1 ===========================
2 Walkera WK-0701 transmitter
3 ===========================
4
5 Walkera WK-0701 transmitter is supplied with a
6 helicopters such as HM36, HM37, HM60. The walk
7 this transmitter as joystick
8
9 Devel homepage and download:
10 http://zub.fei.tuke.sk/walkera-wk0701/
11
12 or use cogito:
13 cg-clone http://zub.fei.tuke.sk/GIT/walkera070
14
15
16 Connecting to PC
17 ================
18
19 At back side of transmitter S-video connector
20 pulses from processor to HF part can be found
21 pin 3 is GND. Between pin 3 and CPU 5k6 resist
22 modulation pulses to PC, signal pulses must be
23
24 Cable: (walkera TX to parport)
25
26 Walkera WK-0701 TX S-VIDEO connector::
27
28 (back side of TX)
29 __ __ S-video:
30 / |_| \ pin 2 (signal)
31 / O 4 3 O \ pin 3 (GND) L
32 ( O 2 1 O )
33 \ ___ / 2 ________________________
34 | [___] |
35 ------- 3 ________________________
36
37
38 I use green LED and BC109 NPN transistor.
39
40 Software
41 ========
42
43 Build kernel with walkera0701 module. Module w
44 access to parport, modules like lp must be unl
45 walkera0701 module, check dmesg for error mess
46 cable and run jstest /dev/input/js0 to see val
47 be changed by TX "joystick", check output from
48 (usually irq7) parport must increase if TX is
49
50
51
52 Technical details
53 =================
54
55 Driver use interrupt from parport ACK input bi
56 using hrtimers.
57
58 Frame format:
59 Based on walkera WK-0701 PCM Format descriptio
60 (downloaded from http://www.smartpropoplus.com
61
62 Signal pulses
63 -------------
64
65 ::
66
67 (ANALOG)
68 SYNC BIN OCT
69 +---------+ +------+
70 | | | |
71 --+ +------+ +---
72
73 Frame
74 -----
75
76 ::
77
78 SYNC , BIN1, OCT1, BIN2, OCT2 ... BIN24, OCT2
79
80 pulse length
81 ------------
82
83 ::
84
85 Binary values: Analog octal v
86
87 288 uS Binary 0 318 uS 0
88 438 uS Binary 1 398 uS 0
89 478 uS 0
90 558 uS 0
91 638 uS 1
92 1306 uS SYNC 718 uS 1
93 798 uS 1
94 878 uS 1
95
96 24 bin+oct values + 1 bin value = 24*4+1 bits
97
98 (Warning, pulses on ACK are inverted by transi
99 to bin change or octal value to bin change).
100
101 Binary data representations
102 ---------------------------
103
104 One binary and octal value can be grouped to n
105 values can be sampled between sync pulses.
106
107 Values for first four channels (analog joystic
108 first 10 nibbles. Analog value is represented
109 absolute binary value. (10 bits per channel).
110 first ten nibbles.
111
112 Next nibbles 12 .. 21 represents four channels
113 directly controlled from TX). Binary represent
114 four channels. In nibbles 22 and 23 is a speci
115 checksum for nibbles 12..23.
116
117 After last octal value for nibble 24 and next
118 binary value can be sampled. This bit and magi
119 software driver. Some details about this magic
120 Walkera_Wk-0701_PCM.pdf.
121
122 Checksum calculation
123 --------------------
124
125 Summary of octal values in nibbles must be sam
126 nibble (only first 3 bits are used). Binary va
127 calculated by sum of binary values in checked
128 in checked nibbles divided by 8. Only bit 0 of
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