[libsigrok.git] / src / hardware / rdtech-tc / protocol.c

/*
 * This file is part of the libsigrok project.
 *
 * Copyright (C) 2020 Andreas Sandberg <andreas@sandberg.pp.se>
 *
 * 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 <config.h>

#include <glib.h>
#include <libsigrok/libsigrok.h>
#include <math.h>
#include <nettle/aes.h>
#include <stdlib.h>
#include <string.h>

#include "libsigrok-internal.h"
#include "protocol.h"

#define PROBE_TO_MS	1000
#define WRITE_TO_MS	1
#define POLL_PERIOD_MS	100

/*
 * Response data (raw sample data) consists of three adjacent chunks
 * of 64 bytes each. These chunks start with their magic string, and
 * end in a 32bit checksum field. Measurement values are scattered
 * across these 192 bytes total size. All multi-byte integer values
 * are represented in little endian format. Typical size is 32 bits.
 */

#define MAGIC_PAC1	0x70616331	/* 'pac1' */
#define MAGIC_PAC2	0x70616332	/* 'pac2' */
#define MAGIC_PAC3	0x70616333	/* 'pac3' */

#define PAC_LEN 64
#define PAC_CRC_POS (PAC_LEN - sizeof(uint32_t))

/* Offset to PAC block from start of poll data */
#define OFF_PAC1 (0 * PAC_LEN)
#define OFF_PAC2 (1 * PAC_LEN)
#define OFF_PAC3 (2 * PAC_LEN)
#define TC_POLL_LEN (3 * PAC_LEN)
#if TC_POLL_LEN > RDTECH_TC_RSPBUFSIZE
#  error "response length exceeds receive buffer space"
#endif

#define OFF_MODEL 4
#define LEN_MODEL 4

#define OFF_FW_VER 8
#define LEN_FW_VER 4

#define OFF_SERIAL 12

static const uint8_t aes_key[] = {
	0x58, 0x21, 0xfa, 0x56, 0x01, 0xb2, 0xf0, 0x26,
	0x87, 0xff, 0x12, 0x04, 0x62, 0x2a, 0x4f, 0xb0,
	0x86, 0xf4, 0x02, 0x60, 0x81, 0x6f, 0x9a, 0x0b,
	0xa7, 0xf1, 0x06, 0x61, 0x9a, 0xb8, 0x72, 0x88,
};

static const struct rdtech_tc_channel_desc rdtech_tc_channels[] = {
	{ "V",  {   0 + 48, BVT_LE_UINT32, }, { 100, 1e6, }, 4, SR_MQ_VOLTAGE, SR_UNIT_VOLT },
	{ "I",  {   0 + 52, BVT_LE_UINT32, }, {  10, 1e6, }, 5, SR_MQ_CURRENT, SR_UNIT_AMPERE },
	{ "D+", {  64 + 32, BVT_LE_UINT32, }, {  10, 1e3, }, 2, SR_MQ_VOLTAGE, SR_UNIT_VOLT },
	{ "D-", {  64 + 36, BVT_LE_UINT32, }, {  10, 1e3, }, 2, SR_MQ_VOLTAGE, SR_UNIT_VOLT },
	{ "E0", {  64 + 12, BVT_LE_UINT32, }, {   1, 1e3, }, 3, SR_MQ_ENERGY, SR_UNIT_WATT_HOUR },
	{ "E1", {  64 + 20, BVT_LE_UINT32, }, {   1, 1e3, }, 3, SR_MQ_ENERGY, SR_UNIT_WATT_HOUR },
};

static gboolean check_pac_crc(uint8_t *data)
{
	uint16_t crc_calc;
	uint32_t crc_recv;

	crc_calc = sr_crc16(SR_CRC16_DEFAULT_INIT, data, PAC_CRC_POS);
	crc_recv = read_u32le(&data[PAC_CRC_POS]);
	if (crc_calc != crc_recv) {
		sr_spew("CRC error. Calculated: %0x" PRIx16 ", expected: %0x" PRIx32,
			crc_calc, crc_recv);
		return FALSE;
	}

