Re: Adding uhd-style tags, to soapy driver?

[Karl]

hi josh,

i'm not a maintainer, but I wanted to comment that i've been looking for features like this for years and the contribution is welcome to see.  most open source projects accept work if it's presented in the ways they're used to.

i've also found the developer of soapy to be relatively responsive and inclusive on github.

On Mon, Oct 18, 2021, 6:42 PM Bailey, Josh <josh@felllight.com> wrote:

Hi all,

The gr-uhd driver, tags samples when center frequency changes and some other events):

https://github.com/gnuradio/gnuradio/blob/8b23f906844c9784c784934ae06dfdfe10d31a1f/gr-uhd/lib/usrp_source_impl.cc#L619

I've been able to make a minimal patch to the soapy driver (see following), that does the same thing for all other SDRs supported by soapy (the patch is for proof of concept/illustrative purposes only - I appreciate that it isn't compatible with the contribution guidelines).

My question - would a suitable patch that provides these tags, be acceptable to the maintainers? I can appreciate that it's possible that there are flow graphs that just happen to use these same tags perhaps for other purposes - perhaps I could then add a flag to make them optional? In any case, the gr-uhd driver appears to always send them, already.

Thanks,

diff --git a/gr-soapy/lib/block_impl.h b/gr-soapy/lib/block_impl.h
index a1e95fdd0..74b2beffe 100644
--- a/gr-soapy/lib/block_impl.h
+++ b/gr-soapy/lib/block_impl.h
@@ -90,6 +90,7 @@ protected:
 public:
     bool start() override;
     bool stop() override;
+    bool _tag_now;
 
     /*** Begin public API implementation ***/
 
diff --git a/gr-soapy/lib/source_impl.cc b/gr-soapy/lib/source_impl.cc
index f76d4437f..93aa06bb2 100644
--- a/gr-soapy/lib/source_impl.cc
+++ b/gr-soapy/lib/source_impl.cc
@@ -47,6 +47,10 @@ source_impl::source_impl(const std::string& device,
 {
 }
 
+static const pmt::pmt_t TIME_KEY = pmt::string_to_symbol("rx_time");
+static const pmt::pmt_t FREQ_KEY = pmt::string_to_symbol("rx_freq");
+static const pmt::pmt_t RATE_KEY = pmt::string_to_symbol("rx_rate");
+
 int source_impl::general_work(int noutput_items,
                               __GR_ATTR_UNUSED gr_vector_int& ninput_items,
                               __GR_ATTR_UNUSED gr_vector_const_void_star& input_items,
@@ -57,6 +61,11 @@ int source_impl::general_work(int noutput_items,
     const long timeout_us = 500000; // 0.5 sec
     int nout = 0;
 
+    std::stringstream str;
+    str << name() << unique_id();
+    pmt::pmt_t _id = pmt::string_to_symbol(str.str());
+    std::time_t time_now = std::time(nullptr);
+
     for (;;) {
 
         // No command handlers while reading
@@ -66,6 +75,25 @@ int source_impl::general_work(int noutput_items,
             result = d_device->readStream(
                 d_stream, output_items.data(), noutput_items, flags, time_ns, timeout_us);
         }
+        if (_tag_now) {
+            _tag_now = false;
+            // create a timestamp pmt for the first sample
+            // TODO: use timestamp from radio hardware, and < 1s granularity?
+            const pmt::pmt_t val =
+                pmt::make_tuple(pmt::from_uint64(time_now),
+                                pmt::from_double(0));
+            // create a tag set for each channel
+            for (size_t i = 0; i < 1; i++) { // TODO: get actual number of channels.
+                this->add_item_tag(i, nitems_written(0), TIME_KEY, val, _id);
+                this->add_item_tag(
+                    i, nitems_written(0), RATE_KEY, pmt::from_double(this->get_sample_rate(i)), _id);
+                this->add_item_tag(i,
+                                   nitems_written(0),
+                                   FREQ_KEY,
+                                   pmt::from_double(this->get_frequency(i)),
+                                   _id);
+            }
+        }
 
         if (result >= 0) {
             nout = result;