serial-hid: add support for (scrambling) Victor DMM cables
Introduce a serial transport which undoes the Victor DMM cable's obfuscation to the DMM chip's original data packet. Which allows to re-use the existing FS9922 support code, obsoleting the victor-dmm device driver.
This commit is contained in:
Gerhard Sittig
parent
a89884c16c
commit
0cdb72c8f2
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@ -128,6 +128,7 @@ libsigrok_la_SOURCES += \
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src/serial_hid_bu86x.c \
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src/serial_hid_ch9325.c \
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src/serial_hid_cp2110.c \
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src/serial_hid_victor.c \
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src/serial_libsp.c \
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src/scpi/scpi_serial.c
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endif
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@ -758,6 +758,7 @@ struct sr_serial_dev_inst {
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SER_HID_CHIP_UNKNOWN, /**!< place holder */
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SER_HID_CHIP_BTC_BU86X, /**!< Brymen BU86x */
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SER_HID_CHIP_SIL_CP2110, /**!< SiLabs CP2110 */
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SER_HID_CHIP_VICTOR_DMM, /**!< Victor 70/86 DMM cable */
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SER_HID_CHIP_WCH_CH9325, /**!< WCH CH9325 */
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SER_HID_CHIP_LAST, /**!< sentinel */
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} hid_chip;
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@ -1251,6 +1252,7 @@ struct ser_hid_chip_functions {
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extern SR_PRIV struct ser_hid_chip_functions *ser_hid_chip_funcs_bu86x;
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extern SR_PRIV struct ser_hid_chip_functions *ser_hid_chip_funcs_ch9325;
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extern SR_PRIV struct ser_hid_chip_functions *ser_hid_chip_funcs_cp2110;
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extern SR_PRIV struct ser_hid_chip_functions *ser_hid_chip_funcs_victor;
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SR_PRIV const char *ser_hid_chip_find_name_vid_pid(uint16_t vid, uint16_t pid);
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#endif
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#endif
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@ -552,6 +552,7 @@ static struct ser_hid_chip_functions **chips[SER_HID_CHIP_LAST] = {
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[SER_HID_CHIP_UNKNOWN] = NULL,
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[SER_HID_CHIP_BTC_BU86X] = &ser_hid_chip_funcs_bu86x,
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[SER_HID_CHIP_SIL_CP2110] = &ser_hid_chip_funcs_cp2110,
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[SER_HID_CHIP_VICTOR_DMM] = &ser_hid_chip_funcs_victor,
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[SER_HID_CHIP_WCH_CH9325] = &ser_hid_chip_funcs_ch9325,
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};
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@ -0,0 +1,207 @@
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/*
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* This file is part of the libsigrok project.
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*
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* Copyright (C) 2019 Gerhard Sittig <gerhard.sittig@gmx.net>
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*
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* This program is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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/*
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* This implements serial transport primitives for Victor DMM cables,
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* which forward normal DMM chips' protocols, but scramble the data in
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* the process of forwarding. Just undoing the cable's scrambling at
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* the serial communication level allows full re-use of existing DMM
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* drivers, instead of creating Victor DMM specific support code.
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*
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* The cable's scrambling is somewhat complex:
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* - The order of bits within the bytes gets reversed.
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* - The order of bytes within the packet gets shuffled (randomly).
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* - The byte values randomly get mapped to other values by adding a
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* sequence of magic values to packet's byte values.
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* None of this adds any value to the DMM chip vendor's protocol. It's
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* mere obfuscation and extra complexity for the receiving application.
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*/
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#include <config.h>
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#include <glib.h>
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#include <libsigrok/libsigrok.h>
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#include "libsigrok-internal.h"
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#include "serial_hid.h"
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#include <string.h>
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/** @cond PRIVATE */
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#define LOG_PREFIX "serial-victor"
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/** @endcond */
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#ifdef HAVE_SERIAL_COMM
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#ifdef HAVE_LIBHIDAPI
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/**
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* @file
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*
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* Support serial-over-HID, specifically the Victor 70/86 DMM cables.
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*/
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#define VICTOR_DMM_PACKET_LENGTH 14
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static const struct vid_pid_item vid_pid_items_victor[] = {
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{ 0x1244, 0xd237, },
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VID_PID_TERM,
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};
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static int victor_set_params(struct sr_serial_dev_inst *serial,
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int baudrate, int bits, int parity, int stopbits,
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int flowcontrol, int rts, int dtr)
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{
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/*
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* The USB HID connection has no concept of UART bitrate or
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* frame format. Silently ignore the parameters.
