doc(bkgpslog-plan):Closed TODO item

[EVA-2020-02.git] / exec / bkgpslog-plan.org

diff --git a/exec/bkgpslog-plan.org b/exec/bkgpslog-plan.org
index da2370480f66ea57868de63f228bd2a69bd49ae2..47154eb893c07bfb01d8fe044121048378705e28 100644 (file)
--- a/exec/bkgpslog-plan.org
+++ b/exec/bkgpslog-plan.org
@@ -27,11 +27,37 @@ when a new session is started.
 is checked and its status as a valid tar file is validated. This was
 done using a new function ~checkMakeTar~.
 ** DONE Add VERSION if output tar deleted between writes
+
    CLOSED: [2020-07-02 Thu 20:22]
 2020-07-02T20:21Z; bktei> Added bkgpslog-specified function
 magicWriteVersion() to be called whenever a new time-stamped ~VERSION~
 file needs to be generated and appended to the output tar file
 ~PATHOUT_TAR~.
+** DONE Rewrite buffer loop to reduce lag between gpspipe runs
+   CLOSED: [2020-07-03 Fri 20:57]
+2020-07-03T17:10Z; bktei> As is, there is still a 5-6 second lag
+between when ~gpspipe~ times out at the end of a buffer round and when
+~gpspipe~ is called by the subsequent buffer round. I believe this can
+be reduced by moving variable manipulations inside the
+asynchronously-executed magicWriteBuffer() function. Ideally, the
+while loop should look like:
+
+#+BEGIN_EXAMPLE
+while( $SECONDS < $SCRIPT_TTL); do
+    gpspipe-r > "$DIR_TMP"/buffer.nmea
+    writeBuffer &
+done
+#+END_EXAMPLE
+2020-07-03T20:56Z; bktei> I simplified it futher to something like
+this:
+#+BEGIN_EXAMPLE
+while( $SECONDS < $SCRIPT_TTL); do
+    writeBuffer &
+    sleep $SCRIPT_TTL
+done
+#+END_EXAMPLE
+Raspberry Pi Zero W shows approximately 71ms of drift per buffer round
+with 10s buffer.
 * bkgpslog narrative
 ** Initialize environment
 *** Init variables