Subversion Repositories or1k_soc_on_altera_embedded_dev_kit

** Introduction

This document describes what I managed to discover about the protocol used to

specify force effects to I-Force 2.0 devices.  None of this information comes

from Immerse. That's why you should not trust what is written in this

document. This document is intended to help understanding the protocol.

This is not a reference. Comments and corrections are welcome.  To contact me,

send an email to: johann.deneux@gmail.com

** WARNING **

I shall not be held responsible for any damage or harm caused if you try to

send data to your I-Force device based on what you read in this document.

** Preliminary Notes:

All values are hexadecimal with big-endian encoding (msb on the left). Beware,

values inside packets are encoded using little-endian.  Bytes whose roles are

unknown are marked ???  Information that needs deeper inspection is marked (?)

** General form of a packet **

This is how packets look when the device uses the rs232 to communicate.

2B OP LEN DATA CS

CS is the checksum. It is equal to the exclusive or of all bytes.

When using USB:

OP DATA

The 2B, LEN and CS fields have disappeared, probably because USB handles frames and

data corruption is handled or unsignificant.

First, I describe effects that are sent by the device to the computer

** Device input state

This packet is used to indicate the state of each button and the value of each

axis

OP= 01 for a joystick, 03 for a wheel

LEN= Varies from device to device

00 X-Axis lsb

01 X-Axis msb

02 Y-Axis lsb, or gas pedal for a wheel

03 Y-Axis msb, or brake pedal for a wheel

04 Throttle

05 Buttons

06 Lower 4 bits: Buttons

   Upper 4 bits: Hat

07 Rudder

** Device effects states

OP= 02

LEN= Varies

00 ? Bit 1 (Value 2) is the value of the deadman switch

01 Bit 8 is set if the effect is playing. Bits 0 to 7 are the effect id.

02 ??

03 Address of parameter block changed (lsb)

04 Address of parameter block changed (msb)

05 Address of second parameter block changed (lsb)

... depending on the number of parameter blocks updated

** Force effect **

OP=  01

LEN= 0e

00 Channel (when playing several effects at the same time, each must be assigned a channel)

01 Wave form

        Val 00 Constant

        Val 20 Square

        Val 21 Triangle

        Val 22 Sine

        Val 23 Sawtooth up

        Val 24 Sawtooth down

        Val 40 Spring (Force = f(pos))

        Val 41 Friction (Force = f(velocity)) and Inertia (Force = f(acceleration))

02 Axes affected and trigger

        Bits 4-7: Val 2 = effect along one axis. Byte 05 indicates direction

                  Val 4 = X axis only. Byte 05 must contain 5a

                  Val 8 = Y axis only. Byte 05 must contain b4

                  Val c = X and Y axes. Bytes 05 must contain 60

        Bits 0-3: Val 0 = No trigger

                  Val x+1 = Button x triggers the effect

        When the whole byte is 0, cancel the previously set trigger

03-04 Duration of effect (little endian encoding, in ms)

05 Direction of effect, if applicable. Else, see 02 for value to assign.

06-07 Minimum time between triggering.

08-09 Address of periodicity or magnitude parameters

0a-0b Address of attack and fade parameters, or ffff if none.

*or*

08-09 Address of interactive parameters for X-axis, or ffff if not applicable

0a-0b Address of interactive parameters for Y-axis, or ffff if not applicable

0c-0d Delay before execution of effect (little endian encoding, in ms)

** Time based parameters **

*** Attack and fade ***

OP=  02

LEN= 08

00-01 Address where to store the parameteres

02-03 Duration of attack (little endian encoding, in ms)

04 Level at end of attack. Signed byte.

05-06 Duration of fade.

07 Level at end of fade.

*** Magnitude ***

OP=  03

LEN= 03

00-01 Address

02 Level. Signed byte.

*** Periodicity ***

OP=  04

LEN= 07

00-01 Address

02 Magnitude. Signed byte.

03 Offset. Signed byte.

04 Phase. Val 00 = 0 deg, Val 40 = 90 degs.

05-06 Period (little endian encoding, in ms)

** Interactive parameters **

OP=  05

LEN= 0a

00-01 Address

02 Positive Coeff

03 Negative Coeff

04+05 Offset (center)

06+07 Dead band (Val 01F4 = 5000 (decimal))

08 Positive saturation (Val 0a = 1000 (decimal) Val 64 = 10000 (decimal))

09 Negative saturation

The encoding is a bit funny here: For coeffs, these are signed values. The

maximum value is 64 (100 decimal), the min is 9c.

