visomat-data-downloader: document why code is 4 bytes in decode_datetime()

[visomat-utils.git] / README

diff --git a/README b/README
index 9cc74be..f8a07e9 100644 (file)
--- a/README
+++ b/README
@@ -21,7 +21,7 @@ communication anyways.
 
 Each data packet starts with the STX control character, and ends with ETX.
 
-There are at least two kind of packets: requests and responses.
+There are at least two kinds of packets: requests and responses.
 
 A request can be used to send command codes to the device.
 
@@ -68,3 +68,19 @@ The structure can be better visualized when split in fields:
   440601 1319 0 114 063 066
   100101 1400 0 114 070 071
   130312 1145 0 121 080 072
+
+When the number of records is 0, there is a dummy byte at the end of the user
+memory block, e.g.:
+
+  M1001M20115110321300134097083
+
+The structure is:
+
+  M
+  1
+  00
+  1   # dummy byte, present only when the previous field is 00
+  M
+  2
+  01
+  151103 2130 0 134 097 083