Is this library compatible with ARM-based boards or/and Atmega32u4-based boards?

[q2dg]

Thanks

[AngeloStavrow]

I'll answer here based on my current testing with an Arduino Due: it presently is not compatible with ARM, as it includes util/delay.h on line 22 of SoftI2CMaster.cpp, which is part of the AVR core.

I've forked and am working on a fix.

[q2dg]

Thanks!!

[AngeloStavrow]

Okay, this goes a lot deeper than just swapping _delay_us() for delayMicroseconds() depending on the microcontroller architecture. Maybe @todbot has some pointers.

I started with some #ifdefs at the top of the .cpp file to start:

#ifdef __AVR__                                          // Target AVR boards
    #include <util/delay.h>
#endif
#if defined (__SAM3X8E__)                               // Target Arduino Due
    #define _delay_us(us) delayMicroseconds(us)
#endif

This macro clears up the issue with the delay. But when I include the library in an near-empty sketch, I get the following compile errors:

Arduino: 1.6.5 (Windows 8.1), Board: "Arduino Due (Programming Port)"

C:\Users\username\Documents\Arduino\libraries\SoftI2CMaster\SoftI2CMaster.cpp: In member function 'void SoftI2CMaster::setPins(uint8_t, uint8_t, uint8_t)':
C:\Users\username\Documents\Arduino\libraries\SoftI2CMaster\SoftI2CMaster.cpp:99:10: error: invalid conversion from 'Pio*' to 'uint8_t {aka unsigned char}' [-fpermissive]
     port = digitalPinToPort(sclPin);
          ^
In file included from C:\Users\username\AppData\Roaming\Arduino15\packages\arduino\hardware\sam\1.6.4\cores\arduino/Arduino.h:189:0,
                 from C:\Users\username\Documents\Arduino\libraries\SoftI2CMaster\SoftI2CMaster.cpp:15:
C:\Users\username\AppData\Roaming\Arduino15\packages\arduino\hardware\sam\1.6.4\variants\arduino_due_x/variant.h:65:44: error: base operand of '->' is not a pointer
 #define portOutputRegister(port)   ( &(port->PIO_ODSR) )
                                            ^
C:\Users\username\Documents\Arduino\libraries\SoftI2CMaster\SoftI2CMaster.cpp:100:20: note: in expansion of macro 'portOutputRegister'
     _sclPortReg  = portOutputRegister(port);
                    ^
C:\Users\username\Documents\Arduino\libraries\SoftI2CMaster\SoftI2CMaster.cpp:101:41: error: 'portModeRegister' was not declared in this scope
     _sclDirReg   = portModeRegister(port);
                                         ^
C:\Users\username\Documents\Arduino\libraries\SoftI2CMaster\SoftI2CMaster.cpp:103:10: error: invalid conversion from 'Pio*' to 'uint8_t {aka unsigned char}' [-fpermissive]
     port = digitalPinToPort(sdaPin);
          ^
In file included from C:\Users\username\AppData\Roaming\Arduino15\packages\arduino\hardware\sam\1.6.4\cores\arduino/Arduino.h:189:0,
                 from C:\Users\username\Documents\Arduino\libraries\SoftI2CMaster\SoftI2CMaster.cpp:15:
C:\Users\username\AppData\Roaming\Arduino15\packages\arduino\hardware\sam\1.6.4\variants\arduino_due_x/variant.h:65:44: error: base operand of '->' is not a pointer
 #define portOutputRegister(port)   ( &(port->PIO_ODSR) )
                                            ^
C:\Users\username\Documents\Arduino\libraries\SoftI2CMaster\SoftI2CMaster.cpp:104:20: note: in expansion of macro 'portOutputRegister'
     _sdaPortReg  = portOutputRegister(port);
                    ^
C:\Users\username\Documents\Arduino\libraries\SoftI2CMaster\SoftI2CMaster.cpp: In member function 'uint8_t SoftI2CMaster::i2c_readbit()':
C:\Users\username\AppData\Roaming\Arduino15\packages\arduino\hardware\sam\1.6.4\variants\arduino_due_x/variant.h:62:65: error: invalid conversion from 'Pio*' to 'uint8_t {aka unsigned char}' [-fpermissive]
 #define digitalPinToPort(P)        ( g_APinDescription[P].pPort )
                                                                 ^
C:\Users\username\Documents\Arduino\libraries\SoftI2CMaster\SoftI2CMaster.cpp:212:20: note: in expansion of macro 'digitalPinToPort'
     uint8_t port = digitalPinToPort(_sdaPin);
                    ^
C:\Users\username\AppData\Roaming\Arduino15\packages\arduino\hardware\sam\1.6.4\variants\arduino_due_x/variant.h:66:44: error: base operand of '->' is not a pointer
 #define portInputRegister(port)    ( &(port->PIO_PDSR) )
                                            ^
C:\Users\username\Documents\Arduino\libraries\SoftI2CMaster\SoftI2CMaster.cpp:213:32: note: in expansion of macro 'portInputRegister'
     volatile uint8_t* pinReg = portInputRegister(port);
                                ^
Error compiling.

