Hallo Forum,
ich würde gerne ein digitales I2C-Potentiometer an's Laufen bringen und verfüge leider weder über C++-, noch Python-Kenntnisse. Bash-Skripte kriege ich meist noch irgendwie hin. Doch das Umschreiben vorhandener Codebeispiele bereitet mir arge Probleme.
Konkret versuche ich es gerade mit C++ nach diesem Beispiel (http://blog.stibrany.com/?p=9). Der Typ betreibt den MCP4561. Ich möchte hingegen den MCP4551 ansteuern. Er besitzt, im Unterschied zum MCP4561, keinen Speicher.
Leider hat der Blogger eine Closed-Source I2C-library verwendet und empfiehlt zum Nachmachen diese hier. Dafür muss sein Programm lediglich "ein bißchen" umgeschrieben werden.
OK, ich hab das jetzt versucht, doch weiß ich weder, ob meine Änderungen alle richtig sind, noch wie das Ding überhaupt gestartet wird. Da wird ja kreuz und quer verlinkt und "included", sodass ich nichtmal weiß, wo überhaupt das Testprogramm hinkäme. Der soll einfach nur den Poti rauf- und runterdrehen - und das in einer Endlosschleife. Feinheiten kann ich mir dann ja überlegen.
Meine bisherigen Codeschnipsel sehen so aus:
mcp4551.h:
#ifndef MCP4551_H_
#define MCP4551_H_
typedef unsigned char uint8_t;
typedef unsigned short uint16_t;
#define MCP4551_ADDR 0b01011100
// Register memory address
#define MCP4551_WIPER0 0x00
#define MCP4551_WIPER1 0x01
#define MCP4551_WIPER0_NV 0x02
#define MCP4551_TCON 0x04
#define MCP4551_STATUS 0x05
// Command Operation
#define MCP4551_WRITE 0x00
#define MCP4551_READ (0x03 << 2)
#define MCP4551_INC (0x01 << 2)
#define MCP4551_DEC (0x02 << 2)
// TCON Register Bits
#define MCP4551_TCON_GCEN (1 << 8) /* General Call Enable bit*/
#define MCP4551_TCON_R0HW (1 << 3) /* Resistor 0 hardware configuration control bit*/
#define MCP4551_TCON_R0A (1 << 2) /* Resistor 0 terminal A connect control bit*/
#define MCP4551_TCON_R0W (1 << 1) /* Resistor 0 wiper connect control bit*/
#define MCP4551_TCON_R0B (1 << 0) /* Resistor 0 terminal B connect control bit */
void mcp4551_incrementWiper0();
void mcp4551_decrementWiper0();
uint8_t mcp4551_selfCheck();
void mcp4551_enableAllTerminals();
void mcp4551_setWiper0(uint16_t val);
uint16_t mcp4551_Read(uint8_t memAddr);
uint8_t mcp4551_Write(uint8_t memAddr,uint8_t cmd, uint16_t data);
void mcp4551_init();
#endif /* MCP4551_H_ */
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mcp4551.cpp (erste Zeile aus dem Original muss bestimmt weg, zweite Zeile ist von mir und soll auf die alternative I2C-Bibliothek verweisen):
#include <xlib/core/i2c.h>
#include "./i2cmaster/i2cmaster.h"
#include "mcp4551.h"
I2c i2c;
void mcp4551_init()
{
#i2c.InitMaster(i2c0,100000);
i2c_init();
}
uint8_t mcp4551_Write(uint8_t memAddr,uint8_t cmd, uint16_t data)
{
uint8_t cmdHasData = false;
uint8_t setVal = 0;
if ( (cmd != MCP4551_INC) && (cmd != MCP4551_DEC))
cmdHasData = true;
setVal = ((memAddr << 4) & 0xF0); // 4b Memory address
setVal |= cmd; // 2b Command operation
setVal |= (((data&0x01FF) >> 8) & 0x03); // 2b Data
i2c_write(setVal);
if (cmdHasData) {
i2c_write(data & 0x00FF);
}
// args: I2C address, number of bytes to receive
i2c_start_wait(MCP4551_ADDR+0);
_delay_ms(10);
if (cmdHasData){ // and so we can check whether it has accepted the setting
uint8_t set_reading = mcp4551_Read(memAddr);
if (set_reading == data)
{
return 0;
}
return 1;
}
return 0;
}
