From: Gerhard Sittig Date: Mon, 10 Jun 2019 18:15:24 +0000 (+0200) Subject: serial-hid: add support for (scrambling) Victor DMM cables X-Git-Url: https://sigrok.org/gitaction?a=commitdiff_plain;h=0cdb72c8f2e45fd6c744de426b2f00b207fba4f9;p=libsigrok.git 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. --- diff --git a/Makefile.am b/Makefile.am index 42759739..1a930e8c 100644 --- a/Makefile.am +++ b/Makefile.am @@ -128,6 +128,7 @@ libsigrok_la_SOURCES += \ src/serial_hid_bu86x.c \ src/serial_hid_ch9325.c \ src/serial_hid_cp2110.c \ + src/serial_hid_victor.c \ src/serial_libsp.c \ src/scpi/scpi_serial.c endif diff --git a/src/libsigrok-internal.h b/src/libsigrok-internal.h index ea444823..9df33ca3 100644 --- a/src/libsigrok-internal.h +++ b/src/libsigrok-internal.h @@ -758,6 +758,7 @@ struct sr_serial_dev_inst { SER_HID_CHIP_UNKNOWN, /**!< place holder */ SER_HID_CHIP_BTC_BU86X, /**!< Brymen BU86x */ SER_HID_CHIP_SIL_CP2110, /**!< SiLabs CP2110 */ + SER_HID_CHIP_VICTOR_DMM, /**!< Victor 70/86 DMM cable */ SER_HID_CHIP_WCH_CH9325, /**!< WCH CH9325 */ SER_HID_CHIP_LAST, /**!< sentinel */ } hid_chip; @@ -1251,6 +1252,7 @@ struct ser_hid_chip_functions { extern SR_PRIV struct ser_hid_chip_functions *ser_hid_chip_funcs_bu86x; extern SR_PRIV struct ser_hid_chip_functions *ser_hid_chip_funcs_ch9325; extern SR_PRIV struct ser_hid_chip_functions *ser_hid_chip_funcs_cp2110; +extern SR_PRIV struct ser_hid_chip_functions *ser_hid_chip_funcs_victor; SR_PRIV const char *ser_hid_chip_find_name_vid_pid(uint16_t vid, uint16_t pid); #endif #endif diff --git a/src/serial_hid.c b/src/serial_hid.c index 1aca73e6..d2776fc7 100644 --- a/src/serial_hid.c +++ b/src/serial_hid.c @@ -552,6 +552,7 @@ static struct ser_hid_chip_functions **chips[SER_HID_CHIP_LAST] = { [SER_HID_CHIP_UNKNOWN] = NULL, [SER_HID_CHIP_BTC_BU86X] = &ser_hid_chip_funcs_bu86x, [SER_HID_CHIP_SIL_CP2110] = &ser_hid_chip_funcs_cp2110, + [SER_HID_CHIP_VICTOR_DMM] = &ser_hid_chip_funcs_victor, [SER_HID_CHIP_WCH_CH9325] = &ser_hid_chip_funcs_ch9325, }; diff --git a/src/serial_hid_victor.c b/src/serial_hid_victor.c new file mode 100644 index 00000000..59f11c16 --- /dev/null +++ b/src/serial_hid_victor.c @@ -0,0 +1,207 @@ +/* + * This file is part of the libsigrok project. + * + * Copyright (C) 2019 Gerhard Sittig + * + * This program is free software: you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation, either version 3 of the License, or + * (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program. If not, see . + */ + +/* + * This implements serial transport primitives for Victor DMM cables, + * which forward normal DMM chips' protocols, but scramble the data in + * the process of forwarding. Just undoing the cable's scrambling at + * the serial communication level allows full re-use of existing DMM + * drivers, instead of creating Victor DMM specific support code. + * + * The cable's scrambling is somewhat complex: + * - The order of bits within the bytes gets reversed. + * - The order of bytes within the packet gets shuffled (randomly). + * - The byte values randomly get mapped to other values by adding a + * sequence of magic values to packet's byte values. + * None of this adds any value to the DMM chip vendor's protocol. It's + * mere obfuscation and extra complexity for the receiving application. + */ + +#include +#include +#include +#include "libsigrok-internal.h" +#include "serial_hid.h" +#include + +/** @cond PRIVATE */ +#define LOG_PREFIX "serial-victor" +/** @endcond */ + +#ifdef HAVE_SERIAL_COMM +#ifdef HAVE_LIBHIDAPI + +/** + * @file + * + * Support serial-over-HID, specifically the Victor 70/86 DMM cables. + */ + +#define VICTOR_DMM_PACKET_LENGTH 14 + +static const struct vid_pid_item vid_pid_items_victor[] = { + { 0x1244, 0xd237, }, + VID_PID_TERM, +}; + +static int victor_set_params(struct sr_serial_dev_inst *serial, + int baudrate, int bits, int parity, int stopbits, + int flowcontrol, int rts, int dtr) +{ + /* + * The USB HID connection has no concept of UART bitrate or + * frame format. Silently ignore the parameters. + */ + (void)serial; + (void)baudrate; + (void)bits; + (void)parity; + (void)stopbits; + (void)flowcontrol; + (void)rts; + (void)dtr; + + return SR_OK; +} + +/* Reverse bits within a byte. */ +static uint8_t bit_reverse(uint8_t b) +{ + static const uint8_t rev_nibble[] = { + 0x00, 0x08, 0x04, 0x0c, 0x02, 0x0a, 0x06, 0x0e, + 0x01, 0x09, 0x05, 0x0d, 0x03, 0x0b, 0x07, 0x0f, + }; + + return (rev_nibble[(b >> 4) & 0xf]) | + (rev_nibble[b & 0xf] << 4); +} + +/* + * The cable receives data by means of HID reports (simple data stream, + * HID report encapsulation was already trimmed). Assume that received + * data "is aligned", cope with zero or one 14-byte packets here, but + * don't try to even bother with odd-length reception units. Also drop + * the "all-zero" packets here which victor_dmm_receive_data() used to + * eliminate at the device driver level in the past. + */ +static int victor_unobfuscate(uint8_t *rx_buf, size_t rx_len, + uint8_t *ret_buf) +{ + static const uint8_t obfuscation[VICTOR_DMM_PACKET_LENGTH] = { + 'j', 'o', 'd', 'e', 'n', 'x', 'u', 'n', 'i', 'c', 'k', 'x', 'i', 'a', + }; + static const uint8_t shuffle[VICTOR_DMM_PACKET_LENGTH] = { + 6, 13, 5, 11, 2, 7, 9, 8, 3, 10, 12, 0, 4, 1 + }; + + GString *txt; + int is_zero; + size_t idx, to_idx; + + if (sr_log_loglevel_get() >= SR_LOG_SPEW) { + txt = sr_hexdump_new(rx_buf, rx_len); + sr_spew("Received %zu bytes: %s.", rx_len, txt->str); + sr_hexdump_free(txt); + } + + /* Pass unexpected data in verbatim form. */ + if (rx_len != VICTOR_DMM_PACKET_LENGTH) { + memcpy(ret_buf, rx_buf, rx_len); + return rx_len; + } + + /* Check for and discard all-zero packets. */ + is_zero = 1; + for (idx = 0; is_zero && idx < VICTOR_DMM_PACKET_LENGTH; idx++) { + if (rx_buf[idx]) + is_zero = 0; + } + if (is_zero) { + sr_dbg("Received all zeroes packet, discarding."); + return 0; + } + + /* + * Unobfuscate data bytes by subtracting a magic pattern, shuffle + * the bits and bytes into the DMM chip's original order. + */ + for (idx = 0; idx < VICTOR_DMM_PACKET_LENGTH; idx++) { + to_idx = VICTOR_DMM_PACKET_LENGTH - 1 - shuffle[idx]; + ret_buf[to_idx] = bit_reverse(rx_buf[idx] - obfuscation[idx]); + } + + if (sr_log_loglevel_get() >= SR_LOG_SPEW) { + txt = sr_hexdump_new(ret_buf, idx); + sr_spew("Deobfuscated: %s.", txt->str); + sr_hexdump_free(txt); + } + + return rx_len; +} + +/* + * Read into a local buffer, and unobfuscate into the caller's buffer. + * Always receive full DMM packets. + */ +static int victor_read_bytes(struct sr_serial_dev_inst *serial, + uint8_t *data, int space, unsigned int timeout) +{ + uint8_t buf[VICTOR_DMM_PACKET_LENGTH]; + int rc; + + if (space != sizeof(buf)) + space = sizeof(buf); + rc = ser_hid_hidapi_get_data(serial, 0, buf, space, timeout); + if (rc == SR_ERR_TIMEOUT) + return 0; + if (rc < 0) + return rc; + if (rc == 0) + return 0; + + return victor_unobfuscate(buf, rc, data); +} + +/* Victor DMM cables are read-only. Just pretend successful transmission. */ +static int victor_write_bytes(struct sr_serial_dev_inst *serial, + const uint8_t *data, int size) +{ + (void)serial; + (void)data; + + return size; +} + +static struct ser_hid_chip_functions chip_victor = { + .chipname = "victor", + .chipdesc = "Victor DMM scrambler", + .vid_pid_items = vid_pid_items_victor, + .max_bytes_per_request = VICTOR_DMM_PACKET_LENGTH, + .set_params = victor_set_params, + .read_bytes = victor_read_bytes, + .write_bytes = victor_write_bytes, +}; +SR_PRIV struct ser_hid_chip_functions *ser_hid_chip_funcs_victor = &chip_victor; + +#else + +SR_PRIV struct ser_hid_chip_functions *ser_hid_chip_funcs_victor = NULL; + +#endif +#endif