Arduino notes

Getting started:

• https://playground.arduino.cc/Learning/CommandLine . . . mentions PlatformIO "ecosystem" and specific Linux ready command line tools for working with Arduino

• https://www.youtube.com/watch?v=qAM2S27FWAI . . . avr-dude and related tools can program Arduino Uno boards

• https://playground.arduino.cc/OpenBSD/CLI . . . Arduino development work on OpenBSD systems

The ATMEGA328P processor used in Arduino Uno boards:

• http://www.microchip.com/wwwproducts/en/ATmega328p . . . the ATMEGA328P processor used in Arduino Uno boards

Specific Arduino projects:

• https://www.hackster.io/niesse/water-level-ultrasonic-sensor-with-lorawan-c2cf55
• https://www.arduino.cc/en/Tutorial/HelloWorld

FreeRTOS port to Arduino:

• https://github.com/feilipu/Arduino_FreeRTOS_Library

Arduino Wire Library

2018-05-21 - Monday, looking at /usr/share/arduino/libraries/Wire/utility/twi.c, routine twi_writeTo() error codes:

177 /*
178  * Function twi_writeTo
179  * Desc     attempts to become twi bus master and write a
180  *          series of bytes to a device on the bus
181  * Input    address: 7bit i2c device address
182  *          data: pointer to byte array
183  *          length: number of bytes in array
184  *          wait: boolean indicating to wait for write or not
185  *          sendStop: boolean indicating whether or not to send a stop at the end
186  * Output   0 .. success
187  *          1 .. length to long for buffer
188  *          2 .. address send, NACK received
189  *          3 .. data send, NACK received
190  *          4 .. other twi error (lost bus arbitration, bus error, ..)
191  */
192 uint8_t twi_writeTo(uint8_t address, uint8_t* data, uint8_t length, uint8_t wait, uint8_t sendStop)
193 {
194   uint8_t i;
195 
196   // ensure data will fit into buffer
197   if(TWI_BUFFER_LENGTH < length){
198     return 1;
199   }
   .
   .
   .

According to the oscilloscope the I2C communications are running at about 192kHz, a little fast. Here is documentation at the Arduino site about setting the I2C clock rate:

• https://www.arduino.cc/en/Reference/WireSetClock . . . Wire.setClock() class method not found on localhost!

Another place where SCL frequency may be set . . .

user@localhost:/usr/share/arduino/libraries/Wire$ grep -nr lock ./*
./Wire.cpp:84:  // perform blocking read into buffer
./Wire.cpp:139:  // transmit buffer (blocking)
./utility/twi.c:85:  SCL Frequency = CPU Clock Frequency / (16 + (2 * TWBR))
./utility/twi.c:467:      // sends ack and stops interface for clock stretching