Difference between revisions of "JSX"
From MSX Game Library
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This protocol can manage joypads with up to 15 analog axis (one stick requires 2 axis) and 18 buttons. | This protocol can manage joypads with up to 15 analog axis (one stick requires 2 axis) and 18 buttons. | ||
| + | |||
| + | PSG register 15 (R#15) is use for MSX to device communication and R#14 for device to MSX communication. Data is sent to MSX 6 bits per 6 bits. | ||
| + | |||
| + | Pin binding for received data: | ||
| + | <pre> | ||
| + | 7 6 5 4 3 2 1 0 | ||
| + | –-–-–-–-–-–-–-–--–-–-–-–- | ||
| + | 0 0 P7 P6 P4 P3 P2 P1 | ||
| + | </pre> | ||
=== No-communication state === | === No-communication state === | ||
| Line 12: | Line 21: | ||
Read R#14 | Read R#14 | ||
| − | : Get 0x0F | + | : Get 0x0F (JSX fingerprint) |
: (or any value between 00-3F not already return by other MSX devices) | : (or any value between 00-3F not already return by other MSX devices) | ||
| Line 26: | Line 35: | ||
Read R#14 | Read R#14 | ||
| − | : Get ID | + | : Get JSX device ID |
<pre> | <pre> | ||
7 6 5 4 3 2 1 0 | 7 6 5 4 3 2 1 0 | ||
| Line 59: | Line 68: | ||
* Next and last reading button states (for up to 6 boutons). | * Next and last reading button states (for up to 6 boutons). | ||
| − | Note: [https://www.msx.org/wiki/MSX-HID MSX-HID] | + | Note: [https://www.msx.org/wiki/MSX-HID MSX-HID] fingerprint would be: 0Fh, 09h, 0Fh |
[[File:Joystick.png|512px]] | [[File:Joystick.png|512px]] | ||
[[Category:Proposal]][[Category:Proposal/Protocol]] | [[Category:Proposal]][[Category:Proposal/Protocol]] | ||
Revision as of 00:16, 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.
PSG register 15 (R#15) is use for MSX to device communication and R#14 for device to MSX communication. Data is sent to MSX 6 bits per 6 bits.
Pin binding for received data:
7 6 5 4 3 2 1 0 –-–-–-–-–-–-–-–--–-–-–-–- 0 0 P7 P6 P4 P3 P2 P1
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, 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 2 axis (a stick with X and Y axis), and up to 6 buttons, 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