uint16_t mcp4551_Read(uint8_t memAddr)
{
uint8_t cmd = (memAddr << 4) | MCP4551_READ;
uint16_t data;
i2c_write(cmd);
// args: I2C address, number of bytes to receive
i2c_start_wait(MCP4551_ADDR+2);
data = (i2c.Read() << 8);
data |= i2c.Read();
return data;
}
uint8_t mcp4551_selfCheck()
{
return (mcp4551_Read(MCP4551_STATUS) == 0x01F0);
}
void mcp4551_enableAllTerminals()
{
uint8_t config = 0;
config = MCP4551_TCON_R0HW;
config |= MCP4551_TCON_R0A;
config |= MCP4551_TCON_R0W;
config |= MCP4551_TCON_R0B;
mcp4551_Write(MCP4551_TCON, MCP4551_WRITE, config);
}
uint8_t mcp4551_setWiper0(uint16_t val)
{
uint8_t error = 0;
// Sanity check. Datasheet says there are 257 steps(values) available
val = val % 257;
error = mcp4551_Write(MCP4551_WIPER0, MCP4551_WRITE, val);
/* We also save this value to EEPROM, so after reset,
this value is set */
error |= mcp4551_Write(MCP4551_WIPER0_NV, MCP4551_WRITE, val);
return error;
}
void mcp4551_incrementWiper0()
{
mcp4551_Write(MCP4551_WIPER0, MCP4551_INC,0);
}
void mcp4551_decrementWiper0()
{
mcp4551_Write(MCP4551_WIPER0, MCP4551_DEC,0);
}
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main.cpp:
#include <avr/io.h>
#include <stdlib.h>
#include "mcp4551.h"
uint8_t initDigitalPotentiometer();
void setDigitalPotentiometerResistance(uint16_t val);
int main()
{
uint8_t potentiometerValue = 0;
EnableInterrupts();
initDigitalPotentiometer();
while (1)
{
setDigitalPotentiometerResistance(potentiometerValue);
potentiometerValue = (potentiometerValue + 1) % 256;
_delay_ms(1000);
}
}
uint8_t initDigitalPotentiometer()
{
mcp4551_init();
if ( mcp4551_selfCheck() == false)
return 0;
mcp4551_enableAllTerminals();
return 1;
}
void setDigitalPotentiometerResistance(uint16_t val)
{
mcp4551_setWiper0(val);
}
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Die I2C-Bibliothek habe ich nicht verändert, deshalb nur die Header-Datei, wo man die Funktionsnamen sieht (die wichen von den aufgerufenen Funktionen im Original-Programm ab, weil ja eine kommerzielle Bibliothek verwendet wurde). Den Rest der Opnsource-Bibliothek hänge ich als Zip-Datei an, falls jemand daran interessiert ist:
#ifndef _I2CMASTER_H
#define _I2CMASTER_H
/*************************************************************************
* Title: C include file for the I2C master interface
* (i2cmaster.S or twimaster.c)
* Author: Peter Fleury <pfleury@gmx.ch>
* File: $Id: i2cmaster.h,v 1.12 2015/09/16 09:27:58 peter Exp $
* Software: AVR-GCC 4.x
* Target: any AVR device
* Usage: see Doxygen manual
**************************************************************************/
/**
@file
@defgroup pfleury_ic2master I2C Master library
@code #include <i2cmaster.h> @endcode
@brief I2C (TWI) Master Software Library
Basic routines for communicating with I2C slave devices. This single master
implementation is limited to one bus master on the I2C bus.
This I2c library is implemented as a compact assembler software implementation of the I2C protocol
which runs on any AVR (i2cmaster.S) and as a TWI hardware interface for all AVR with built-in TWI hardware (twimaster.c).
Since the API for these two implementations is exactly the same, an application can be linked either against the
software I2C implementation or the hardware I2C implementation.
Use 4.7k pull-up resistor on the SDA and SCL pin.
