We are using the Invensense MPU6050 IMU on I2C with Beaglebone Black (Angstrom 3.8.13). We can use I2C-tools and file I/O thru /dev/i2c but the read speed is disappointingly slow. We only read the 3x gyros and 3x accels (each one byte at a time plus the 2 byte temperature reading) and it takes ~2msecs. My estimate of the I2C bus cycles for a block read suggests this should take ~160 bus cycles or .38msec on a 400MHz I2C bus.
The distribution includes the Invensense driver inv-mpu6050.ko but there is no indication that reading through /dev/i2c invokes it. This is a very popular IMU and Invensense widely distributes the driver over many Linux platforms. The driver source includes “successful installation will create two directories under /sys/bus/iio/devices” and lists the files there (aka functions). I can never get these to show up. I can “insmod /lib/modules/3.8.13/kernel/drivers/iio/imu/inv_mpu6050/inv-mpu6050.ko” and “echo inv-mpu6050 0x68 > /sys/class/i2c-adapter/i2c-1/new_device”. This causes a new directory named 1-0068 to show in /sys/class/i2c-adapter/i2c-1with entries like name and modalias but no functions. It never shows in /sys/bus/iio/devices. What constitutes “successful installation”? What else is needed to get the inv-mpu6050 to expose functions in /sys/bus/iio/devices like the driver sources says? Beaglebone Black uses bone_capemgr for exposing driver functions for many devices. “echo inv-mpu6050 0x68 > /sys/devices/bone_capmgr.9/slots” raises the gripe “write error: no such file or directory”. (I can successfully load the am33xx_pwm driver this way.) Is this because there is no matching DT fragment in /lib/firmware? Is the inv-mpu6050 driver supposed to be invoked thru cape manager? Then, most importantly, if I did read and write through the /sys tree using the Invensense driver would it be faster than /dev/i2c? Help on sorting this out would be much appreciated. -- For more options, visit http://beagleboard.org/discuss --- You received this message because you are subscribed to the Google Groups "BeagleBoard" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/groups/opt_out.
