As found by @mongozmaki in https://github.com/esp8266/Arduino/pull/6035
With SSO implementation in String, StreamString::write generates wrong
strings under some circumstances. Reason is that String::len() returns
strlen(sso_buf) if SSO=true but with newly written data
(in StreamString::write) the null-termination missing at the time len()
is called.
Furthermore, len() is called twice which is inefficient if SSO=true.
I redid the ESP8266 WString library to enable small string optimization
(SSO) a while back, and think it would be helpful even on the ESP32 with
its higher memory complement.
SSO avoids lots of tiny mallocs() on the heap which cause fragmentation
by using the memory in the class object itself to store the actual
string and only mallocing() for buffers that are larger than what can
fit in thie class object. Modern C++ std::string implementations have
this optimization as well, but since we're using Arduino strings we had
to roll our own.
* add opportunity for more than one retry to _uploadReadByte
* an alternative timeout-based method to making _uploadReadByte more resilient
* move timing variables in the correct scope
* implement and use client.getTimeout instead of hard-coded timeout in _uploadReadByte
* add missing return
* some refactoring to address respecting the timeout in a potentially deadlocked connection
* fix spelling in comment
* address review comments; move impl to cpp file for getTimeout, and remove local variable for currentMillis
* remove redundant cast
* need to check for timeout outside the inner while as well
* update WebUpdate example to print something in unexpected callback condition
* update log_e messages per review comments
The i2c peripheral will hang if a READ request is issued with a zero data length. The peripheral
drops into a continuous timeout interrupt response. The STOP command can not be set out to the I2C
bus. The SLAVE device correctly ACK'd the address byte, with READ bit set, it has control of the SDA
pin. The ESP32 send out the next SCL HIGH pulse but, since the SLAVE is in READ Mode, and the First
bit it is sending happened to be a ZERO, the ESP32 cannot send the STOP. When it releases SDA during
the SCL HIGH, the pin does not change state. The pin stays low because the SLAVE is outputing a LOW!
The ESP32 drops into a perminent WAIT state waiting for SDA to go HIGH (the STOP).
**esp32-hal-i2c.c**
* add databuff length checks to `i2cRead()` and `i2cWrite()`
* Add APB change callbacks and move cpu code to own file
* Properly set esp_timer and FreeRTOS tick dividers
* Improve updated devisors
* No need to update REF_TICK yet
* Add initial handling for UART baud change
* fix uartWriteBuf and uartDetectBaudrate
* trigger callbacks even when APB did not change
* toggle UART ISR on CPU change
* add XTAL freq getter and add cpu freq validation
* Support CPU frequency changes in I2C (#2287)
**esp32-hal-i2c.c**
* add callback for cpu frequency changes
* adjust fifo thresholds based on cpu frequency and i2c bus frequency
* reduce i2c bus frequency if differential is too small
**Wire.h**
* version to 1.1.0
* Implement clock change for the other peripherals
* remove bad CPU clock values from the menu
* Add note to CPU freqs that support WiFi and BT
The I2C hardware has limitations on min and max bus frequency directly related to CPU frequency, bus speed cannot be greater than 1/100 CPU clock, nor less than CPU clock / 8192.
* Add support to HAL for APB frequencies different than 80MHz
* Add support for CPU frequencies in the IDE board menu
* Switch to fast set_config
* Add method to uart so debug can be reassigned after apb frequency switch
* Return real APB frequency
* Fix error in PR #2048: if ::available() is called before ::connect() _rxBuffer is not initialised
* Fixed flash size check and added SPIFFS size check
* Rewriting ESP.getFreeSketchSpace(), moving code from HTTPUpdate.cpp
* Clean warnings when all warning enabled
Not used variables / functions due to debug log
Dual define with different values :
cores\esp32/binary.h
#define B110 6
#define B1000000 64
tools/sdk/include/newlib/sys/termios.h
#define B110 3
#define B1000000 23
Local variable returned in WiFiclient Secure
* change due to deprecated function
* Update with proper variable and label
* Update esp32-hal-i2c.c
* Apply changes requested
* Fix warnings due to #define conflict thanks @atanisoft
* Added baudrate detection to esp32-hal-uart and HardwareSerial
* Solved compiler warning for uartResizeRxBuffer()
* Add unit to header variable name (timeout_ms)
* Reverting accidentally changed files to master
* Add small delay after baudrate detection
#1869 exposed a resource exhaustion issue. The current HAL layer for I2C support is designed to use a shared interrupt, But, during debugging to solve the interrupt overloading condition identified in #1588, and the generation of pr #1717, the interrupt allocation parameters were changed. This change was unnecessary, the code will work successfully with shared interrupts. So, there is no need to assign a private interrupt for each I2C peripheral.
