Difference between revisions of "JSX"
From MSX Game Library
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</pre> | </pre> | ||
| + | == States == | ||
=== No-communication state === | === No-communication state === | ||
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=== Read bytes === | === Read bytes === | ||
| − | Repeat this step for each axis, then for each button row. | + | Repeat this step for each axis (if any), then for each button row. |
Write R#15 | Write R#15 | ||
| Line 61: | Line 62: | ||
== Example == | == Example == | ||
| − | For a Joypad with | + | For a Joypad with a stick with X and Y axis (2 axis), and 4 buttons (1 row), the reading process would be: |
| − | |||
* After starting communication, first read to R#14 return the ID.<br/>ID: 0x09 [00 0010 01] for 2 axis, and 1 buttons row, | * After starting communication, first read to R#14 return the ID.<br/>ID: 0x09 [00 0010 01] for 2 axis, and 1 buttons row, | ||
* Next reading give X-axis value [-32 ; 31], | * Next reading give X-axis value [-32 ; 31], | ||
* Next reading give Y-axis value [-32 ; 31], | * Next reading give Y-axis value [-32 ; 31], | ||
* Next and last reading button states (for up to 6 boutons). | * Next and last reading button states (for up to 6 boutons). | ||
| − | + | [[File:Joystick.png|512px]] | |
Note: [https://www.msx.org/wiki/MSX-HID MSX-HID] fingerprint would be: 0Fh, 09h, 0Fh | Note: [https://www.msx.org/wiki/MSX-HID MSX-HID] fingerprint would be: 0Fh, 09h, 0Fh | ||
| − | |||
| − | |||
[[Category:Proposal]][[Category:Proposal/Protocol]] | [[Category:Proposal]][[Category:Proposal/Protocol]] | ||
Revision as of 00:27, 20 October 2024
Contents
Protocol
Proposal for a protocol to handle a joypad with a variable number of sticks and buttons, plug in the MSX’s general purpose port.
This protocol can manage joypads with up to 15 analog axis (one stick requires 2 axis) and 18 buttons.
A pulse on Pin 8 is used to start communication while, consecutive pulse on Pin 6 is used to synchronize data transmission (6 bits per 6 bits).
Pin binding for received data:
Bits 7 6 5 4 3 2 1 0 –-–-–-–-–-–-–-–--–-–- Pins x x 7 6 4 3 2 1
States
No-communication state
Write R#15
- Pin 8: LOW
- Pin 6: any value
Read R#14
- Get 0x0F (JSX fingerprint)
- (or any value between 00-3F not already return by other MSX devices)
Start communication and get ID
Write R#15
- Pin 8: LOW (in case Pin 8 have been modified by another device)
- Pin 6: any value
Write R#15
- Pin 8: HIGH (start communication)
- Pin 6: HIGH
Read R#14
- Get JSX device ID
7 6 5 4 3 2 1 0
–-–-–-–-–-–-–-–--
x x A A A A B B
│ │ │ │ └─┴── Number of button rows (0-3)
└─┴─┴─┴────── Number of axis (0-15)
Read bytes
Repeat this step for each axis (if any), then for each button row.
Write R#15
- Pin 8: HIGH
- Pin 6: LOW
Write R#15
- Pin 8: HIGH
- Pin 6: HIGH
Read R#14
- Get 6-bits values
- For axis: signed 6-bits value [-32 ; 31]
- For boutons: bits field for 6 boutons (0: pressed, 1: released)
Example
For a Joypad with a stick with X and Y axis (2 axis), and 4 buttons (1 row), the reading process would be:
- After starting communication, first read to R#14 return the ID.
ID: 0x09 [00 0010 01] for 2 axis, and 1 buttons row, - Next reading give X-axis value [-32 ; 31],
- Next reading give Y-axis value [-32 ; 31],
- Next and last reading button states (for up to 6 boutons).
Note: MSX-HID fingerprint would be: 0Fh, 09h, 0Fh