	return TRUE;
}

static int process_poll_pkt(struct dev_context *devc, uint8_t *dst)
{
	struct aes256_ctx ctx;
	gboolean ok;

	aes256_set_decrypt_key(&ctx, aes_key);
	aes256_decrypt(&ctx, TC_POLL_LEN, dst, devc->buf);

	ok = TRUE;
	ok &= read_u32be(&dst[OFF_PAC1]) == MAGIC_PAC1;
	ok &= read_u32be(&dst[OFF_PAC2]) == MAGIC_PAC2;
	ok &= read_u32be(&dst[OFF_PAC3]) == MAGIC_PAC3;
	if (!ok) {
		sr_err("Invalid poll response packet (magic values).");
		return SR_ERR_DATA;
	}

	ok &= check_pac_crc(&dst[OFF_PAC1]);
	ok &= check_pac_crc(&dst[OFF_PAC2]);
	ok &= check_pac_crc(&dst[OFF_PAC3]);
	if (!ok) {
		sr_err("Invalid poll response packet (checksum).");
		return SR_ERR_DATA;
	}

	if (sr_log_loglevel_get() >= SR_LOG_SPEW) {
		static const size_t chunk_max = 32;

		const uint8_t *rdptr;
		size_t rdlen, chunk_addr, chunk_len;
		GString *txt;

		sr_spew("check passed on decrypted receive data");
		rdptr = dst;
		rdlen = TC_POLL_LEN;
		chunk_addr = 0;
		while (rdlen) {
			chunk_len = rdlen;
			if (chunk_len > chunk_max)
				chunk_len = chunk_max;
			txt = sr_hexdump_new(rdptr, chunk_len);
			sr_spew("%04zx  %s", chunk_addr, txt->str);
			sr_hexdump_free(txt);
			chunk_addr += chunk_len;
			rdptr += chunk_len;
			rdlen -= chunk_len;
		}
	}

	return SR_OK;
}

SR_PRIV int rdtech_tc_probe(struct sr_serial_dev_inst *serial, struct dev_context *devc)
{
	static const char *poll_cmd_cdc = "getva";
	static const char *poll_cmd_ble = "bgetva\r\n";

	int len;
	uint8_t poll_pkt[TC_POLL_LEN];

	/* Construct the request text. Which differs across transports. */
	devc->is_bluetooth = ser_name_is_bt(serial);
	snprintf(devc->req_text, sizeof(devc->req_text), "%s",
		devc->is_bluetooth ? poll_cmd_ble : poll_cmd_cdc);
	sr_dbg("is bluetooth %d -> poll request '%s'.",
		devc->is_bluetooth, devc->req_text);

	/* Transmit the request. */
	len = serial_write_blocking(serial,
		devc->req_text, strlen(devc->req_text), WRITE_TO_MS);
	if (len < 0) {
		sr_err("Failed to send probe request.");
		return SR_ERR;
	}

	/* Receive a response. */
	len = serial_read_blocking(serial, devc->buf, TC_POLL_LEN, PROBE_TO_MS);
	if (len != TC_POLL_LEN) {
		sr_err("Failed to read probe response.");
		return SR_ERR;
	}

	if (process_poll_pkt(devc, poll_pkt) != SR_OK) {
		sr_err("Unrecognized TC device!");
		return SR_ERR;
	}

	devc->channels = rdtech_tc_channels;
	devc->channel_count = ARRAY_SIZE(rdtech_tc_channels);
	devc->dev_info.model_name = g_strndup((const char *)&poll_pkt[OFF_MODEL], LEN_MODEL);
	devc->dev_info.fw_ver = g_strndup((const char *)&poll_pkt[OFF_FW_VER], LEN_FW_VER);
	devc->dev_info.serial_num = read_u32le(&poll_pkt[OFF_SERIAL]);

	return SR_OK;
}

SR_PRIV int rdtech_tc_poll(const struct sr_dev_inst *sdi, gboolean force)
{
	struct dev_context *devc;
	int64_t now, elapsed;
	struct sr_serial_dev_inst *serial;
	int len;