So it looks like now the trouble is in the differences between direct port manipulation for AVR boards and the SAM/ARM-based Arduino Due.

[todbot]

Hi
For Arduino Due (ARM SAM), I think you may be able to convert the definesi2c_scl_lo() and i2c_scl_hi() and similar to the equivalent of Arduino commands.
e.g.

#define i2c_scl_release()  pinMode(_sclPin,INPUT); 
#define i2c_sda_release()  pinMode(_sdaPin,INPUT); 
#define i2c_scl_lo()  digitalWrite(_sclPin,LOW);
#define i2c_sda_lo()  digitalWrite(_sdaPin,LOW);
#define i2c_scl_hi()  if(usePullups) pinMode(_sclPin,INPUT_PULLUP); else digitalWrite(_sclPin,HIGH);
#define i2c_sda_hi()  if(usePullups) pinMode(_sdaPin,INPUT_PULLUP); else digitalWrite(_sdaPin,HIGH);

The Due/ARM part of the code would then also have a different setPins() method that would just save the value of sclPin and sdaPin and ignore the other mask & port attributes.

Unfortunately I don't have a Due to try this on. I do have a Teensy3 which is a similar architecture. If I have time tonight I'll try it out. (I'd also like to try this change out on AVR-based Arduinos. When I wrote this, digitalWrite() was much slower than it is now on AVR and INPUT_PULLUP didn't exist. digitalWrite() might work now on AVR)

[AngeloStavrow]

Thanks for the suggestion!

I have access to both Uno and Due so I'm happy to help test.

I'm working a bit on this too.

[AngeloStavrow]

Okay, I'm a little bit stuck with porting the i2c_readbit() function. It seems to me that this could simply be replaced with

i2c_sda_hi();
    i2c_scl_hi();
    _delay_us(i2cbitdelay);

    uint8_t c = digitalRead(_sdaPin);

    i2c_scl_lo();
    _delay_us(i2cbitdelay);

    return c;

but while that (obviously) resolves the compile error (complaints about digitalPinToPort()), it doesn't seem to work.

FWIW, I replaced setPins() per the above comment with

void SoftI2CMaster::setPins(uint8_t sclPin, uint8_t sdaPin, uint8_t pullups)
{
    uint8_t port;

    usePullups = pullups;

    _sclPin = sclPin;
    _sdaPin = sdaPin;
}

I have very likely overlooked something obvious—any tips for this, @todbot?

[ekiuser]

Hi!
I'm also trying to use this "SoftI2CMaster" with my m0 Pro Arduino (SAMD21 micro, ARM based).
Shoul I download the equivalent library for ARM? If yes which library is this and where can I download it?

