Investigating sensors support in a tablet

Transcription

1 Investigating sensors support in a tablet Fabien lysias Goncalves December 9, 2014

2 Introduction Did not know exactly what to work on Asked gaby There, this doesn t work

3 Section 1 The LSM303DLH

4 Where to start? How does it work? Using an accelerometer

5 Where to start? Which accelerometer? From Archlinux s wiki: The Series 7 Slate, as far as I can tell uses a STMicroelectronics LSM303DLH I am currently trying to get that up and running. Once I do, I ll post instructions on the LSM303DLH page

6 Where to start? Which accelerometer? From Archlinux s wiki: The Series 7 Slate, as far as I can tell uses a STMicroelectronics LSM303DLH I am currently trying to get that up and running. Once I do, I ll post instructions on the LSM303DLH page This page was last modified on 13 June 2012, at 15:54

7 Where to start? Generalities about the device STMicroelectronics 3D acceleration sensor 3D magnetic sensor Deprecated Communicates using I 2 C

8 Where to start? People trying to write a driver December 2010 [email protected]

9 Where to start? People trying to write a driver December 2010 [email protected] September 2012 [email protected]

10 Where to start? People trying to write a driver December 2010 [email protected] September 2012 [email protected] Ok, why not do it myself?

11 The device I 2 C multi-master, multi-slave serial bus 2 bidirectionnal lines, one data (SDA) and one clock (SCL) 7-bit address (in our case)

12 The device I 2 C communication example

13 The device st accel const s t r u c t o f d e v i c e i d s t a c c e l o f m a t c h [ ] = { {. c o m p a t i b l e = st, lsm303dlh a c c e l,. data = LSM303DLH ACCEL DEV NAME, }, [... ]

14 The device st accel const s t r u c t o f d e v i c e i d s t a c c e l o f m a t c h [ ] = { {. c o m p a t i b l e = st, lsm303dlh a c c e l,. data = LSM303DLH ACCEL DEV NAME, }, [... ] In Kconfig: c o n f i g IIO ST ACCEL 3AXIS t r i s t a t e S T M i c r o e l e c t r o n i c s a c c e l e r o m e t e r s 3 A x i s D r i v e r

15 The device st accel - side note Some adapters understand only the SMBus (System Management Bus) protocol, which is a subset from the I2C protocol. st sensors module

16 Section 2 The magnetometer

17 What is it? Principle Vector with force/direction

18 Communicating with the device flag{4ll0} How are devices handled? s t r u c t i 2 c d r i v e r { [... ] i n t ( probe ) ( s t r u c t i 2 c c l i e n t, c o n s t s t r u c t i 2 c d e v i c e i d ) ; [... ] } Driver returns 0 if it wants to handle the device.

19 Communicating with the device How are devices handled? The probe function is called when an entry in the id table name field matches the device s name. s t a t i c const s t r u c t i 2 c d e v i c e i d s t a c c e l i d t a b l e [ ] = { { LSM303DLH ACCEL DEV NAME }, // l s m d l h a c c e l [... ] }

20 Section 3 Do we have the right device?

21 Windows and Android What Windows says Not much!

22 Windows and Android What Windows says OK. What about Android?

23 Windows and Android What Android says u0 : / $ lsmod grep a c c e l h i d s e n s o r a c c e l 3 d [... ]

24 Windows and Android HID sensor? HID? drivers/iio/accel IIO?

25 Windows and Android HID sensor? HID? drivers/iio/accel IIO? IIO is not included in the kernel shipped with archlinux

26 Windows and Android Let s try in archlinux hid-sensor-hub registers as a HID driver dispatches to other spectific drivers $ dmesg g r e p p r o b i n g p r o b i n g ; name : HID SENSOR // i n hid s e n s o r a c c e l 3d. c p r o b i n g r e t u r n e d 0 // i n hid s e n s o r a c c e l 3d. c

27 Windows and Android What s left? $ dmesg grep vendor vendor i d : 1155 // i n hid s e n s o r hub. c From HID: 1155 STMicroelectronics $ dmesg grep p r o d u c t p r o d u c t i d : // i n hid s e n s o r hub. c Product IDs (PIDs) are assigned by each vendor as they see fit

28 Windows and Android What s left? $ dmesg grep vendor vendor i d : 1155 // i n hid s e n s o r hub. c From HID: 1155 STMicroelectronics $ dmesg grep p r o d u c t p r o d u c t i d : // i n hid s e n s o r hub. c Product IDs (PIDs) are assigned by each vendor as they see fit Enable device in /sys/bus/iio/devices/iio:devicex Read /dev/iio:devicex

29 Windows and Android Conclusion Questions?