	/*
	 * Don't send the request while receive data is being accumulated.
	 * Defer request transmission when a previous request has not yet
	 * seen any response data at all (more probable to happen shortly
	 * after connecting to the peripheral).
	 */
	devc = sdi->priv;
	if (!force) {
		if (devc->rdlen)
			return SR_OK;
		if (!devc->rx_after_tx)
			return SR_OK;
	}

	/*
	 * Send the request when the transmit interval was reached. Or
	 * when the caller forced the transmission.
	 */
	now = g_get_monotonic_time() / 1000;
	elapsed = now - devc->cmd_sent_at;
	if (!force && elapsed < POLL_PERIOD_MS)
		return SR_OK;

	/*
	 * Transmit another measurement request. Only advance the
	 * interval after successful transmission.
	 */
	serial = sdi->conn;
	len = serial_write_blocking(serial,
		devc->req_text, strlen(devc->req_text), WRITE_TO_MS);
	if (len < 0) {
		sr_err("Unable to send poll request.");
		return SR_ERR;
	}
	devc->cmd_sent_at = now;
	devc->rx_after_tx = 0;

	return SR_OK;
}

static int handle_poll_data(struct sr_dev_inst *sdi)
{
	struct dev_context *devc;
	uint8_t poll_pkt[TC_POLL_LEN];
	size_t ch_idx;
	const struct rdtech_tc_channel_desc *pch;
	int ret;
	float v;

	devc = sdi->priv;
	sr_spew("Received poll packet (len: %zu).", devc->rdlen);
	if (devc->rdlen < TC_POLL_LEN) {
		sr_err("Insufficient poll packet length: %zu", devc->rdlen);
		return SR_ERR_DATA;
	}

	if (process_poll_pkt(devc, poll_pkt) != SR_OK) {
		sr_err("Failed to process poll packet.");
		return SR_ERR_DATA;
	}

	ret = SR_OK;
	std_session_send_df_frame_begin(sdi);
	for (ch_idx = 0; ch_idx < devc->channel_count; ch_idx++) {
		pch = &devc->channels[ch_idx];
		ret = bv_get_value_len(&v, &pch->spec, poll_pkt, TC_POLL_LEN);
		if (ret != SR_OK)
			break;
		ret = feed_queue_analog_submit_one(devc->feeds[ch_idx], v, 1);
		if (ret != SR_OK)
			break;
	}
	std_session_send_df_frame_end(sdi);

	sr_sw_limits_update_frames_read(&devc->limits, 1);
	if (sr_sw_limits_check(&devc->limits))
		sr_dev_acquisition_stop(sdi);

	return ret;
}

static int recv_poll_data(struct sr_dev_inst *sdi, struct sr_serial_dev_inst *serial)
{
	struct dev_context *devc;
	size_t space;
	int len;
	int ret;

	/* Receive data became available. Drain the transport layer. */
	devc = sdi->priv;
	while (devc->rdlen < TC_POLL_LEN) {
		space = sizeof(devc->buf) - devc->rdlen;
		len = serial_read_nonblocking(serial,
			&devc->buf[devc->rdlen], space);
		if (len < 0)
			return SR_ERR_IO;
		if (len == 0)
			return SR_OK;
		devc->rdlen += len;
		devc->rx_after_tx += len;
	}

	/*
	 * TODO Want to (re-)synchronize to the packet stream? The
	 * 'pac1' string literal would be a perfect match for that.
	 */