For the offset, the minimum value is FE0C, the maximum value is 01F4.

For the deadband, the minimum value is 0, the max is 03E8.

** Controls **

OP=  41

LEN= 03

00 Channel

01 Start/Stop

        Val 00: Stop

        Val 01: Start and play once.

        Val 41: Start and play n times (See byte 02 below)

02 Number of iterations n.

** Init **

*** Querying features ***

OP=  ff

Query command. Length varies according to the query type.

The general format of this packet is:

ff 01 QUERY [INDEX] CHECKSUM

responses are of the same form:

FF LEN QUERY VALUE_QUERIED CHECKSUM2

where LEN = 1 + length(VALUE_QUERIED)

**** Query ram size ****

QUERY = 42 ('B'uffer size)

The device should reply with the same packet plus two additional bytes

containing the size of the memory:

ff 03 42 03 e8 CS would mean that the device has 1000 bytes of ram available.

**** Query number of effects ****

QUERY = 4e ('N'umber of effects)

The device should respond by sending the number of effects that can be played

at the same time (one byte)

ff 02 4e 14 CS would stand for 20 effects.

**** Vendor's id ****

QUERY = 4d ('M'anufacturer)

Query the vendors'id (2 bytes)

**** Product id *****

QUERY = 50 ('P'roduct)

Query the product id (2 bytes)

**** Open device ****

QUERY = 4f ('O'pen)

No data returned.

**** Close device *****

QUERY = 43 ('C')lose

No data returned.

**** Query effect ****

QUERY = 45 ('E')

Send effect type.

Returns nonzero if supported (2 bytes)

**** Firmware Version ****

QUERY = 56 ('V'ersion)

Sends back 3 bytes - major, minor, subminor

*** Initialisation of the device ***

**** Set Control ****

!!! Device dependent, can be different on different models !!!

OP=  40   []

LEN= 2 or 3

00 Idx

   Idx 00 Set dead zone (0..2048)

   Idx 01 Ignore Deadman sensor (0..1)

   Idx 02 Enable comm watchdog (0..1)

   Idx 03 Set the strength of the spring (0..100)

   Idx 04 Enable or disable the spring (0/1)

   Idx 05 Set axis saturation threshold (0..2048)

**** Set Effect State ****

OP=  42 

LEN= 1

00 State

   Bit 3 Pause force feedback

   Bit 2 Enable force feedback

   Bit 0 Stop all effects

**** Set overall gain ****

OP=  43 

LEN= 1

00 Gain

   Val 00 = 0%

   Val 40 = 50%

   Val 80 = 100%

** Parameter memory **

Each device has a certain amount of memory to store parameters of effects.

The amount of RAM may vary, I encountered values from 200 to 1000 bytes. Below

is the amount of memory apparently needed for every set of parameters:

 - period : 0c

 - magnitude : 02

 - attack and fade : 0e

 - interactive : 08

** Appendix: How to study the protocol ? **

1. Generate effects using the force editor provided with the DirectX SDK, or

use Immersion Studio (freely available at their web site in the developer section:

www.immersion.com)

2. Start a soft spying RS232 or USB (depending on where you connected your

joystick/wheel). I used ComPortSpy from fCoder (alpha version!)

3. Play the effect, and watch what happens on the spy screen.

A few words about ComPortSpy:

At first glance, this software seems, hum, well... buggy. In fact, data appear with a

few seconds latency. Personally, I restart it every time I play an effect.

Remember it's free (as in free beer) and alpha!

** URLS **

Check www.immerse.com for Immersion Studio, and www.fcoder.com for ComPortSpy.

** Author of this document **

Johann Deneux 

Home page at http://www.esil.univ-mrs.fr/~jdeneux/projects/ff/

Additions by Vojtech Pavlik.

I-Force is trademark of Immersion Corp.