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1 | /* |
2 | * This file is part of the libsigrok project. | |
3 | * | |
4 | * Copyright (C) 2019 Gerhard Sittig <gerhard.sittig@gmx.net> | |
5 | * | |
6 | * This program is free software: you can redistribute it and/or modify | |
7 | * it under the terms of the GNU General Public License as published by | |
8 | * the Free Software Foundation, either version 3 of the License, or | |
9 | * (at your option) any later version. | |
10 | * | |
11 | * This program is distributed in the hope that it will be useful, | |
12 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
13 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
14 | * GNU General Public License for more details. | |
15 | * | |
16 | * You should have received a copy of the GNU General Public License | |
17 | * along with this program. If not, see <http://www.gnu.org/licenses/>. | |
18 | */ | |
19 | ||
20 | /* | |
21 | * This implements serial transport primitives for Victor DMM cables, | |
22 | * which forward normal DMM chips' protocols, but scramble the data in | |
23 | * the process of forwarding. Just undoing the cable's scrambling at | |
24 | * the serial communication level allows full re-use of existing DMM | |
25 | * drivers, instead of creating Victor DMM specific support code. | |
26 | * | |
27 | * The cable's scrambling is somewhat complex: | |
28 | * - The order of bits within the bytes gets reversed. | |
29 | * - The order of bytes within the packet gets shuffled (randomly). | |
30 | * - The byte values randomly get mapped to other values by adding a | |
31 | * sequence of magic values to packet's byte values. | |
32 | * None of this adds any value to the DMM chip vendor's protocol. It's | |
33 | * mere obfuscation and extra complexity for the receiving application. | |
34 | */ | |
35 | ||
36 | #include <config.h> | |
37 | #include <glib.h> | |
38 | #include <libsigrok/libsigrok.h> | |
39 | #include "libsigrok-internal.h" | |
40 | #include "serial_hid.h" | |
41 | #include <string.h> | |
42 | ||
43 | /** @cond PRIVATE */ | |
44 | #define LOG_PREFIX "serial-victor" | |
45 | /** @endcond */ | |
46 | ||
47 | #ifdef HAVE_SERIAL_COMM | |
48 | #ifdef HAVE_LIBHIDAPI | |
49 | ||
50 | /** | |
51 | * @file | |
52 | * | |
53 | * Support serial-over-HID, specifically the Victor 70/86 DMM cables. | |
54 | */ | |
55 | ||
56 | #define VICTOR_DMM_PACKET_LENGTH 14 | |
57 | ||
58 | static const struct vid_pid_item vid_pid_items_victor[] = { | |
59 | { 0x1244, 0xd237, }, | |
9451e01e | 60 | ALL_ZERO |
0cdb72c8 GS |
61 | }; |
62 | ||
0cdb72c8 GS |
63 | /* Reverse bits within a byte. */ |
64 | static uint8_t bit_reverse(uint8_t b) | |
65 | { | |
66 | static const uint8_t rev_nibble[] = { | |
67 | 0x00, 0x08, 0x04, 0x0c, 0x02, 0x0a, 0x06, 0x0e, | |
68 | 0x01, 0x09, 0x05, 0x0d, 0x03, 0x0b, 0x07, 0x0f, | |
69 | }; | |
70 | ||
71 | return (rev_nibble[(b >> 4) & 0xf]) | | |
72 | (rev_nibble[b & 0xf] << 4); | |
73 | } | |
74 | ||
75 | /* | |
76 | * The cable receives data by means of HID reports (simple data stream, | |
77 | * HID report encapsulation was already trimmed). Assume that received | |
78 | * data "is aligned", cope with zero or one 14-byte packets here, but | |
79 | * don't try to even bother with odd-length reception units. Also drop | |
80 | * the "all-zero" packets here which victor_dmm_receive_data() used to | |
81 | * eliminate at the device driver level in the past. | |
82 | */ | |
83 | static int victor_unobfuscate(uint8_t *rx_buf, size_t rx_len, | |
84 | uint8_t *ret_buf) | |
85 | { | |
86 | static const uint8_t obfuscation[VICTOR_DMM_PACKET_LENGTH] = { | |