	/* Process packets when their reception has completed. */
	while (devc->rdlen >= TC_POLL_LEN) {
		ret = handle_poll_data(sdi);
		if (ret != SR_OK)
			return ret;
		devc->rdlen -= TC_POLL_LEN;
		if (devc->rdlen)
			memmove(devc->buf, &devc->buf[TC_POLL_LEN], devc->rdlen);
	}

	return SR_OK;
}

SR_PRIV int rdtech_tc_receive_data(int fd, int revents, void *cb_data)
{
	struct sr_dev_inst *sdi;
	struct dev_context *devc;
	struct sr_serial_dev_inst *serial;
	int ret;

	(void)fd;

	if (!(sdi = cb_data))
		return TRUE;
	if (!(devc = sdi->priv))
		return TRUE;

	/* Handle availability of receive data. */
	serial = sdi->conn;
	if (revents == G_IO_IN) {
		ret = recv_poll_data(sdi, serial);
		if (ret != SR_OK)
			sr_dev_acquisition_stop(sdi);
	}

	/* Check configured acquisition limits. */
	if (sr_sw_limits_check(&devc->limits)) {
		sr_dev_acquisition_stop(sdi);
		return TRUE;
	}

	/* Periodically retransmit measurement requests. */
	(void)rdtech_tc_poll(sdi, FALSE);

