appreciated.