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0cdb72c8 GS |
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 | ||
0cdb72c8 | 43 | #define LOG_PREFIX "serial-victor" |
0cdb72c8 GS |
44 | |
45 | #ifdef HAVE_SERIAL_COMM | |
46 | #ifdef HAVE_LIBHIDAPI | |
47 | ||
48 | /** | |
49 | * @file | |
50 | * | |
51 | * Support serial-over-HID, specifically the Victor 70/86 DMM cables. | |
52 | */ | |
53 | ||
54 | #define VICTOR_DMM_PACKET_LENGTH 14 | |
55 | ||
56 | static const struct vid_pid_item vid_pid_items_victor[] = { | |
57 | { 0x1244, 0xd237, }, | |
9451e01e | 58 | ALL_ZERO |
0cdb72c8 GS |
59 | }; |
60 | ||
0cdb72c8 GS |
61 | /* Reverse bits within a byte. */ |
62 | static uint8_t bit_reverse(uint8_t b) | |
63 | { | |
64 | static const uint8_t rev_nibble[] = { | |
65 | 0x00, 0x08, 0x04, 0x0c, 0x02, 0x0a, 0x06, 0x0e, | |
66 | 0x01, 0x09, 0x05, 0x0d, 0x03, 0x0b, 0x07, 0x0f, | |
67 | }; | |
68 | ||
69 | return (rev_nibble[(b >> 4) & 0xf]) | | |
70 | (rev_nibble[b & 0xf] << 4); | |
71 | } | |
72 | ||
73 | /* | |
74 | * The cable receives data by means of HID reports (simple data stream, | |
75 | * HID report encapsulation was already trimmed). Assume that received | |
76 | * data "is aligned", cope with zero or one 14-byte packets here, but | |
77 | * don't try to even bother with odd-length reception units. Also drop | |
78 | * the "all-zero" packets here which victor_dmm_receive_data() used to | |
79 | * eliminate at the device driver level in the past. | |
80 | */ | |
81 | static int victor_unobfuscate(uint8_t *rx_buf, size_t rx_len, | |
82 | uint8_t *ret_buf) | |
83 | { | |
84 | static const uint8_t obfuscation[VICTOR_DMM_PACKET_LENGTH] = { | |
85 | 'j', 'o', 'd', 'e', 'n', 'x', 'u', 'n', 'i', 'c', 'k', 'x', 'i', 'a', | |
86 | }; | |
87 | static const uint8_t shuffle[VICTOR_DMM_PACKET_LENGTH] = { | |
88 | 6, 13, 5, 11, 2, 7, 9, 8, 3, 10, 12, 0, 4, 1 | |
89 | }; | |
90 | ||
91 | GString *txt; | |
92 | int is_zero; | |
93 | size_t idx, to_idx; | |
94 | ||
95 | if (sr_log_loglevel_get() >= SR_LOG_SPEW) { | |
96 | txt = sr_hexdump_new(rx_buf, rx_len); | |
97 | sr_spew("Received %zu bytes: %s.", rx_len, txt->str); | |
98 | sr_hexdump_free(txt); | |
99 | } | |
100 | ||
101 | /* Pass unexpected data in verbatim form. */ | |
102 | if (rx_len != VICTOR_DMM_PACKET_LENGTH) { | |
103 | memcpy(ret_buf, rx_buf, rx_len); | |
104 | return rx_len; | |
105 | } | |
106 | ||
107 | /* Check for and discard all-zero packets. */ | |
108 | is_zero = 1; | |
109 | for (idx = 0; is_zero && idx < VICTOR_DMM_PACKET_LENGTH; idx++) { | |
110 | if (rx_buf[idx]) | |
111 | is_zero = 0; | |
112 | } | |
113 | if (is_zero) { | |
114 | sr_dbg("Received all zeroes packet, discarding."); | |
115 | return 0; | |
116 | } | |
117 | ||
118 | /* | |
119 | * Unobfuscate data bytes by subtracting a magic pattern, shuffle | |
120 | * the bits and bytes into the DMM chip's original order. | |
121 | */ | |
122 | for (idx = 0; idx < VICTOR_DMM_PACKET_LENGTH; idx++) { | |
123 | to_idx = VICTOR_DMM_PACKET_LENGTH - 1 - shuffle[idx]; | |
124 | ret_buf[to_idx] = bit_reverse(rx_buf[idx] - obfuscation[idx]); | |
125 | } | |
126 | ||
127 | if (sr_log_loglevel_get() >= SR_LOG_SPEW) { | |
128 | txt = sr_hexdump_new(ret_buf, idx); | |
129 | sr_spew("Deobfuscated: %s.", txt->str); | |
130 | sr_hexdump_free(txt); | |
131 | } | |
132 | ||
133 | return rx_len; | |
134 | } | |
135 | ||
136 | /* | |
137 | * Read into a local buffer, and unobfuscate into the caller's buffer. | |
138 | * Always receive full DMM packets. | |
139 | */ | |
140 | static int victor_read_bytes(struct sr_serial_dev_inst *serial, | |
141 | uint8_t *data, int space, unsigned int timeout) | |
142 | { | |
143 | uint8_t buf[VICTOR_DMM_PACKET_LENGTH]; | |
144 | int rc; | |
145 | ||
146 | if (space != sizeof(buf)) | |
147 | space = sizeof(buf); | |
148 | rc = ser_hid_hidapi_get_data(serial, 0, buf, space, timeout); | |
149 | if (rc == SR_ERR_TIMEOUT) | |
150 | return 0; | |
151 | if (rc < 0) | |
152 | return rc; | |
153 | if (rc == 0) | |
154 | return 0; | |
155 | ||
156 | return victor_unobfuscate(buf, rc, data); | |
157 | } | |
158 | ||
159 | /* Victor DMM cables are read-only. Just pretend successful transmission. */ | |
160 | static int victor_write_bytes(struct sr_serial_dev_inst *serial, | |
161 | const uint8_t *data, int size) | |
162 | { | |
163 | (void)serial; | |
164 | (void)data; | |
165 | ||
166 | return size; | |
167 | } | |
168 | ||
169 | static struct ser_hid_chip_functions chip_victor = { | |
170 | .chipname = "victor", | |
171 | .chipdesc = "Victor DMM scrambler", | |
172 | .vid_pid_items = vid_pid_items_victor, | |
173 | .max_bytes_per_request = VICTOR_DMM_PACKET_LENGTH, | |
c0aa074e UH |
174 | /* |
175 | * The USB HID connection has no concept of UART bitrate or | |
176 | * frame format. Silently ignore the parameters. | |
177 | */ | |
178 | .set_params = std_dummy_set_params, | |
0cdb72c8 GS |
179 | .read_bytes = victor_read_bytes, |
180 | .write_bytes = victor_write_bytes, | |
181 | }; | |
182 | SR_PRIV struct ser_hid_chip_functions *ser_hid_chip_funcs_victor = &chip_victor; | |
183 | ||
184 | #else | |
185 | ||
186 | SR_PRIV struct ser_hid_chip_functions *ser_hid_chip_funcs_victor = NULL; | |
187 | ||
188 | #endif | |
189 | #endif |