87 | 'j', 'o', 'd', 'e', 'n', 'x', 'u', 'n', 'i', 'c', 'k', 'x', 'i', 'a', | |
88 | }; | |
89 | static const uint8_t shuffle[VICTOR_DMM_PACKET_LENGTH] = { | |
90 | 6, 13, 5, 11, 2, 7, 9, 8, 3, 10, 12, 0, 4, 1 | |
91 | }; | |
92 | ||
93 | GString *txt; | |
94 | int is_zero; | |
95 | size_t idx, to_idx; | |
96 | ||
97 | if (sr_log_loglevel_get() >= SR_LOG_SPEW) { | |
98 | txt = sr_hexdump_new(rx_buf, rx_len); | |
99 | sr_spew("Received %zu bytes: %s.", rx_len, txt->str); | |
100 | sr_hexdump_free(txt); | |
101 | } | |
102 | ||
103 | /* Pass unexpected data in verbatim form. */ | |
104 | if (rx_len != VICTOR_DMM_PACKET_LENGTH) { | |
105 | memcpy(ret_buf, rx_buf, rx_len); | |
106 | return rx_len; | |
107 | } | |
108 | ||
109 | /* Check for and discard all-zero packets. */ | |
110 | is_zero = 1; | |
111 | for (idx = 0; is_zero && idx < VICTOR_DMM_PACKET_LENGTH; idx++) { | |
112 | if (rx_buf[idx]) | |
113 | is_zero = 0; | |
114 | } | |
115 | if (is_zero) { | |
116 | sr_dbg("Received all zeroes packet, discarding."); | |
117 | return 0; | |
118 | } | |
119 | ||
120 | /* | |
121 | * Unobfuscate data bytes by subtracting a magic pattern, shuffle | |
122 | * the bits and bytes into the DMM chip's original order. | |
123 | */ | |
124 | for (idx = 0; idx < VICTOR_DMM_PACKET_LENGTH; idx++) { | |
125 | to_idx = VICTOR_DMM_PACKET_LENGTH - 1 - shuffle[idx]; | |
126 | ret_buf[to_idx] = bit_reverse(rx_buf[idx] - obfuscation[idx]); | |
127 | } | |
128 | ||
129 | if (sr_log_loglevel_get() >= SR_LOG_SPEW) { | |
130 | txt = sr_hexdump_new(ret_buf, idx); | |
131 | sr_spew("Deobfuscated: %s.", txt->str); | |
132 | sr_hexdump_free(txt); | |
133 | } | |
134 | ||
135 | return rx_len; | |
136 | } | |
137 | ||
138 | /* | |
139 | * Read into a local buffer, and unobfuscate into the caller's buffer. | |
140 | * Always receive full DMM packets. | |
141 | */ | |
142 | static int victor_read_bytes(struct sr_serial_dev_inst *serial, | |
143 | uint8_t *data, int space, unsigned int timeout) | |
144 | { | |
145 | uint8_t buf[VICTOR_DMM_PACKET_LENGTH]; | |
146 | int rc; | |
147 | ||
148 | if (space != sizeof(buf)) | |
149 | space = sizeof(buf); | |
150 | rc = ser_hid_hidapi_get_data(serial, 0, buf, space, timeout); | |
151 | if (rc == SR_ERR_TIMEOUT) | |
152 | return 0; | |
153 | if (rc < 0) | |
154 | return rc; | |
155 | if (rc == 0) | |
156 | return 0; | |
157 | ||
158 | return victor_unobfuscate(buf, rc, data); | |
159 | } | |
160 | ||
161 | /* Victor DMM cables are read-only. Just pretend successful transmission. */ | |
162 | static int victor_write_bytes(struct sr_serial_dev_inst *serial, | |
163 | const uint8_t *data, int size) | |
164 | { | |
165 | (void)serial; | |
166 | (void)data; | |
167 | ||
168 | return size; | |
169 | } | |
170 | ||
171 | static struct ser_hid_chip_functions chip_victor = { | |
172 | .chipname = "victor", | |
173 | .chipdesc = "Victor DMM scrambler", | |
174 | .vid_pid_items = vid_pid_items_victor, | |
175 | .max_bytes_per_request = VICTOR_DMM_PACKET_LENGTH, | |
c0aa074e UH |
176 | /* |
177 | * The USB HID connection has no concept of UART bitrate or | |
178 | * frame format. Silently ignore the parameters. | |
179 | */ | |
180 | .set_params = std_dummy_set_params, | |
0cdb72c8 GS |
181 | .read_bytes = victor_read_bytes, |
182 | .write_bytes = victor_write_bytes, | |
183 | }; | |
184 | SR_PRIV struct ser_hid_chip_functions *ser_hid_chip_funcs_victor = &chip_victor; | |
185 | ||
186 | #else | |
187 | ||
188 | SR_PRIV struct ser_hid_chip_functions *ser_hid_chip_funcs_victor = NULL; | |
189 | ||
190 | #endif | |
191 | #endif |