return ret;
}
+/**
+ * Read a variable length non-terminated string (caller specified maximum size).
+ *
+ * @param[in] serial The serial port to read from.
+ * @param[in] count The maximum amount of data to read.
+ * @param[out] buf The buffer to read data into. Must be larger than @a count.
+ *
+ * @return The amount of received data, or negative in case of error.
+ * See @ref SR_ERR and other error codes.
+ *
+ * @internal
+ *
+ * The protocol has no concept of request/response termination. The only
+ * terminating conditions are either the caller's expected maxmimum byte
+ * count, or a period of time without receive data. It's essential to
+ * accept a longer initial period of time before the first receive data
+ * is seen. The supported devices can be very slow to respond.
+ *
+ * The protocol is text based. That's why the 'count' parameter specifies
+ * the expected number of text characters, and does not include the NUL
+ * termination which is not part of the wire protocol but gets added by
+ * the receive routine. The caller provided buffer is expected to have
+ * enough space for the text data and the NUL termination.
+ *
+ * Implementation detail: It's assumed that once receive data was seen,
+ * remaining response data will follow at wire speed. No further delays
+ * are expected beyond bitrate expectations. All normal commands in the
+ * acquisition phase are of fixed length which is known to the caller.
+ * Identification during device scan needs to deal with variable length
+ * data. Quick termination after reception is important there, as is the
+ * larger initial timeout period before receive data is seen.
+ */
SR_PRIV int korad_kaxxxxp_read_chars(struct sr_serial_dev_inst *serial,
- int count, char *buf)
+ size_t count, char *buf)
{
- int ret, received, turns;
+ int timeout_first, timeout_later, timeout;
+ size_t retries_first, retries_later, retries;
+ size_t received;
+ int ret;
+ /* Clear the buffer early, to simplify the receive code path. */
+ memset(buf, 0, count + 1);
+
+ /*
+ * This calculation is aiming for backwards compatibility with
+ * an earlier implementation. An initial timeout is used which
+ * depends on the expected response byte count, and a maximum
+ * iteration count is used for read attempts.
+ *
+ * TODO Consider an absolute initial timeout instead, to reduce
+ * accumulated rounding errors for serial timeout results. The
+ * iteration with a short period is still required for variable
+ * length responses, because otherwise the serial communication
+ * layer would spend the total amount of time waiting for the
+ * remaining bytes, while the device probe code path by design
+ * passes a larger acceptable count than the typical and legal
+ * response would occupy.
+ *
+ * After initial receive data was seen, a shorter timeout is
+ * used which corresponds to a few bytes at wire speed. Idle
+ * periods without receive data longer than this threshold are
+ * taken as the end of the response. This is not compatible to
+ * the previous implementation, but was found to work as well.
+ * And severely reduces the time spent scanning for devices.
+ */
+ timeout_first = serial_timeout(serial, count);
+ retries_first = 100;
+ timeout_later = serial_timeout(serial, 3);
+ retries_later = 1;
+
+ sr_spew("want %zu bytes, timeout/retry: init %d/%zu, later %d/%zu.",
+ count, timeout_first, retries_first,
+ timeout_later, retries_later);
+
+ /*
+ * Run a sequence of read attempts. Try with the larger timeout
+ * and a high retry count until the first receive data became
+ * available. Then continue with a short timeout and small retry
+ * count.
+ *
+ * Failed read is fatal, immediately terminates the read sequence.
+ * A timeout in the initial phase just keeps repeating. A timeout
+ * after receive data was seen regularly terminates the sequence.
+ * Successful reads of non-empty responses keep extending the
+ * read sequence until no more receive data is available.
+ */
received = 0;
- turns = 0;
-
- do {
- if ((ret = serial_read_blocking(serial, buf + received,
- count - received,
- serial_timeout(serial, count))) < 0) {
- sr_err("Error %d reading %d bytes from device.",
+ timeout = timeout_first;
+ retries = retries_first;
+ while (received < count && retries--) {
+ ret = serial_read_blocking(serial,
+ &buf[received], count - received, timeout);
+ if (ret < 0) {
+ sr_err("Error %d reading %zu bytes from device.",
ret, count);
return ret;
}
+ if (ret == 0 && !received)
+ continue;
+ if (ret == 0 && received) {
+ sr_spew("receive timed out, want %zu, received %zu.",
+ count, received);
+ break;
+ }
received += ret;
- turns++;
- } while ((received < count) && (turns < 100));
-
- buf[count] = 0;
-
- sr_spew("Received: '%s'.", buf);
+ timeout = timeout_later;
+ retries = retries_later;
+ }
+ /* TODO Escape non-printables? Seen those with status queries. */
+ sr_dbg("got %zu bytes, received: '%s'.", received, buf);
- return ret;
+ return received;
}
static void give_device_time_to_process(struct dev_context *devc)
sr_dbg("Status: 0x%02x", status_byte);
sr_spew("Status: CH1: constant %s CH2: constant %s. "
- "Tracking would be %s. Device is "
- "%s and %s. Buttons are %s. Output is %s "
- "and extra bit is %s.",
+ "Tracking would be %s and %s. Output is %s. "
+ "OCP is %s, OVP is %s. Device is %s.",
(status_byte & (1 << 0)) ? "voltage" : "current",
(status_byte & (1 << 1)) ? "voltage" : "current",
(status_byte & (1 << 2)) ? "parallel" : "series",
(status_byte & (1 << 3)) ? "tracking" : "independent",
- (status_byte & (1 << 4)) ? "beeping" : "silent",
- (status_byte & (1 << 5)) ? "locked" : "unlocked",
(status_byte & (1 << 6)) ? "enabled" : "disabled",
- (status_byte & (1 << 7)) ? "true" : "false");
+ (status_byte & (1 << 5)) ? "enabled" : "disabled",
+ (status_byte & (1 << 7)) ? "enabled" : "disabled",
+ (status_byte & (1 << 4)) ? "beeping" : "silent");
}
/* Read the sixth byte from ISET? BUG workaround. */
projects / libsigrok.git / blobdiff