JSX-B - Revision history

Aoineko: /* Protocol */

2024-10-31T12:35:13Z

‎Protocol

Aoineko at 12:32, 31 October 2024

2024-10-31T12:32:22Z

Aoineko at 12:30, 31 October 2024

2024-10-31T12:30:50Z

Aoineko: /* Device ID */

2024-10-31T12:29:20Z

‎Device ID

Aoineko at 12:14, 31 October 2024

2024-10-31T12:14:51Z

Aoineko: /* States */

2024-10-31T12:13:46Z

‎States

Aoineko at 12:09, 31 October 2024

2024-10-31T12:09:29Z

Aoineko: Created page with "== Protocol == Proposal for a protocol to handle joypads with a variable number of sticks and buttons, plug in the MSX’s [https://www.msx.org/wiki/General_Purpose_port gene..."

2024-10-31T12:08:57Z

Created page with "== Protocol == Proposal for a protocol to handle joypads with a variable number of sticks and buttons, plug in the MSX’s [https://www.msx.org/wiki/General_Purpose_port gene..."

New page

== Protocol ==

Proposal for a protocol to handle joypads with a variable number of sticks and buttons, plug in the MSX’s [https://www.msx.org/wiki/General_Purpose_port general purpose port].

This protocol can manage joypads with up to 15 analog axis (one stick requires 2 axis) and 18 buttons.

Pin 8 is used to synchronize data transmission:
* Leaving Pin 8 LOW for long enough (>1 ms, about 3580 t-states) resets the joystick's internal counter,
* then successive pulses on Pin 8 (LOW > HIGH) are used for data transmission (6 bits per 6 bits).

Pin 6 and 7 are used as 2-bit transfer mode identifier:
* 00: Get Device ID
* 01: Serial read of joypad input data data (and increment internal counter)
* 10: ''Reserved''
* 11: ''Reserved''

Pin binding for received data:
<pre>
Bits 7 6 5 4 3 2 1 0
–-–-–-–-–-–-–-–--–-–-
Pins x x 7 6 4 3 2 1
</pre>

== States ==
=== No-communication state ===

Write R#15
: Pin 8: LOW
: Pin 6: ''any value''

Read R#14
: Get 0x0F (JSX idle fingerprint)
: Note: It could be any value between 00-3F not already return by [https://www.msx.org/wiki/MSX-HID#List_of_known_fingerprints 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
<pre>
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)
</pre>
:Note: Number of axis or number of button rows can be zero, but not both. So any device ID up to 0x3F is valid except 0x00.

=== Read bytes ===
Repeat this step for each axis (if any), then for each button row (if any). Number of axis and button rows is given by the device ID

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 give 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

[[Category:Proposal]][[Category:Proposal/Protocol]]

@@ Line 10: / Line 10: @@
 Pin 6 and 7 are used as 2-bit transfer mode identifier:
-* <tt>00</tt>: Get Device ID
+* <tt>00</tt>: ''Reserved''
-* <tt>01</tt>: Serial read of joypad input data (and increment internal counter)
+* <tt>01</tt>: ''Reserved''
-* <tt>10</tt>: ''Reserved''
+* <tt>10</tt>: Get Device ID
-* <tt>11</tt>: ''Reserved''
+* <tt>11</tt>: Serial read of joypad input data (and increment internal counter)
 Pin binding for received data:

@@ Line 11: / Line 11: @@
 Pin 6 and 7 are used as 2-bit transfer mode identifier:
 * <tt>00</tt>: Get Device ID
-* <tt>01</tt>: Serial read of joypad input data data (and increment internal counter)
+* <tt>01</tt>: Serial read of joypad input data (and increment internal counter)
 * <tt>10</tt>: ''Reserved''
 * <tt>11</tt>: ''Reserved''
@@ Line 37: / Line 37: @@
 Write R#15
-: Pin 6: LOW
+: Pin 6: ''any value''
-: Pin 7: LOW
+: Pin 7: ''any value''
 : Pin 8: LOW (for >1 ms)
@@ Line 61: / Line 61: @@
 Write R#15
-: Pin 8: HIGH
+: Pin 6: ''any value''
-: Pin 6: LOW
+: Pin 7: ''any value''
 Write R#15
 : Pin 8: HIGH
 Read R#14

@@ Line 1: / Line 1: @@
 == Protocol ==
-Proposal for a protocol to handle joypads with a variable number of sticks and buttons, plug in the MSX’s [https://www.msx.org/wiki/General_Purpose_port general purpose port].
+Proposal for a protocol to handle joypads with a '''variable number of sticks and buttons''', plug in the MSX’s '''[https://www.msx.org/wiki/General_Purpose_port general purpose port]'''.
-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'''.
 Pin 8 is used to synchronize data transmission: