X-Git-Url: https://sigrok.org/gitweb/?a=blobdiff_plain;f=src%2Fscpi%2Fscpi.c;h=8d24ceea97e29c88de244fae03600a8cf52b6507;hb=c4f0fdab273bcf4c06444a05be296e8d04c6d7a9;hp=0e74b32901f10e21b4a657d2ddebd57dbd401957;hpb=d822f54d523cf3956c081332f0ef9b427926e058;p=libsigrok.git

diff --git a/src/scpi/scpi.c b/src/scpi/scpi.c
index 0e74b329..8d24ceea 100644
--- a/src/scpi/scpi.c
+++ b/src/scpi/scpi.c
@@ -38,6 +38,7 @@ static const char *scpi_vendors[][2] = {
 	{ "Keysight Technologies", "Keysight" },
 	{ "PHILIPS", "Philips" },
 	{ "RIGOL TECHNOLOGIES", "Rigol" },
+	{ "Siglent Technologies", "Siglent" },
 };
 
 /**
@@ -1037,7 +1038,29 @@ SR_PRIV int sr_scpi_get_block(struct sr_scpi_dev_inst *scpi,
 	buf[0] = response->str[1];
 	buf[1] = '\0';
 	ret = sr_atol(buf, &llen);
-	if ((ret != SR_OK) || (llen == 0)) {
+	/*
+	 * The form "#0..." is legal, and does not mean "empty response",
+	 * but means that the number of data bytes is not known (or was
+	 * not communicated) at this time. Instead the block ends at an
+	 * "END MESSAGE" termination sequence. Which translates to active
+	 * EOI while a text line termination is sent (CR or LF, and this
+	 * text line termination is not part of the block's data value).
+	 * Since this kind of #0... response is considered rare, and
+	 * depends on specific support in physical transports underneath
+	 * the SCPI layer, let's flag the condition and bail out with an
+	 * error here, until it's found to be a genuine issue in the field.
+	 *
+	 * The SCPI 1999.0 specification (see page 220 and following in
+	 * the "HCOPy" description) references IEEE 488.2, especially
+	 * section 8.7.9 for DEFINITE LENGTH and section 8.7.10 for
+	 * INDEFINITE LENGTH ARBITRARY BLOCK RESPONSE DATA. The latter
+	 * with a leading "#0" length and a trailing "NL^END" marker.
+	 */
+	if (ret == SR_OK && !llen) {
+		sr_err("unsupported INDEFINITE LENGTH ARBITRARY BLOCK RESPONSE");
+		ret = SR_ERR_NA;
+	}
+	if (ret != SR_OK) {
 		g_mutex_unlock(&scpi->scpi_mutex);
 		g_string_free(response, TRUE);
 		return ret;