libsigrok/hardware/brymen-dmm/parser.c

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/*
* This file is part of the libsigrok project.
*
* Copyright (C) 2012 Alexandru Gagniuc <mr.nuke.me@gmail.com>
*
* 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/>.
*/
#include "protocol.h"
#define MAX_PACKET_LEN 22
/* Flags passed from the DMM. */
struct brymen_flags {
gboolean is_low_batt, is_decibel, is_duty_cycle, is_hertz, is_amp;
gboolean is_beep, is_ohm, is_fahrenheit, is_celsius, is_capacitance;
gboolean is_diode, is_volt, is_dc, is_ac;
};
struct bm850_command {
uint8_t dle;
uint8_t stx;
uint8_t cmd;
uint8_t arg[2];
uint8_t checksum;
uint8_t dle2;
uint8_t etx;
};
struct brymen_header {
uint8_t dle;
uint8_t stx;
uint8_t cmd;
uint8_t len;
};
struct brymen_tail {
uint8_t checksum;
uint8_t dle;
uint8_t etx;
};
/*
* We only have one command because we only support the BM-857. However, the
* driver is easily extensible to support more models, as the protocols are
* very similar.
*/
enum {
BM_CMD_REQUEST_READING = 0x00,
};
static int bm_send_command(uint8_t command, uint8_t arg1, uint8_t arg2,
struct sr_serial_dev_inst *serial)
{
struct bm850_command cmdout;
int written;
cmdout.dle = 0x10;
cmdout.stx = 0x02;
cmdout.cmd = command;
cmdout.arg[0] = arg1;
cmdout.arg[1] = arg2;
cmdout.checksum = arg1 ^ arg2;
cmdout.dle2 = 0x10;
cmdout.etx = 0x03;
/* TODO: How to compute the checksum? Hardware seems to ignore it. */
/* Request reading. */
written = serial_write(serial, &cmdout, sizeof(cmdout));
if (written != sizeof(cmdout))
return SR_ERR;
return SR_OK;
}
SR_PRIV int brymen_packet_request(struct sr_serial_dev_inst *serial)
{
return bm_send_command(BM_CMD_REQUEST_READING, 0, 0, serial);
}
SR_PRIV int brymen_packet_length(const uint8_t *buf, int *len)
{
struct brymen_header *hdr;
int packet_len;
size_t buflen;
buflen = *len;
hdr = (void *)buf;
/* Did we receive a complete header yet? */
if (buflen < sizeof(*hdr))
return PACKET_NEED_MORE_DATA;
if (hdr->dle != 0x10 || hdr->stx != 0x02)
return PACKET_INVALID_HEADER;
/* Our packet includes the header, the payload, and the tail. */
packet_len = sizeof(*hdr) + hdr->len + sizeof(struct brymen_tail);
/* In case we pick up an invalid header, limit our search. */
if (packet_len > MAX_PACKET_LEN) {
sr_spew("Header specifies an invalid payload length: %i.",
hdr->len);
return PACKET_INVALID_HEADER;
}
*len = packet_len;
sr_spew("Expecting a %d-byte packet.", *len);
return PACKET_HEADER_OK;
}
SR_PRIV gboolean brymen_packet_is_valid(const uint8_t *buf)
{
struct brymen_header *hdr;
struct brymen_tail *tail;
int i;
uint8_t chksum = 0;
uint8_t *payload;
payload = (uint8_t *)(buf + sizeof(struct brymen_header));
hdr = (void *)buf;
tail = (void *)(payload + hdr->len);
for (i = 0; i< hdr->len; i++)
chksum ^= payload[i];
if (tail->checksum != chksum) {
sr_dbg("Packet has invalid checksum 0x%.2x. Expected 0x%.2x.",
chksum, tail->checksum);
return FALSE;
}
return TRUE;
}
static int parse_value(const char *strbuf, int len, float *floatval)
{
int s, d;
char str[32];
if (strstr(strbuf, "OL")) {
sr_dbg("Overlimit.");
*floatval = INFINITY;
return SR_OK;
}
memset(str, 0, sizeof(str));
/* Spaces may interfere with strtod parsing the exponent. Strip them. */
