--- /dev/null
+/*
+ * This file is part of the libsigrok project.
+ *
+ * Copyright (C) 2019 Gerhard Sittig <gerhard.sittig@gmx.net>
+ *
+ * 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 <http://www.gnu.org/licenses/>.
+ */
+
+/*
+ * 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 <config.h>
+#include <glib.h>
+#include <libsigrok/libsigrok.h>
+#include "libsigrok-internal.h"
+#include "serial_hid.h"
+#include <string.h>
+
+/** @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
projects / libsigrok.git / commitdiff