[ekiuser]

I mean the equivalent "avr" library for ARM

[dm99]

Works for me, successfully read values from some pressure sensor with DUE . My changes:

void SoftI2CMaster::i2c_init(void) {
pinMode(_sclPin, OUTPUT);
pinMode(_sdaPin, OUTPUT);
i2c_sda_hi();
i2c_scl_hi();
delayMicroseconds(i2cbitdelay);
}

uint8_t SoftI2CMaster::i2c_readbit(void) {
i2c_sda_hi();
i2c_scl_hi();
delayMicroseconds(i2cbitdelay);
pinMode(_sdaPin, INPUT);
uint8_t c = digitalRead(_sdaPin);
i2c_scl_lo();
delayMicroseconds(i2cbitdelay);
pinMode(_sdaPin, OUTPUT);
return c;
}

and todbot function definitions.

[HansHint]

Hello @dm99 ,
great that you could get it running on an arduino Due. I tried the same, considering your post, but i still get some errors, the first one is identical with the post of @AngeloStavrow .
I did the following:

first i added in SoftI2CMaster.cpp:

#ifdef __AVR__                                          // Target AVR boards
    #include <util/delay.h>
#endif
#if defined (__SAM3X8E__)                               // Target Arduino Due
    #define _delay_us(us) delayMicroseconds(us)
#endif

then i added @todbot s function definitions:

#define i2c_scl_release()  pinMode(_sclPin,INPUT); 
#define i2c_sda_release()  pinMode(_sdaPin,INPUT); 
#define i2c_scl_lo()  digitalWrite(_sclPin,LOW);
#define i2c_sda_lo()  digitalWrite(_sdaPin,LOW);
#define i2c_scl_hi()  if(usePullups) pinMode(_sclPin,INPUT_PULLUP); else digitalWrite(_sclPin,HIGH);
#define i2c_sda_hi()  if(usePullups) pinMode(_sdaPin,INPUT_PULLUP); else digitalWrite(_sdaPin,HIGH);

(replacing the following code:)

#define i2c_scl_release()                 \
    *_sclDirReg     &=~ _sclBitMask
#define i2c_sda_release()                 \
    *_sdaDirReg     &=~ _sdaBitMask

// sets SCL low and drives output
#define i2c_scl_lo()                                 \
                     *_sclPortReg  &=~ _sclBitMask;  \
                     *_sclDirReg   |=  _sclBitMask; 

// sets SDA low and drives output
#define i2c_sda_lo()                                 \
                     *_sdaPortReg  &=~ _sdaBitMask;  \
                     *_sdaDirReg   |=  _sdaBitMask;  

// set SCL high and to input (releases pin) (i.e. change to input,turnon pullup)
#define i2c_scl_hi()                                 \
                     *_sclDirReg   &=~ _sclBitMask;  \
    if(usePullups) { *_sclPortReg  |=  _sclBitMask; } 

// set SDA high and to input (releases pin) (i.e. change to input,turnon pullup)
#define i2c_sda_hi()                                 \
                     *_sdaDirReg   &=~ _sdaBitMask;  \
    if(usePullups) { *_sdaPortReg  |=  _sdaBitMask; }

then i inserted your changes:

void SoftI2CMaster::i2c_init(void) {
pinMode(_sclPin, OUTPUT);
pinMode(_sdaPin, OUTPUT);
i2c_sda_hi();
i2c_scl_hi();
delayMicroseconds(i2cbitdelay);
}

uint8_t SoftI2CMaster::i2c_readbit(void) {
i2c_sda_hi();
i2c_scl_hi();
delayMicroseconds(i2cbitdelay);
pinMode(_sdaPin, INPUT);
uint8_t c = digitalRead(_sdaPin);
i2c_scl_lo();
delayMicroseconds(i2cbitdelay);
pinMode(_sdaPin, OUTPUT);
return c;
}

