The wiimote motion plus gyros use two scales to report fast and slow
rotation - below 440 deg/s uses 8192/440 units / deg/s, and above uses
8192/2000 units / deg/s.
Previously this driver attempted to linearize the two by scaling the fast
rate by 18 and the slow by 9, but this results in a scale of
8192*9/440 = ~167.564 for slow and 8192*18/2000 = 73.728 for fast.
Correct the fast motion scale factor so that both report ~167.564
units / deg/s
Signed-off-by: Cyan Ogilvie <[email protected]>
---
drivers/hid/hid-wiimote-modules.c | 14 ++++++++------
1 file changed, 8 insertions(+), 6 deletions(-)
diff --git a/drivers/hid/hid-wiimote-modules.c b/drivers/hid/hid-wiimote-modules.c
index 4390eee..c830ed3 100644
--- a/drivers/hid/hid-wiimote-modules.c
+++ b/drivers/hid/hid-wiimote-modules.c
@@ -2049,9 +2049,11 @@ static void wiimod_mp_in_mp(struct wiimote_data *wdata, const __u8 *ext)
* -----+------------------------------+-----+-----+
* The single bits Yaw, Roll, Pitch in the lower right corner specify
* whether the wiimote is rotating fast (0) or slow (1). Speed for slow
- * roation is 440 deg/s and for fast rotation 2000 deg/s. To get a
- * linear scale we multiply by 2000/440 = ~4.5454 which is 18 for fast
- * and 9 for slow.
+ * roation is 8192/440 units / deg/s and for fast rotation 8192/2000
+ * units / deg/s. To get a linear scale for fast rotation we multiply
+ * by 2000/440 = ~4.5454 and scale both fast and slow by 9 to match the
+ * previous scale reported by this driver.
+ * This leaves a linear scale with 8192*9/440 (~167.564) units / deg/s.
* If the wiimote is not rotating the sensor reports 2^13 = 8192.
* Ext specifies whether an extension is connected to the motionp.
* which is parsed by wiimote-core.
@@ -2070,15 +2072,15 @@ static void wiimod_mp_in_mp(struct wiimote_data *wdata, const __u8 *ext)
z -= 8192;
if (!(ext[3] & 0x02))
- x *= 18;
+ x = (x * 2000 * 9) / 440;
else
x *= 9;
if (!(ext[4] & 0x02))
- y *= 18;
+ y = (y * 2000 * 9) / 440;
else
y *= 9;
if (!(ext[3] & 0x01))
- z *= 18;
+ z = (z * 2000 * 9) / 440;
else
z *= 9;
--
2.1.4
Hi
On Wed, Mar 16, 2016 at 5:59 PM, Cyan Ogilvie <[email protected]> wrote:
> The wiimote motion plus gyros use two scales to report fast and slow
> rotation - below 440 deg/s uses 8192/440 units / deg/s, and above uses
> 8192/2000 units / deg/s.
>
> Previously this driver attempted to linearize the two by scaling the fast
> rate by 18 and the slow by 9, but this results in a scale of
> 8192*9/440 = ~167.564 for slow and 8192*18/2000 = 73.728 for fast.
>
> Correct the fast motion scale factor so that both report ~167.564
> units / deg/s
>
> Signed-off-by: Cyan Ogilvie <[email protected]>
> ---
> drivers/hid/hid-wiimote-modules.c | 14 ++++++++------
> 1 file changed, 8 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/hid/hid-wiimote-modules.c b/drivers/hid/hid-wiimote-modules.c
> index 4390eee..c830ed3 100644
> --- a/drivers/hid/hid-wiimote-modules.c
> +++ b/drivers/hid/hid-wiimote-modules.c
> @@ -2049,9 +2049,11 @@ static void wiimod_mp_in_mp(struct wiimote_data *wdata, const __u8 *ext)
> * -----+------------------------------+-----+-----+
> * The single bits Yaw, Roll, Pitch in the lower right corner specify
> * whether the wiimote is rotating fast (0) or slow (1). Speed for slow
> - * roation is 440 deg/s and for fast rotation 2000 deg/s. To get a
> - * linear scale we multiply by 2000/440 = ~4.5454 which is 18 for fast
> - * and 9 for slow.
Oh dear! My initial reasoning was completely off. I somehow upscaled
4.5 to 18, and 1 to 9, when it should have been 1 to 4. Oops!
> + * roation is 8192/440 units / deg/s and for fast rotation 8192/2000
> + * units / deg/s. To get a linear scale for fast rotation we multiply
> + * by 2000/440 = ~4.5454 and scale both fast and slow by 9 to match the
> + * previous scale reported by this driver.
> + * This leaves a linear scale with 8192*9/440 (~167.564) units / deg/s.
> * If the wiimote is not rotating the sensor reports 2^13 = 8192.
> * Ext specifies whether an extension is connected to the motionp.
> * which is parsed by wiimote-core.
> @@ -2070,15 +2072,15 @@ static void wiimod_mp_in_mp(struct wiimote_data *wdata, const __u8 *ext)
> z -= 8192;
>
> if (!(ext[3] & 0x02))
> - x *= 18;
> + x = (x * 2000 * 9) / 440;
> else
> x *= 9;
> if (!(ext[4] & 0x02))
> - y *= 18;
> + y = (y * 2000 * 9) / 440;
> else
> y *= 9;
> if (!(ext[3] & 0x01))
> - z *= 18;
> + z = (z * 2000 * 9) / 440;
So 2000/440 ~= 4.5, so this is exactly what the initial comment said.
Patch looks good to me:
Reviewed-by: David Herrmann <[email protected]>
Thanks
David
> else
> z *= 9;
>
> --
> 2.1.4
>
On Thu, 17 Mar 2016, David Herrmann wrote:
> > @@ -2070,15 +2072,15 @@ static void wiimod_mp_in_mp(struct wiimote_data *wdata, const __u8 *ext)
> > z -= 8192;
> >
> > if (!(ext[3] & 0x02))
> > - x *= 18;
> > + x = (x * 2000 * 9) / 440;
> > else
> > x *= 9;
> > if (!(ext[4] & 0x02))
> > - y *= 18;
> > + y = (y * 2000 * 9) / 440;
> > else
> > y *= 9;
> > if (!(ext[3] & 0x01))
> > - z *= 18;
> > + z = (z * 2000 * 9) / 440;
>
> So 2000/440 ~= 4.5, so this is exactly what the initial comment said.
> Patch looks good to me:
>
> Reviewed-by: David Herrmann <[email protected]>
Appplied to for-4.6/upstream-fixes. Thanks,
--
Jiri Kosina
SUSE Labs