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*/
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(void)serial;
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(void)baudrate;
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(void)bits;
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(void)parity;
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(void)stopbits;
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(void)flowcontrol;
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(void)rts;
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(void)dtr;
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return SR_OK;
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}
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/* Reverse bits within a byte. */
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static uint8_t bit_reverse(uint8_t b)
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{
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static const uint8_t rev_nibble[] = {
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0x00, 0x08, 0x04, 0x0c, 0x02, 0x0a, 0x06, 0x0e,
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0x01, 0x09, 0x05, 0x0d, 0x03, 0x0b, 0x07, 0x0f,
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};
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return (rev_nibble[(b >> 4) & 0xf]) |
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(rev_nibble[b & 0xf] << 4);
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}
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/*
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* The cable receives data by means of HID reports (simple data stream,
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* HID report encapsulation was already trimmed). Assume that received
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* data "is aligned", cope with zero or one 14-byte packets here, but
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* don't try to even bother with odd-length reception units. Also drop
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* the "all-zero" packets here which victor_dmm_receive_data() used to
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* eliminate at the device driver level in the past.
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*/
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static int victor_unobfuscate(uint8_t *rx_buf, size_t rx_len,
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uint8_t *ret_buf)
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{
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static const uint8_t obfuscation[VICTOR_DMM_PACKET_LENGTH] = {
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'j', 'o', 'd', 'e', 'n', 'x', 'u', 'n', 'i', 'c', 'k', 'x', 'i', 'a',
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};
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static const uint8_t shuffle[VICTOR_DMM_PACKET_LENGTH] = {
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6, 13, 5, 11, 2, 7, 9, 8, 3, 10, 12, 0, 4, 1
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};
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GString *txt;
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int is_zero;
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size_t idx, to_idx;
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if (sr_log_loglevel_get() >= SR_LOG_SPEW) {
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txt = sr_hexdump_new(rx_buf, rx_len);
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sr_spew("Received %zu bytes: %s.", rx_len, txt->str);
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sr_hexdump_free(txt);
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}
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/* Pass unexpected data in verbatim form. */
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if (rx_len != VICTOR_DMM_PACKET_LENGTH) {
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memcpy(ret_buf, rx_buf, rx_len);
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return rx_len;
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}
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/* Check for and discard all-zero packets. */
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is_zero = 1;
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for (idx = 0; is_zero && idx < VICTOR_DMM_PACKET_LENGTH; idx++) {
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if (rx_buf[idx])
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is_zero = 0;
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}
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if (is_zero) {
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sr_dbg("Received all zeroes packet, discarding.");
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return 0;
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}
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/*
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* Unobfuscate data bytes by subtracting a magic pattern, shuffle
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* the bits and bytes into the DMM chip's original order.
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*/
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for (idx = 0; idx < VICTOR_DMM_PACKET_LENGTH; idx++) {
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to_idx = VICTOR_DMM_PACKET_LENGTH - 1 - shuffle[idx];
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ret_buf[to_idx] = bit_reverse(rx_buf[idx] - obfuscation[idx]);
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}
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if (sr_log_loglevel_get() >= SR_LOG_SPEW) {
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txt = sr_hexdump_new(ret_buf, idx);
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sr_spew("Deobfuscated: %s.", txt->str);
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sr_hexdump_free(txt);
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}
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return rx_len;
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}
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/*
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* Read into a local buffer, and unobfuscate into the caller's buffer.
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* Always receive full DMM packets.
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*/
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static int victor_read_bytes(struct sr_serial_dev_inst *serial,
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uint8_t *data, int space, unsigned int timeout)
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{
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uint8_t buf[VICTOR_DMM_PACKET_LENGTH];
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int rc;
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if (space != sizeof(buf))
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space = sizeof(buf);
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rc = ser_hid_hidapi_get_data(serial, 0, buf, space, timeout);
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if (rc == SR_ERR_TIMEOUT)
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return 0;
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if (rc < 0)
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return rc;
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if (rc == 0)
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return 0;
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return victor_unobfuscate(buf, rc, data);
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}
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/* Victor DMM cables are read-only. Just pretend successful transmission. */
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static int victor_write_bytes(struct sr_serial_dev_inst *serial,
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const uint8_t *data, int size)
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{
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(void)serial;
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(void)data;
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return size;
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}
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static struct ser_hid_chip_functions chip_victor = {
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.chipname = "victor",
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.chipdesc = "Victor DMM scrambler",
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.vid_pid_items = vid_pid_items_victor,
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.max_bytes_per_request = VICTOR_DMM_PACKET_LENGTH,
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.set_params = victor_set_params,
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.read_bytes = victor_read_bytes,
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.write_bytes = victor_write_bytes,
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};
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SR_PRIV struct ser_hid_chip_functions *ser_hid_chip_funcs_victor = &chip_victor;
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#else
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SR_PRIV struct ser_hid_chip_functions *ser_hid_chip_funcs_victor = NULL;
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#endif
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#endif
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