Firmware2/Marlin/twibus.h

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/*
* Marlin 3D Printer Firmware
* Copyright (C) 2016 MarlinFirmware [https://github.com/MarlinFirmware/Marlin]
*
* Based on Sprinter and grbl.
* Copyright (C) 2011 Camiel Gubbels / Erik van der Zalm
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
*/
#ifndef TWIBUS_H
#define TWIBUS_H
/**
* TWIBUS class
*
* This class implements a wrapper around the two wire (I2C) bus, it allows
* Marlin to send and request data from any slave device on the bus. This is
* an experimental feature and it's inner workings as well as public facing
* interface are prune to change in the future.
*
* The two main consumers of this class are M155 and M156, where M155 allows
* Marlin to send a I2C packet to a device (please be aware that no repeated
* starts are possible), this can be done in caching method by calling multiple
* times M155 B<byte-1 value in base 10> or a one liner M155, have a look at
* the gcode_M155() function for more information. M156 allows Marlin to
* request data from a device, the received data is then relayed into the serial
* line for host interpretation.
*
*/
class TWIBus {
private:
/**
* @brief Timeout value in milliseconds
* @details For blocking operations this constant value will set the max
* amount of time Marlin will keep waiting for a reply. Useful is something
* goes wrong on the bus and the SDA/SCL lines are held up by another device.
*/
const int timeout = 5;
/**
* @brief Target device address
* @description This stores, until the buffer is flushed, the target device
* address, take not we do follow Arduino 7bit addressing.
*/
uint8_t addr = 0;
/**
* @brief Number of bytes on buffer
* @description This var holds the total number of bytes on our buffer
* waiting to be flushed to the bus.
*/
uint8_t buffer_s = 0;
/**
* @brief Internal buffer
* @details This is a fixed buffer, TWI command cannot be longer than this
*/
char buffer[30];
public:
/**
* @brief Class constructor
* @details Initialized the TWI bus and clears the buffer
*/
TWIBus();
/**
* @brief Reset the buffer
* @details Brings the internal buffer to a known-empty state
*/
void reset();
/**
* @brief Send the buffer data to the bus
* @details Flushed the buffer into the bus targeting the cached slave device
* address.
*/
void send();
/**
* @brief Add one byte to the buffer
* @details Adds the byte to the buffer in a sequential way, if buffer is full
* the request is silently ignored.
*
* @param c a data byte
*/
void addbyte(char c);
/**
* @brief Sets the target slave address
* @details The target slave address is stored so it can be later used when
* the complete packet needs to be sent over the bus.
*
* @param addr 7-bit integer address
*/
void address(uint8_t addr);
/**
* @brief Request data from slave device
* @details Requests data from a slave device, when the data is received it will
* be relayed to the serial line using a parser-friendly formatting.
*
* @param bytes the number of bytes to request
*/
void reqbytes(uint8_t bytes);
};
#endif //TWIBUS_H