| 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 |