AceWire  0.2.0
Unified interface for selecting different I2C implementations on Arduino platforms
Public Member Functions | List of all members
ace_wire::SimpleWireInterface Class Reference

A software I2C implementation for sending LED segment patterns over I2C. More...

#include <SimpleWireInterface.h>

Public Member Functions

 SimpleWireInterface (uint8_t dataPin, uint8_t clockPin, uint8_t delayMicros)
 Constructor. More...
 
void begin () const
 Initialize the clock and data pins. More...
 
void end () const
 Set clock and data pins to INPUT mode.
 
void beginTransmission (uint8_t addr) const
 Send the I2C START condition. More...
 
uint8_t write (uint8_t data) const
 Send the data byte on the data bus, with MSB first as specified by I2C. More...
 
void endTransmission () const
 Send the I2C STOP condition.
 
uint8_t requestFrom (uint8_t addr, uint8_t quantity, bool stop=true)
 Prepare to read bytes by sending I2C START condition.
 
uint8_t read ()
 Read byte. More...
 
void endRequest ()
 End requestFrom() by sending I2C STOP condition if 'stop' is 'true'.
 
 SimpleWireInterface (const SimpleWireInterface &)=default
 
SimpleWireInterfaceoperator= (const SimpleWireInterface &)=default
 

Detailed Description

A software I2C implementation for sending LED segment patterns over I2C.

This has the same API has TwoWireInterface so it can be a drop-in replacement.

The implementation is very similar to SoftTmiInterface because the TM1637 protocol is very similar to I2C. To keep everything simple, all write and read methods are synchronous (i.e. blocking) because interrupts are not used. This means that we can eliminate the send and receive buffers, which saves both flash and static memory.

During writing, beginTransmission() sends the START condition and the I2C address (along with the 'write' bit 0x00) right away. Then each write() call sends each byte immediately. The endTransmission() sends the STOP condition. There is no buffering of the data byte passed into the write() method.

During reading, the requestFrom() sends the START condition and the I2C address (along with the 'read' bit 0x01) right away. Then each call to read() returns the data byte from the slave. Before returning from read(), the master sends a NACK if total number of bytes read is not 'quantity', or an ACK if 'quantity' has just been read. After calling read() 'quantity' times, the client calls endRequest() to send the STOP condition, but only if the 'stop' flag of requestFrom() was set to be true (default).

Definition at line 56 of file SimpleWireInterface.h.

Constructor & Destructor Documentation

◆ SimpleWireInterface()

ace_wire::SimpleWireInterface::SimpleWireInterface ( uint8_t  dataPin,
uint8_t  clockPin,
uint8_t  delayMicros 
)
inlineexplicit

Constructor.

The delayMicroseconds() may not be accurate for small values on some processors (e.g. AVR) . The actual minimum value of delayMicros will depend on the capacitance and resistance on the DATA and CLOCK lines, and the accuracy of the delayMicroseconds() function.

Parameters
dataPinSDA pin
clockPinSCL pin
delayMicrosdelay after each bit transition of SDA or SCL

Definition at line 71 of file SimpleWireInterface.h.

Member Function Documentation

◆ begin()

void ace_wire::SimpleWireInterface::begin ( ) const
inline

Initialize the clock and data pins.

These are open-drain lines, with pull-up resistors. We must not drive them HIGH actively since that could damage the transitor at the other end of the line pulling LOW. Instead, we go into INPUT mode to let the line to HIGH through the pullup resistor, then go to OUTPUT mode only to pull down.

Definition at line 87 of file SimpleWireInterface.h.

◆ beginTransmission()

void ace_wire::SimpleWireInterface::beginTransmission ( uint8_t  addr) const
inline

Send the I2C START condition.

Parameters
addrI2C address of slave device

Definition at line 106 of file SimpleWireInterface.h.

◆ read()

uint8_t ace_wire::SimpleWireInterface::read ( )
inline

Read byte.

After reading 8 bits, an ACK or NACK will be sent by the master to the slave. ACK means the slave will be asked to send more bytes so can hold control of the data line. NACK means no more bytes will be read from the slave and the slave should release the data line.

Definition at line 175 of file SimpleWireInterface.h.

◆ write()

uint8_t ace_wire::SimpleWireInterface::write ( uint8_t  data) const
inline

Send the data byte on the data bus, with MSB first as specified by I2C.

This loop generates slightly asymmetric logic signals because clockLow() lasts for 2*bitDelay(), but clockHigh() lasts for only 1*bitDelay(). This does not seem to cause any problems with the LED modules that I have tested.

Returns
0 means ACK, 1 means NACK.

Definition at line 128 of file SimpleWireInterface.h.


The documentation for this class was generated from the following file: