I2C slave might stil have something to send when ESP826 starts I2C, thus
keeping the bus stuck.
Happens e.g. when power failure/reset during transmission.
Thanks to work of drmpf there is a solution.
Implemented as separate method so as not to interfere with existing.
Usage:
Wire.begin();
if (Wire.status() != I2C_OK) Serial.writeln("Something wrong with I2C
bus that cannot be recovered. Perform power cycle or search for other
masters on bus.";
The change in 297bb17 enabled RF after deep sleep, even if deep sleep was done with RF_DISABLED option (thanks @vlast3k for pointing this out).
Now we check the value returned by __get_rf_mode, and only call system_phy_set_rfoption if RF_MODE override was provided by user.
- fix return value on timeout
- add optimistic_yield to allow WiFi/network tasks to run
- use ccount instead of micros (which causes an integer division on every call)
Print::printf would allocate 1460 bytes on the stack, which in some cases would overflow the stack. Additionally it didn't handle (rare) cases when vsnprintf needed a buffer longer than 1460 bytes. This change makes default stack-allocated buffer 64 bytes long, and checks the result returned by vsnprintf. If a buffer longer than 64 bytes is needed, it is allocated on the heap.
Calling String::reserve() causes a crash if String object was in invalidated state. Per the comment on the method's declaration in ESP_SSD1306.h, This method was supposed to recover invalidated strings. This change fixes the edge case bug in String::changeBuffer() which is the root cause of the crash exposed from String::reserve().
Following test code was used to reproduce the problem and also to validate the fix:
String result;
while(true){
char c = 'A';
result += c; // the loop will cause malloc() to fail at some point.
if (result.c_str()==0)
{
Serial.println("String INVALIDATED!!!!!");
result.reserve(0); // before fix, this would crash.
Serial.println("Trying to empty....");
result="";
Serial.println("Emptied!!!!");
break;
}
}
This alignment prevents umm_malloc to detect buffer overruns which fall within padding introduced by new/new[]. Allocated memory will be aligned by design of umm_malloc, so we don't need to pad anything here.
Also fixed some formatting/newlines and removed unused header files.
