Accelerometer, Gyros and ADC's etc within the kernel.

From: Jonathan Cameron
Date: Tue May 20 2008 - 06:06:15 EST

This email is basically a request for opinions on how and where such sensors
should be integrated into the kernel.

To set the scene...

Increasing numbers of embedded devices are being supplied attached MEMS
devices ( imote2 etc). Along with more traditional sensors such
as ADC's not being used for hardware monitoring, these do not really seem to
fit with in an particular subsystem of the kernel. A previous discussion on
lkml in 2006 considered the accelerometers to be found within some laptop
hard drives, but I haven't been able to track down any more general discussions
of such non hardware monitoring sensors.

The obvious possibilities are:

* To place the various drivers within the spi / i2c etc subsystems as relevant.

* To place within the hwmon subsystem as this is probably closest.
(there is already at least one straight ADC driver in hwmon)

* To create a new subsystem, or perhaps merely sysfs class to contain these

Typical requirements within an application include simply polling for current
readings, and using device triggered interrupts to grab data continuously to a
ring buffer, for collection by suitable userspace code. Obviously it would be
desirable to standardize sysfs controls for various calibration parameters as
much as possible across the various devices.

Any other suggestions welcome!

To illustrate the sort of devices here are a few I have drivers written for or will
shortly be writing (some submitted to hwmon and spi mailing lists, some not
finished as of yet)

ST Micro LIS3L02DQ 3D accelerometer. SPI device, no buffering, interrupt pin
raised high on new data being available. Currently the driver assumes, if
interrupts are enabled, that this is connected to a specified gpio.

VTI SCA3000 E05 3D accelerometer equiped with substantial ring buffer. SPI
device. Can operate either in buffered or direct mode. In buffered mode, interrupts
can be used to indicate when the ring buffer is 3/4 full triggering a download to
a larger ring buffer in the kernel if necessary.

Analog Devices ADIS16350 combined 3D accelerometer and gyro unit. SPI device.

Maxim MAX1363, MAX1238 ADC's. I2C devices. Some SPI ADC's ( for

Would be nice if practical to allow the framework to include RS232 devices such
as those from, and others.

Jonathan Cameron

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at
Please read the FAQ at