demo: Mask out logic data for disabled channels in datafeed packets

[libsigrok.git] / src / hardware / demo / api.c

diff --git a/src/hardware/demo/api.c b/src/hardware/demo/api.c
index 92b59fe3a32f07751111e5135b82c408c3fc3c3d..f1a97eb4e5519f8a47f97c0e12290cf239c23b5a 100644 (file)
--- a/src/hardware/demo/api.c
+++ b/src/hardware/demo/api.c
@@ -459,6 +459,8 @@ static int dev_acquisition_start(const struct sr_dev_inst *sdi)
        struct dev_context *devc;
        GSList *l;
        struct sr_channel *ch;
+       int bitpos;
+       uint8_t mask;
        GHashTableIter iter;
        void *value;
 
@@ -468,6 +470,11 @@ static int dev_acquisition_start(const struct sr_dev_inst *sdi)
        devc = sdi->priv;
        devc->sent_samples = 0;
 
+       /*
+        * Determine the numbers of logic and analog channels that are
+        * involved in the acquisition. Determine an offset and a mask to
+        * remove excess logic data content before datafeed submission.
+        */
        devc->enabled_logic_channels = 0;
        devc->enabled_analog_channels = 0;
        for (l = sdi->channels; l; l = l->next) {
@@ -478,12 +485,34 @@ static int dev_acquisition_start(const struct sr_dev_inst *sdi)
                        devc->enabled_analog_channels++;
                        continue;
                }
-               if (ch->type == SR_CHANNEL_LOGIC) {
-                       devc->enabled_logic_channels++;
+               if (ch->type != SR_CHANNEL_LOGIC)
                        continue;
-               }
+               /*
+                * TODO: Need we create a channel map here, such that the
+                * session datafeed packets will have a dense representation
+                * of the enabled channels' data? For example store channels
+                * D3 and D5 in bit positions 0 and 1 respectively, when all
+                * other channels are disabled? The current implementation
+                * generates a sparse layout, might provide data for logic
+                * channels that are disabled while it might suppress data
+                * from enabled channels at the same time.
+                */
+               devc->enabled_logic_channels++;
        }
-
+       devc->first_partial_logic_index = devc->enabled_logic_channels / 8;
+       bitpos = devc->enabled_logic_channels % 8;
+       mask = (1 << bitpos) - 1;
+       devc->first_partial_logic_mask = mask;
+       sr_dbg("DBG: %s(), num logic %zu, partial off %zu, mask 0x%02x",
+               __func__, devc->enabled_logic_channels,
+               devc->first_partial_logic_index,
+               devc->first_partial_logic_mask);
+
+       /*
+        * Have the waveform for analog patterns pre-generated. It's
+        * supposed to be periodic, so the generator just needs to
+        * access the prepared sample data (DDS style).
+        */
        g_hash_table_iter_init(&iter, devc->ch_ag);
        while (g_hash_table_iter_next(&iter, NULL, &value))
                demo_generate_analog_pattern(value, devc->cur_samplerate);