X-Git-Url: http://sigrok.org/gitweb/?a=blobdiff_plain;f=src%2Foutput%2Fvcd.c;h=3de3dcde37b3a044679ed745e498433c987aa047;hb=17c30d0593ae8db4cd8b185e8bc45a15e4beed5d;hp=43020029ba7ab511d4e0c36437afa85e7c061b19;hpb=adee480c020cf37072f590d4348a737d892e70a6;p=libsigrok.git

diff --git a/src/output/vcd.c b/src/output/vcd.c
index 43020029..3de3dcde 100644
--- a/src/output/vcd.c
+++ b/src/output/vcd.c
@@ -31,7 +31,7 @@ struct context {
 	int num_enabled_channels;
 	uint8_t *prevsample;
 	gboolean header_done;
-	int period;
+	uint64_t period;
 	int *channel_index;
 	uint64_t samplerate;
 	uint64_t samplecount;
@@ -78,6 +78,38 @@ static int init(struct sr_output *o, GHashTable *options)
 	return SR_OK;
 }
 
+/*
+ * VCD can only handle 1/10/100 factors in the s to fs range. Find a
+ * suitable timescale which satisfies this resolution constraint, yet
+ * won't result in excessive overhead.
+ */
+static uint64_t get_timescale_freq(uint64_t samplerate)
+{
+	uint64_t timescale;
+	int max_up_scale;
+
+	/* Go to the next full decade. */
+	timescale = 1;
+	while (timescale < samplerate) {
+		timescale *= 10;
+	}
+
+	/*
+	 * Avoid loss of precision, go up a few more decades when needed.
+	 * For example switch to 10GHz timescale when samplerate is 400MHz.
+	 * Stop after at most factor 100 to not loop endlessly for odd
+	 * samplerates, yet provide good enough accuracy.
+	 */
+	max_up_scale = 2;
+	while (max_up_scale--) {
+		if (timescale / samplerate * samplerate == timescale)
+			break;
+		timescale *= 10;
+	}
+
+	return timescale;
+}
+
 static GString *gen_header(const struct sr_output *o)
 {
 	struct context *ctx;
@@ -96,13 +128,13 @@ static GString *gen_header(const struct sr_output *o)
 	/* timestamp */
 	t = time(NULL);
 	timestamp = g_strdup(ctime(&t));
-	timestamp[strlen(timestamp)-1] = 0;
+	timestamp[strlen(timestamp) - 1] = 0;
 	g_string_printf(header, "$date %s $end\n", timestamp);
 	g_free(timestamp);
 
 	/* generator */
 	g_string_append_printf(header, "$version %s %s $end\n",
-			PACKAGE_NAME, SR_PACKAGE_VERSION_STRING);
+			PACKAGE_NAME, sr_package_version_string_get());
 	g_string_append_printf(header, "$comment\n  Acquisition with "
 			"%d/%d channels", ctx->num_enabled_channels, num_channels);
 
@@ -121,13 +153,7 @@ static GString *gen_header(const struct sr_output *o)
 	g_string_append_printf(header, "\n$end\n");
 
 	/* timescale */
-	/* VCD can only handle 1/10/100 (s - fs), so scale up first */
-	if (ctx->samplerate > SR_MHZ(1))
-		ctx->period = SR_GHZ(1);
-	else if (ctx->samplerate > SR_KHZ(1))
-		ctx->period = SR_MHZ(1);
-	else
-		ctx->period = SR_KHZ(1);
+	ctx->period = get_timescale_freq(ctx->samplerate);
 	frequency_s = sr_period_string(1, ctx->period);
 	g_string_append_printf(header, "$timescale %s $end\n", frequency_s);
 	g_free(frequency_s);
@@ -136,7 +162,7 @@ static GString *gen_header(const struct sr_output *o)
 	g_string_append_printf(header, "$scope module %s $end\n", PACKAGE_NAME);
 
 	/* Wires / channels */
-	for (i = 0, l = o->sdi->channels; l; l = l->next, i++) {
+	for (i = 0, l = o->sdi->channels; l; l = l->next) {
 		ch = l->data;
 		if (ch->type != SR_CHANNEL_LOGIC)
 			continue;
@@ -144,6 +170,7 @@ static GString *gen_header(const struct sr_output *o)
 			continue;
 		g_string_append_printf(header, "$var wire 1 %c %s $end\n",
 				(char)('!' + i), ch->name);
+		i++;
 	}
 
 	g_string_append(header, "$upscope $end\n$enddefinitions $end\n");
@@ -199,7 +226,16 @@ static int receive(const struct sr_output *o, const struct sr_datafeed_packet *p
 			timestamp_written = FALSE;
 
 			for (p = 0; p < ctx->num_enabled_channels; p++) {
-				index = ctx->channel_index[p];
+				/*
+				 * TODO Check whether the mapping from
+				 * data image positions to channel numbers
+				 * is required. Experiments suggest that
+				 * the data image "is dense", and packs
+				 * bits of enabled channels, and leaves no
+				 * room for positions of disabled channels.
+				 */
+				/* index = ctx->channel_index[p]; */
+				index = p;
 
 				curbit = ((unsigned)sample[index / 8]
 						>> (index % 8)) & 1;
@@ -260,7 +296,7 @@ static int cleanup(struct sr_output *o)
 struct sr_output_module output_vcd = {
 	.id = "vcd",
 	.name = "VCD",
-	.desc = "Value Change Dump",
+	.desc = "Value Change Dump data",
 	.exts = (const char*[]){"vcd", NULL},
 	.flags = 0,
 	.options = NULL,