	return TRUE;
}
Commit	Line	Data
	1	/*
	2	* This file is part of the libsigrok project.
	3	*
	4	* Copyright (C) 2020 Andreas Sandberg <andreas@sandberg.pp.se>
	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	#include <config.h>
	21
	22	#include <glib.h>
	23	#include <libsigrok/libsigrok.h>
	24	#include <math.h>
	25	#include <nettle/aes.h>
	26	#include <stdlib.h>
	27	#include <string.h>
	28
	29	#include "libsigrok-internal.h"
	30	#include "protocol.h"
	31
	32	#define PROBE_TO_MS 1000
	33	#define WRITE_TO_MS 1
	34	#define POLL_PERIOD_MS 100
	35
	36	/*
	37	* Response data (raw sample data) consists of three adjacent chunks
	38	* of 64 bytes each. These chunks start with their magic string, and
	39	* end in a 32bit checksum field. Measurement values are scattered
	40	* across these 192 bytes total size. All multi-byte integer values
	41	* are represented in little endian format. Typical size is 32 bits.
	42	*/
	43
	44	#define MAGIC_PAC1 0x70616331 /* 'pac1' */
	45	#define MAGIC_PAC2 0x70616332 /* 'pac2' */
	46	#define MAGIC_PAC3 0x70616333 /* 'pac3' */
	47
	48	#define PAC_LEN 64
	49	#define PAC_CRC_POS (PAC_LEN - sizeof(uint32_t))
	50
	51	/* Offset to PAC block from start of poll data */
	52	#define OFF_PAC1 (0 * PAC_LEN)
	53	#define OFF_PAC2 (1 * PAC_LEN)
	54	#define OFF_PAC3 (2 * PAC_LEN)
	55	#define TC_POLL_LEN (3 * PAC_LEN)
	56	#if TC_POLL_LEN > RDTECH_TC_RSPBUFSIZE
	57	# error "response length exceeds receive buffer space"
	58	#endif
	59
	60	#define OFF_MODEL 4
	61	#define LEN_MODEL 4
	62
	63	#define OFF_FW_VER 8
	64	#define LEN_FW_VER 4
	65
	66	#define OFF_SERIAL 12
	67
	68	static const uint8_t aes_key[] = {
	69	0x58, 0x21, 0xfa, 0x56, 0x01, 0xb2, 0xf0, 0x26,
	70	0x87, 0xff, 0x12, 0x04, 0x62, 0x2a, 0x4f, 0xb0,
	71	0x86, 0xf4, 0x02, 0x60, 0x81, 0x6f, 0x9a, 0x0b,
	72	0xa7, 0xf1, 0x06, 0x61, 0x9a, 0xb8, 0x72, 0x88,
	73	};
	74
	75	static const struct rdtech_tc_channel_desc rdtech_tc_channels[] = {
	76	{ "V", { 0 + 48, BVT_LE_UINT32, }, { 100, 1e6, }, 4, SR_MQ_VOLTAGE, SR_UNIT_VOLT },
	77	{ "I", { 0 + 52, BVT_LE_UINT32, }, { 10, 1e6, }, 5, SR_MQ_CURRENT, SR_UNIT_AMPERE },
	78	{ "D+", { 64 + 32, BVT_LE_UINT32, }, { 10, 1e3, }, 2, SR_MQ_VOLTAGE, SR_UNIT_VOLT },
	79	{ "D-", { 64 + 36, BVT_LE_UINT32, }, { 10, 1e3, }, 2, SR_MQ_VOLTAGE, SR_UNIT_VOLT },
	80	{ "E0", { 64 + 12, BVT_LE_UINT32, }, { 1, 1e3, }, 3, SR_MQ_ENERGY, SR_UNIT_WATT_HOUR },
	81	{ "E1", { 64 + 20, BVT_LE_UINT32, }, { 1, 1e3, }, 3, SR_MQ_ENERGY, SR_UNIT_WATT_HOUR },
	82	};
	83
	84	static gboolean check_pac_crc(uint8_t *data)
	85	{
	86	uint16_t crc_calc;
	87	uint32_t crc_recv;
	88
	89	crc_calc = sr_crc16(SR_CRC16_DEFAULT_INIT, data, PAC_CRC_POS);
	90	crc_recv = read_u32le(&data[PAC_CRC_POS]);
	91	if (crc_calc != crc_recv) {
	92	sr_spew("CRC error. Calculated: %0x" PRIx16 ", expected: %0x" PRIx32,
	93	crc_calc, crc_recv);
	94	return FALSE;
	95	}
	96
	97	return TRUE;
	98	}
	99
	100	static int process_poll_pkt(struct dev_context devc, uint8_t dst)
	101	{
	102	struct aes256_ctx ctx;
	103	gboolean ok;
	104
	105	aes256_set_decrypt_key(&ctx, aes_key);
	106	aes256_decrypt(&ctx, TC_POLL_LEN, dst, devc->buf);
	107
	108	ok = TRUE;
	109	ok &= read_u32be(&dst[OFF_PAC1]) == MAGIC_PAC1;
	110	ok &= read_u32be(&dst[OFF_PAC2]) == MAGIC_PAC2;
	111	ok &= read_u32be(&dst[OFF_PAC3]) == MAGIC_PAC3;
	112	if (!ok) {
	113	sr_err("Invalid poll response packet (magic values).");
	114	return SR_ERR_DATA;
	115	}
	116