for (s = 0, d = 0; s < len; s++)
if (strbuf[s] != ' ')
str[d++] = strbuf[s];
/* Yes, it's that simple! */
*floatval = strtod(str, NULL);
return SR_OK;
}
static void parse_flags(const uint8_t *buf, struct brymen_flags *info)
{
info->is_low_batt = (buf[4 + 3] & (1 << 7)) != 0;
info->is_decibel = (buf[4 + 1] & (1 << 5)) != 0;
info->is_duty_cycle = (buf[4 + 1] & (1 << 3)) != 0;
info->is_hertz = (buf[4 + 1] & (1 << 2)) != 0;
info->is_amp = (buf[4 + 1] & (1 << 1)) != 0;
info->is_beep = (buf[4 + 1] & (1 << 0)) != 0;
info->is_ohm = (buf[4 + 0] & (1 << 7)) != 0;
info->is_fahrenheit = (buf[4 + 0] & (1 << 6)) != 0;
info->is_celsius = (buf[4 + 0] & (1 << 5)) != 0;
info->is_diode = (buf[4 + 0] & (1 << 4)) != 0;
info->is_capacitance = (buf[4 + 0] & (1 << 3)) != 0;
info->is_volt = (buf[4 + 0] & (1 << 2)) != 0;
info->is_dc = (buf[4 + 0] & (1 << 1)) != 0;
info->is_ac = (buf[4 + 0] & (1 << 0)) != 0;
}
SR_PRIV int sr_brymen_parse(const uint8_t *buf, float *floatval,
struct sr_datafeed_analog *analog, void *info)
{
struct brymen_flags flags;
struct brymen_header *hdr;
uint8_t *bfunc;
int asciilen;
(void)info;
hdr = (void *)buf;
bfunc = (uint8_t *)(buf + sizeof(struct brymen_header));
analog->mqflags = 0;
/* Give some debug info about the package. */
asciilen = hdr->len - 4;
sr_dbg("DMM flags: %.2x %.2x %.2x %.2x",
bfunc[3], bfunc[2], bfunc[1], bfunc[0]);
/* Value is an ASCII string. */
sr_dbg("DMM packet: \"%.*s\"", asciilen, bfunc + 4);
parse_flags(buf, &flags);
parse_value((const char *)(bfunc + 4), asciilen, floatval);
if (flags.is_volt) {
analog->mq = SR_MQ_VOLTAGE;
analog->unit = SR_UNIT_VOLT;
}
if (flags.is_amp) {
analog->mq = SR_MQ_CURRENT;
analog->unit = SR_UNIT_AMPERE;
}
if (flags.is_ohm) {
if (flags.is_beep)
analog->mq = SR_MQ_CONTINUITY;
else
analog->mq = SR_MQ_RESISTANCE;
analog->unit = SR_UNIT_OHM;
}
if (flags.is_hertz) {
analog->mq = SR_MQ_FREQUENCY;
analog->unit = SR_UNIT_HERTZ;
}
if (flags.is_duty_cycle) {
analog->mq = SR_MQ_DUTY_CYCLE;
analog->unit = SR_UNIT_PERCENTAGE;
}
if (flags.is_capacitance) {
analog->mq = SR_MQ_CAPACITANCE;
analog->unit = SR_UNIT_FARAD;
}
if (flags.is_fahrenheit) {
analog->mq = SR_MQ_TEMPERATURE;
analog->unit = SR_UNIT_FAHRENHEIT;
}
if (flags.is_celsius) {
analog->mq = SR_MQ_TEMPERATURE;
analog->unit = SR_UNIT_CELSIUS;
}
if (flags.is_capacitance) {
analog->mq = SR_MQ_CAPACITANCE;
analog->unit = SR_UNIT_FARAD;
}
/*
* The high-end Brymen models have a configurable reference impedance.
* When the reference impedance is changed, the DMM sends one packet
* with the value of the new reference impedance. Both decibel and ohm
* flags are set in this case, so we must be careful to correctly
* identify the value as ohm, not dBmW.
*/
if (flags.is_decibel && !flags.is_ohm) {
analog->mq = SR_MQ_POWER;
analog->unit = SR_UNIT_DECIBEL_MW;
/*
* For some reason, dBm measurements are sent by the multimeter
* with a value three orders of magnitude smaller than the
* displayed value.
*/
*floatval *= 1000;
}
if (flags.is_diode)
analog->mqflags |= SR_MQFLAG_DIODE;
/* We can have both AC+DC in a single measurement. */
if (flags.is_ac)
analog->mqflags |= SR_MQFLAG_AC;
if (flags.is_dc)
analog->mqflags |= SR_MQFLAG_DC;
if (flags.is_low_batt)
sr_info("Low battery!");
return SR_OK;
}