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Diffstat (limited to 'docs/esp8266/general.rst')
| -rw-r--r-- | docs/esp8266/general.rst | 25 |
1 files changed, 24 insertions, 1 deletions
diff --git a/docs/esp8266/general.rst b/docs/esp8266/general.rst index 47df80d7ba..e23acb469b 100644 --- a/docs/esp8266/general.rst +++ b/docs/esp8266/general.rst @@ -116,9 +116,32 @@ Real-time clock RTC in ESP8266 has very bad accuracy, drift may be seconds per minute. As a workaround, to measure short enough intervals you can use ``utime.time()``, etc. functions, and for wall clock time, synchronize from -the net using included ``ntpdate.py`` module. +the net using included ``ntptime.py`` module. Due to limitations of the ESP8266 chip the internal real-time clock (RTC) will overflow every 7:45h. If a long-term working RTC time is required then ``time()`` or ``localtime()`` must be called at least once within 7 hours. MicroPython will then handle the overflow. + +Sockets and WiFi buffers overflow +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Socket instances remain active until they are explicitly closed. This has two +consequences. Firstly they occupy RAM, so an application which opens sockets +without closing them may eventually run out of memory. Secondly not properly +closed socket can cause the low-level part of the vendor WiFi stack to emit +``Lmac`` errors. This occurs if data comes in for a socket and is not +processed in a timely manner. This can overflow the WiFi stack input queue +and lead to a deadlock. The only recovery is by a hard reset. + +The above may also happen after an application terminates and quits to the REPL +for any reason including an exception. Subsequent arrival of data provokes the +failure with the above error message repeatedly issued. So, sockets should be +closed in any case, regardless whether an application terminates successfully +or by an exeption, for example using try/finally:: + + sock = socket(...) + try: + # Use sock + finally: + sock.close() |