[WIP] [RFC]: OpenHaptics protocol

[leon0399]

Here I am just writing ideas from my mind to future implement in our own protocol, when current protocol from bHaptics when it ceases to meet the needs

OpenHaptics Protocol

Coordinates encoding

Each axis (X and Y) is _uint8_t_ between 0 and 255

Coordinates preview

``` (0, 0) (128, 0) (255, 0) (0, 128) (128, 128) (255, 128) (0, 255) (128, 255) (255, 255) ```

Intensity

Intensity is _uint8_t_:

0: 0%, 255: 100%

Effects layer

Effect layer is 16 possible values (4 bits - _uint8_t << 4_)

Proposed Effects layer IDs (WIP)

* Vibro: `0x0` * Touch (LRA): `0x1` * Temperature (Peltier): `0x2` * Electricity (TENS): `0x3`

Body Parts IDs mapping

Every diverging part of the body is separated into Front and Back faces. Coordinate path has 255 possible values (8 bits - _uint8_t_)

Proposed Body Parts IDs (WIP)

* `human://chest`: * `human://chest/front`: `0x00` * `human://chest/back`: `0x01` * `human://arm`: * `human://arm/left`: `0x02` * `human://arm/right`: `0x03` * `human://forearm`: * `human://forearm/left`: `0x04` * `human://forearm/right`: `0x05` * `human://hand`: * `human://hand/left`: * `human://hand/left/palm`: * `human://hand/left/palm/front`: `0x06` * `human://hand/left/palm/back`: `0x07` * `human://hand/left/finger`: * `human://hand/left/finger/thumb`: `0x08` * `human://hand/left/finger/index`: `0x09` * `human://hand/left/finger/middle`: `0x0a` * `human://hand/left/finger/ring`: `0x0b` * `human://hand/left/finger/pinky`: `0x0c` * `human://hand/right`: * `human://hand/right/palm`: * `human://hand/right/palm/front`: `0x0d` * `human://hand/right/palm/back`: `0x0e` * `human://hand/right/finger`: * `human://hand/right/finger/thumb`: `0x0f` * `human://hand/right/finger/index`: `0x10` * `human://hand/right/finger/middle`: `0x11` * `human://hand/right/finger/ring`: `0x12` * `human://hand/right/finger/pinky`: `0x13` * `human://upper_leg`: * `human://upper_leg/left`: `0x14` * `human://upper_leg/right`: `0x15` * `human://lower_leg`: * `human://lower_leg/left`: `0x16` * `human://lower_leg/right`: `0x17` * `human://foot`: * `human://foot/left`: * `human://foot/left/top`: `0x18` * `human://foot/left/bottom`: `0x19` * `human://foot/right`: * `human://foot/right/top`: `0x1a` * `human://foot/right/bottom`: `0x1b` * `human://neck`: `0x1c` * `human://head`: * `human://head/face`: `0x1d` * `human://head/back`: `0x1e` * `human://head/top`: `0x1f`

[leon0399]

After some thought, I've decided on the given packet structure:

• Layer: 4 bits
• Reserved: 4 bits
• Body part path: 8 bits
• Length of the motors values array: 8 bits
• Array of motors values:
  • Motor coordinate: 16 bits (8 + 8 per X + Y)
  • Motor intensity: 8 bits

Thus:

• Preamble is 24 bits (3 bytes)
• Single motor value is 24 bits (3 bytes)

Transition limits

• With minimal 23 bytes MTU, single transmission is (23 - 3 (preamble)) / 3 (single motor) = 6 motors
• With default automatic iOS MTU change to 185 bytes is (185 - 3 (preamble)) / 3 (single motor) = 60 motors

Future software can automatically adjust MTU for each device in order to handle every motor change in a single packet (e.g. 20 motors per body part on x40 vest), so MTU for x40 vest might be 3*20 + 3 = 63 bytes