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f12652df PH |
1 | #ifndef __MM_DECODE_H |
2 | #define __MM_DECODE_H | |
3 | ||
4 | /* | |
5 | * Lookup trinary nibble | |
6 | * | |
7 | * This was implemented using a switch statement before. | |
8 | * Changing the lookup to a table did only add two bytes | |
9 | * of memory and saved ca. 50 bytes program memory. | |
10 | */ | |
11 | static const uint8_t __mm_nibble_table[16]={ | |
12 | [0x0] = 0, | |
13 | [0xc] = 1, | |
14 | [0x8] = 2, | |
15 | [0x3] = 3, | |
16 | [0xf] = 4, | |
17 | [0xb] = 5, | |
18 | [0x2] = 6, | |
19 | [0xe] = 7, | |
20 | [0xa] = 8 | |
21 | }; | |
22 | #define __mm_lookup_nibble(nibble) __mm_nibble_table[nibble & 0xf] | |
23 | ||
24 | static uint8_t __attribute__((unused)) mm_lookup_decoder(uint8_t mm_byte) | |
25 | { | |
26 | uint8_t low; | |
27 | uint8_t high; | |
28 | uint8_t retval; | |
29 | ||
30 | if (mm_byte == 0) | |
31 | return 80; | |
32 | low = __mm_lookup_nibble(mm_byte >> 4); | |
33 | high = __mm_lookup_nibble(mm_byte & 0xf); | |
34 | if (!low) | |
35 | return 0; | |
36 | ||
37 | /* retval = 9 * high + low; */ | |
38 | retval = high << 3; | |
39 | retval += high; | |
40 | retval += low; | |
41 | return retval; | |
42 | } | |
43 | ||
44 | static uint8_t __attribute__((unused)) mm_lookup_key(uint8_t mm_command) | |
45 | { | |
46 | uint8_t res; | |
47 | /* | |
48 | * Check for aabbccdd condition | |
49 | * | |
50 | * a a b b c c d d mm_command | |
51 | * XOR a b b c c d d 0 mm_command << 1 | |
52 | * Mask 1 0 1 0 1 0 1 0 0xaa | |
53 | * | |
54 | * Must be zero! | |
55 | * | |
56 | */ | |
57 | ||
58 | if ((mm_command ^ (mm_command << 1)) & 0xaa) | |
59 | return 0; | |
60 | /* | |
61 | * Protocol differences: | |
62 | * ===================== | |
63 | * | |
64 | * I have an old "central control" 6022 and a "control unit" 6021 | |
65 | * for measurements and test. It is assumed that the 6022 outputs | |
66 | * old MM1 format while the 6021 definitively outputs MM2 telegrams. | |
67 | * | |
68 | * In MM1, switch commands are different from MM2 with respect what | |
69 | * happens if you release a button. | |
70 | * | |
71 | * When you press a button, both protocols send | |
72 | * | |
73 | * <aaaaaaaa><00><aabbcc11> | |
74 | * | |
75 | * where a = 1, b = 2, c = 4 and the keys are numerated from 0 to 7 | |
76 | * in the order 1 red, 1 green, 2 red, 2 green and so on. | |
77 | * | |
78 | * The last two bits correspond to "on" state of the button/coil. | |
79 | * | |
80 | * When a key is released under MM1 protocol, the sequence sent is | |
81 | * analogue to the button down sequence: | |
82 | * | |
83 | * <aaaaaaaa><00><aabbcc00> where abc again represents the button's | |
84 | * address and the last bits now signal "off". | |
85 | * | |
86 | * MM2 handles this differently: | |
87 | * Whenever any key from the addressed decoder is released, the sequence | |
88 | * <aaaaaaaa>00<00000000> is sent - not only for key 0, but for all | |
89 | * keys! | |
90 | * | |
91 | * While MM1 presents the theoretical possibility to press several keys | |
92 | * independently and simultaneously (which my keyboard does NOT | |
93 | * support), MM2 supports only one key at a time (besides strange | |
94 | * sequences like "one down, another down, all up"... | |
95 | * | |
96 | * A decoder that strictly adheres to the MM1 standard would not work | |
97 | * properly with MM2 control units. As far as I know all K83/K84 | |
98 | * decoders always worked with MM2 control units. That means that | |
99 | * they reduce the commands to the possibilities of MM2 from the | |
100 | * beginning. | |
101 | * | |
102 | * Possible use cases for the old protocol button release commands: | |
103 | * - Determine if the protocol is MM1 or MM2 | |
104 | * - Implement hidden evil features into the controller which can | |
105 | * only be summoned by old MM1 gear or selfmade control telegram | |
106 | * generators. | |
107 | * | |
108 | * What this code now actually does: | |
109 | * ================================= | |
110 | * | |
111 | * When key pressed (aabbcc11), it will send out the key number in the | |
112 | * range 1-8 and 0 if it gets any key up command and therefore ignore | |
113 | * the key number if it is transmitted with the key up command. | |
114 | * | |
115 | */ | |
116 | if (!(mm_command & 0x01)) | |
117 | res = 0; | |
118 | else | |
119 | res = (mm_command & 0x80) * 1 + (mm_command & 0x20) * 0x02 | |
120 | + (mm_command & 0x08) * 0x04 + 1; | |
121 | return res; | |
122 | } | |
123 | ||
124 | #endif |