	117	ok &= check_pac_crc(&dst[OFF_PAC1]);
	118	ok &= check_pac_crc(&dst[OFF_PAC2]);
	119	ok &= check_pac_crc(&dst[OFF_PAC3]);
	120	if (!ok) {
	121	sr_err("Invalid poll response packet (checksum).");
	122	return SR_ERR_DATA;
	123	}
	124
	125	if (sr_log_loglevel_get() >= SR_LOG_SPEW) {
	126	static const size_t chunk_max = 32;
	127
	128	const uint8_t *rdptr;
	129	size_t rdlen, chunk_addr, chunk_len;
	130	GString *txt;
	131
	132	sr_spew("check passed on decrypted receive data");
	133	rdptr = dst;
	134	rdlen = TC_POLL_LEN;
	135	chunk_addr = 0;
	136	while (rdlen) {
	137	chunk_len = rdlen;
	138	if (chunk_len > chunk_max)
	139	chunk_len = chunk_max;
	140	txt = sr_hexdump_new(rdptr, chunk_len);
	141	sr_spew("%04zx %s", chunk_addr, txt->str);
	142	sr_hexdump_free(txt);
	143	chunk_addr += chunk_len;
	144	rdptr += chunk_len;
	145	rdlen -= chunk_len;
	146	}
	147	}
	148
	149	return SR_OK;
	150	}
	151
	152	SR_PRIV int rdtech_tc_probe(struct sr_serial_dev_inst serial, struct dev_context devc)
	153	{
	154	static const char *poll_cmd_cdc = "getva";
	155	static const char *poll_cmd_ble = "bgetva\r\n";
	156
	157	int len;
	158	uint8_t poll_pkt[TC_POLL_LEN];
	159
	160	/* Construct the request text. Which differs across transports. */
	161	devc->is_bluetooth = ser_name_is_bt(serial);
	162	snprintf(devc->req_text, sizeof(devc->req_text), "%s",
	163	devc->is_bluetooth ? poll_cmd_ble : poll_cmd_cdc);
	164	sr_dbg("is bluetooth %d -> poll request '%s'.",
	165	devc->is_bluetooth, devc->req_text);
	166
	167	/* Transmit the request. */
	168	len = serial_write_blocking(serial,
	169	devc->req_text, strlen(devc->req_text), WRITE_TO_MS);
	170	if (len < 0) {
	171	sr_err("Failed to send probe request.");
	172	return SR_ERR;
	173	}
	174
	175	/* Receive a response. */
	176	len = serial_read_blocking(serial, devc->buf, TC_POLL_LEN, PROBE_TO_MS);
	177	if (len != TC_POLL_LEN) {
	178	sr_err("Failed to read probe response.");
	179	return SR_ERR;
	180	}
	181
	182	if (process_poll_pkt(devc, poll_pkt) != SR_OK) {
	183	sr_err("Unrecognized TC device!");
	184	return SR_ERR;
	185	}
	186
	187	devc->channels = rdtech_tc_channels;
	188	devc->channel_count = ARRAY_SIZE(rdtech_tc_channels);
	189	devc->dev_info.model_name = g_strndup((const char *)&poll_pkt[OFF_MODEL], LEN_MODEL);
	190	devc->dev_info.fw_ver = g_strndup((const char *)&poll_pkt[OFF_FW_VER], LEN_FW_VER);
	191	devc->dev_info.serial_num = read_u32le(&poll_pkt[OFF_SERIAL]);
	192
	193	return SR_OK;
	194	}
	195
	196	SR_PRIV int rdtech_tc_poll(const struct sr_dev_inst *sdi, gboolean force)
	197	{
	198	struct dev_context *devc;
	199	int64_t now, elapsed;
	200	struct sr_serial_dev_inst *serial;
	201	int len;
	202
	203	/*
	204	* Don't send the request while receive data is being accumulated.
	205	* Defer request transmission when a previous request has not yet
	206	* seen any response data at all (more probable to happen shortly
	207	* after connecting to the peripheral).
	208	*/
	209	devc = sdi->priv;
	210	if (!force) {
	211	if (devc->rdlen)
	212	return SR_OK;
	213	if (!devc->rx_after_tx)
	214	return SR_OK;
	215	}
	216
	217	/*
	218	* Send the request when the transmit interval was reached. Or
	219	* when the caller forced the transmission.
	220	*/
	221	now = g_get_monotonic_time() / 1000;
	222	elapsed = now - devc->cmd_sent_at;
	223	if (!force && elapsed < POLL_PERIOD_MS)
	224	return SR_OK;
	225
	226	/*
	227	* Transmit another measurement request. Only advance the
	228	* interval after successful transmission.
	229	*/
	230	serial = sdi->conn;
	231	len = serial_write_blocking(serial,
	232	devc->req_text, strlen(devc->req_text), WRITE_TO_MS);
	233	if (len < 0) {
	234	sr_err("Unable to send poll request.");
	235	return SR_ERR;
	236	}
	237	devc->cmd_sent_at = now;
	238	devc->rx_after_tx = 0;
	239
	240	return SR_OK;
	241	}
	242
	243	static int handle_poll_data(struct sr_dev_inst *sdi)
	244	{
	245	struct dev_context *devc;
	246	uint8_t poll_pkt[TC_POLL_LEN];
	247	size_t ch_idx;
	248	const struct rdtech_tc_channel_desc *pch;
	249	int ret;
	250	float v;
	251
	252	devc = sdi->priv;
	253	sr_spew("Received poll packet (len: %zu).", devc->rdlen);
	254	if (devc->rdlen < TC_POLL_LEN) {
	255	sr_err("Insufficient poll packet length: %zu", devc->rdlen);
	256	return SR_ERR_DATA;
	257	}
	258
	259	if (process_poll_pkt(devc, poll_pkt) != SR_OK) {
	260	sr_err("Failed to process poll packet.");
	261	return SR_ERR_DATA;
	262	}
	263
	264	ret = SR_OK;
	265	std_session_send_df_frame_begin(sdi);
	266	for (ch_idx = 0; ch_idx < devc->channel_count; ch_idx++) {
	267	pch = &devc->channels[ch_idx];
	268	ret = bv_get_value_len(&v, &pch->spec, poll_pkt, TC_POLL_LEN);
	269	if (ret != SR_OK)
	270	break;
	271	ret = feed_queue_analog_submit_one(devc->feeds[ch_idx], v, 1);
	272	if (ret != SR_OK)
	273	break;
	274	}
	275	std_session_send_df_frame_end(sdi);
	276
	277	sr_sw_limits_update_frames_read(&devc->limits, 1);
	278	if (sr_sw_limits_check(&devc->limits))
	279	sr_dev_acquisition_stop(sdi);
	280
	281	return ret;
	282	}
	283
	284	static int recv_poll_data(struct sr_dev_inst sdi, struct sr_serial_dev_inst serial)
	285	{
	286	struct dev_context *devc;
	287	size_t space;
	288	int len;
	289	int ret;
	290
	291	/* Receive data became available. Drain the transport layer. */
	292	devc = sdi->priv;
	293	while (devc->rdlen < TC_POLL_LEN) {
	294	space = sizeof(devc->buf) - devc->rdlen;
	295	len = serial_read_nonblocking(serial,
	296	&devc->buf[devc->rdlen], space);
	297	if (len < 0)
	298	return SR_ERR_IO;
	299	if (len == 0)
	300	return SR_OK;
	301	devc->rdlen += len;
	302	devc->rx_after_tx += len;
	303	}
	304
	305	/*
	306	* TODO Want to (re-)synchronize to the packet stream? The
	307	* 'pac1' string literal would be a perfect match for that.
	308	*/
	309
	310	/* Process packets when their reception has completed. */
	311	while (devc->rdlen >= TC_POLL_LEN) {
	312	ret = handle_poll_data(sdi);
	313	if (ret != SR_OK)
	314	return ret;
	315	devc->rdlen -= TC_POLL_LEN;
	316	if (devc->rdlen)
	317	memmove(devc->buf, &devc->buf[TC_POLL_LEN], devc->rdlen);
	318	}
	319
	320	return SR_OK;
	321	}
	322
	323	SR_PRIV int rdtech_tc_receive_data(int fd, int revents, void *cb_data)
	324	{
	325	struct sr_dev_inst *sdi;
	326	struct dev_context *devc;
	327	struct sr_serial_dev_inst *serial;
	328	int ret;
	329
	330	(void)fd;
	331
	332	if (!(sdi = cb_data))
	333	return TRUE;
	334	if (!(devc = sdi->priv))
	335	return TRUE;
	336
	337	/* Handle availability of receive data. */
	338	serial = sdi->conn;
	339	if (revents == G_IO_IN) {
	340	ret = recv_poll_data(sdi, serial);
	341	if (ret != SR_OK)
	342	sr_dev_acquisition_stop(sdi);
	343	}
	344
	345	/* Check configured acquisition limits. */
	346	if (sr_sw_limits_check(&devc->limits)) {
	347	sr_dev_acquisition_stop(sdi);
	348	return TRUE;
	349	}
	350
	351	/* Periodically retransmit measurement requests. */
	352	(void)rdtech_tc_poll(sdi, FALSE);
	353
	354	return TRUE;
	355	}