Adapt the SCL and SDA port and pin definitions and eventually the delay routine in the module
i2cmaster.S to your target when using the software I2C implementation !
Adjust the CPU clock frequence F_CPU in twimaster.c or in the Makfile when using the TWI hardware implementaion.
@note
The module i2cmaster.S is based on the Atmel Application Note AVR300, corrected and adapted
to GNU assembler and AVR-GCC C call interface.
Replaced the incorrect quarter period delays found in AVR300 with
half period delays.
@author Peter Fleury pfleury@gmx.ch http://tinyurl.com/peterfleury
@copyright (C) 2015 Peter Fleury, GNU General Public License Version 3
@par API Usage Example
The following code shows typical usage of this library, see example test_i2cmaster.c
@code
#include <i2cmaster.h>
#define Dev24C02 0xA2 // device address of EEPROM 24C02, see datasheet
int main(void)
{
unsigned char ret;
i2c_init(); // initialize I2C library
// write 0x75 to EEPROM address 5 (Byte Write)
i2c_start_wait(Dev24C02+I2C_WRITE); // set device address and write mode
i2c_write(0x05); // write address = 5
i2c_write(0x75); // write value 0x75 to EEPROM
i2c_stop(); // set stop conditon = release bus
// read previously written value back from EEPROM address 5
i2c_start_wait(Dev24C02+I2C_WRITE); // set device address and write mode
i2c_write(0x05); // write address = 5
i2c_rep_start(Dev24C02+I2C_READ); // set device address and read mode
ret = i2c_readNak(); // read one byte from EEPROM
i2c_stop();
for(;;);
}
@endcode
*/
/**@{*/
#if (__GNUC__ * 100 + __GNUC_MINOR__) < 304
#error "This library requires AVR-GCC 3.4 or later, update to newer AVR-GCC compiler !"
#endif
#include <avr/io.h>
/** defines the data direction (reading from I2C device) in i2c_start(),i2c_rep_start() */
#define I2C_READ 1
/** defines the data direction (writing to I2C device) in i2c_start(),i2c_rep_start() */
#define I2C_WRITE 0
/**
@brief initialize the I2C master interace. Need to be called only once
@return none
*/
extern void i2c_init(void);
/**
@brief Terminates the data transfer and releases the I2C bus
@return none
*/
extern void i2c_stop(void);
/**
@brief Issues a start condition and sends address and transfer direction
@param addr address and transfer direction of I2C device
@retval 0 device accessible
@retval 1 failed to access device
*/
extern unsigned char i2c_start(unsigned char addr);
/**
@brief Issues a repeated start condition and sends address and transfer direction
@param addr address and transfer direction of I2C device
@retval 0 device accessible
@retval 1 failed to access device
*/
extern unsigned char i2c_rep_start(unsigned char addr);
/**
@brief Issues a start condition and sends address and transfer direction
If device is busy, use ack polling to wait until device ready
@param addr address and transfer direction of I2C device
@return none
*/
extern void i2c_start_wait(unsigned char addr);
/**
@brief Send one byte to I2C device
@param data byte to be transfered
@retval 0 write successful
@retval 1 write failed
*/
extern unsigned char i2c_write(unsigned char data);
/**
@brief read one byte from the I2C device, request more data from device
@return byte read from I2C device
*/
extern unsigned char i2c_readAck(void);
/**
@brief read one byte from the I2C device, read is followed by a stop condition
@return byte read from I2C device
*/
extern unsigned char i2c_readNak(void);
/**
@brief read one byte from the I2C device
Implemented as a macro, which calls either @ref i2c_readAck or @ref i2c_readNak
@param ack 1 send ack, request more data from device<br>
0 send nak, read is followed by a stop condition
@return byte read from I2C device
*/
extern unsigned char i2c_read(unsigned char ack);
#define i2c_read(ack) (ack) ? i2c_readAck() : i2c_readNak();
/**@}*/
#endif
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Da ich im Detail nur Bahnhof verstehe, hoffe ich mir kann jemand beim Zusammenfügen der Teile helfen. Ich will einfach nur diesem Poti Befehle senden können.