From: Alexandru Gagniuc Date: Fri, 2 Nov 2012 15:53:06 +0000 (-0500) Subject: tekpower-dmm: Improve serial detection. X-Git-Tag: dsupstream~544 X-Git-Url: https://sigrok.org/gitaction?a=commitdiff_plain;h=2546b05c801c90a84fb2e6690d8c253c6576b4ab;p=libsigrok.git tekpower-dmm: Improve serial detection. Serial detection was using serial_readline, which stripped carriage return from the packets. This made for a very unreliable detection mechanism. Switch to a timeout-based detection mechanism that parses the data as it comes in. This also allows us to stop parsing once we found our first valid packet. Signed-off-by: Alexandru Gagniuc --- diff --git a/hardware/tekpower-dmm/api.c b/hardware/tekpower-dmm/api.c index 40d48a91..8f78ca51 100644 --- a/hardware/tekpower-dmm/api.c +++ b/hardware/tekpower-dmm/api.c @@ -91,6 +91,78 @@ static int hw_init(void) return SR_OK; } +typedef gboolean (*packet_valid_t)(const uint8_t *buf); + +/** + * Try to find a valid packet in a serial data stream + * + * @param fd File descriptor of the serial port. + * @param buf Buffer containing the bytes to write. + * @param count Size of the buffer. + * @param packet_size Size, in bytes, of a valid packet + * @param is_valid callback that assesses whether the packet is valid or not + * @param timeout_ms the timeout after which, if no packet is detected, to abort + * scanning. + * @param baudrate the baudrate of the serial port. This parameter is not + * critical, but it helps fine tune the serial port polling + * delay + * + * @return SR_OK if a valid packet is found within he given timeout, + * SR_ERR upon failure. + */ +static int serial_stream_detect(struct sr_serial_dev_inst *serial, + uint8_t *buf, size_t *buflen, + const size_t packet_size, + packet_valid_t is_valid, + uint64_t timeout_ms, int baudrate) +{ + uint64_t start; + uint64_t time; + uint64_t byte_delay_us; + size_t ibuf, i; + int len; + const size_t maxlen = *buflen; + + if(maxlen < (packet_size << 1) ) { + sr_err("Buffer size must be at least twice the packet size"); + return SR_ERR; + } + + timeout_ms *= 1000; + /* Assume 8n1 transmission. That is 10 bits for every byte */ + byte_delay_us = 10000000 / baudrate; + start = g_get_monotonic_time(); + + i = ibuf = len = 0; + while (ibuf < maxlen) { + len = serial_read(serial, &buf[ibuf], 1); + if (len > 0) + ibuf+= len; + if ((ibuf - i) >= packet_size) { + /* We have at least a packet's worth of data */ + if (is_valid(&buf[i])) { + time = g_get_monotonic_time()-start; + time /= 1000; + sr_spew("Serial detection took %li ms", time); + *buflen = ibuf; + return SR_OK; + } + /* Not a valid packet; continue searching */ + i++; + } + if (g_get_monotonic_time() - start > timeout_ms) { + /* Timeout */ + sr_warn("Serial detection timeout"); + break; + } + g_usleep(byte_delay_us); + } + + *buflen = ibuf; + return SR_ERR; + +} + static GSList *lcd14_scan(const char *conn, const char *serialcomm) { struct sr_dev_inst *sdi; @@ -99,8 +171,9 @@ static GSList *lcd14_scan(const char *conn, const char *serialcomm) struct sr_probe *probe; struct sr_serial_dev_inst *serial; GSList *devices; - int i, len, retry, good_packets = 0, dropped; - uint8_t buf[128], *b; + int dropped, ret; + size_t len; + uint8_t buf[128]; if (!(serial = sr_serial_dev_inst_new(conn, serialcomm))) return NULL; @@ -111,8 +184,6 @@ static GSList *lcd14_scan(const char *conn, const char *serialcomm) sr_info("Probing port %s readonly.", conn); drvc = di->priv; - b = buf; - retry = 0; devices = NULL; serial_flush(serial); @@ -121,63 +192,51 @@ static GSList *lcd14_scan(const char *conn, const char *serialcomm) * periodically, so the best we can do is check if the packets match * the expected format. */ - while (!devices && retry < 3) { - retry++; - - /* Let's get a bit of data and see if we can find a packet. */ - len = sizeof(buf); - serial_readline(serial, (char **)&b, &len, 500); - if ((len == 0) || (len < FS9721_PACKET_SIZE)) { - /* Not enough data received, is the DMM connected? */ - continue; - } - - /* Let's treat our buffer like a stream, and find any - * valid packets */ - for (i = 0; i < len - FS9721_PACKET_SIZE + 1;) { - if (!sr_fs9721_packet_valid(&buf[i])) { - i++; - continue; - } - good_packets++; - i += FS9721_PACKET_SIZE; - } - /* - * If we dropped more than two packets worth of data, - * something is wrong. - */ - dropped = len - (good_packets * FS9721_PACKET_SIZE); - if (dropped > 2 * FS9721_PACKET_SIZE) - continue; + /* Let's get a bit of data and see if we can find a packet. */ + len = sizeof(buf); - /* Let's see if we have anything good. */ - if (good_packets == 0) - continue; + ret = serial_stream_detect(serial, buf, &len, FS9721_PACKET_SIZE, + sr_fs9721_packet_valid, 1000, 2400); + if (ret != SR_OK) + goto scan_cleanup; - sr_info("Found device on port %s.", conn); + /* + * If we dropped more than two packets worth of data, something is + * wrong. We shouldn't quit however, since the dropped bytes might be + * just zeroes at the beginning of the stream. Those can occur as a + * combination of the nonstandard cable that ships with this device and + * the serial port or USB to serial adapter. + */ + dropped = len - FS9721_PACKET_SIZE; + if (dropped > 2 * FS9721_PACKET_SIZE) { - if (!(sdi = sr_dev_inst_new(0, SR_ST_INACTIVE, "TekPower", - "TP4000ZC", ""))) - return NULL; - if (!(devc = g_try_malloc0(sizeof(struct dev_context)))) { - sr_err("Device context malloc failed."); - return NULL; - } + sr_warn("Had to drop too much data"); + } - devc->serial = serial; + sr_info("Found device on port %s.", conn); - sdi->priv = devc; - sdi->driver = di; - if (!(probe = sr_probe_new(0, SR_PROBE_ANALOG, TRUE, "P1"))) - return NULL; - sdi->probes = g_slist_append(sdi->probes, probe); - drvc->instances = g_slist_append(drvc->instances, sdi); - devices = g_slist_append(devices, sdi); - break; + if (!(sdi = sr_dev_inst_new(0, SR_ST_INACTIVE, "TekPower", + "TP4000ZC", ""))) + goto scan_cleanup; + if (!(devc = g_try_malloc0(sizeof(struct dev_context)))) { + sr_err("Device context malloc failed."); + goto scan_cleanup; } + devc->serial = serial; + + sdi->priv = devc; + sdi->driver = di; + if (!(probe = sr_probe_new(0, SR_PROBE_ANALOG, TRUE, "P1"))) + goto scan_cleanup; + sdi->probes = g_slist_append(sdi->probes, probe); + drvc->instances = g_slist_append(drvc->instances, sdi); + devices = g_slist_append(devices, sdi); + +scan_cleanup: serial_close(serial); + return devices; }