(replacing this section:)

uint8_t SoftI2CMaster::i2c_readbit(void)
{
    i2c_sda_hi();
    i2c_scl_hi();
    _delay_us(i2cbitdelay);

    uint8_t port = digitalPinToPort(_sdaPin);
    volatile uint8_t* pinReg = portInputRegister(port);
    uint8_t c = *pinReg;  // I2C_PIN;

    i2c_scl_lo();
    _delay_us(i2cbitdelay);

    return ( c & _sdaBitMask) ? 1 : 0;
}

// Inits bitbanging port, must be called before using the functions below
//
void SoftI2CMaster::i2c_init(void)
{
    //I2C_PORT &=~ (_BV( I2C_SDA ) | _BV( I2C_SCL ));
    //*_sclPortReg &=~ (_sdaBitMask | _sclBitMask);
    i2c_sda_hi();
    i2c_scl_hi();

    _delay_us(i2cbitdelay);
}

in my sketch i also replaced

"#include <Wire.h>"

with

"#include "SoftI2CMaster.h""

and in my Wire-functions i replaced all "Wire." with "i2c.", e.g. "Wire.write(val)" with "i2c.write(val);"

did i miss something? or did i do something wrong?

it would be a great help for me and certainly fore some other people if you could post a whole working example, including also the changes in the relating library-files.

thanks a lot, dm99!

[dm99]

This is working SoftI2CMaster (.cpp) and arduino file for reading an Keller pressure transmitter and put the result on LCD.

SoftI2CMaster.pdf
Keller.pdf

[HansHint]

Thanks a lot, dm99! Is it working in SAM-chip or on Mega?

[dm99]

Arduino Due

[HansHint]

Thank you- i need to connect a Humidity Sensor. I' ll try it this weekend...

[HansHint]

Hi again dm99,
i tried your files, but i got a compiler error:
SoftI2CMaster.cpp:30: error: expected constructor, destructor, or type conversion before '(' token
digitalWrite(_sclPin,HIGH);

did you change anything else? I compiled with Arduino IDE 1.6.6. it should work, shouldnt it?

[dm99]

My is 1.6.11, but it should works. It looks like arduino.h isn't included for same reason.
I didn't change anything else. Checked with modification time of entire arduino and arduino library tree.

[HansHint]

i think, arduino.h is included, because if i comment it out with "//" , there are much more errors. is it possible that it has something to do with the formatting in the pdf-format? can you maybe post your complete code in raw code format in this forum? what about the SoftI2CMaster.h -file? is it original or also with some changes? thanks again!

[HansHint]

hi @dm99,
sorry to bother you again, but you seem to be the only person in the whole (google-) world, who did a working Software-I2C-connection on an Arduino Due.
finally i got the softI2c compiling without errors. but i still am not sure how to use it correctly. i tried to use it with a Sparkfun Humidity sensor on my Due. I am using the Sparkfun Library for that purpose. What i could manage was using it on both genuine I2C buses of the Due. Therefore i only had to change "Wire." into "Wire1" in the SparkfunHTU21D.cpp . But i am not sure how to change that Sparkfun-Library to get a working version combined with the Software - I2c- bus. I tried to change "Wire." into "i2c." but i get error messages like: "SparkFunHTU21D.cpp:40:3: error: 'i2c' was not declared in this scope
i2c.begin();"
@dm99, would you think you can help me get it running? you are my big hope, because you got working the other sensor, too... i am also willing to pay a little bit for that job...

[dm99]

try this (.cpp)
SparkFunHTU21D.pdf

[HansHint]

Hi @dm99
Thank You so much, we are very close now, because i finally get some values from the sensor:-)
but i still have some question:
i had to change the delay times slightly, because otherwise the sensor gives back 999 for humidity and temp., also the read_user_register(void) doesnt work, so i commented it out.
the reason why i ask again is: the values are slightly different from the same sensor coming via the standard i2c bus: humidity is 5% too low and temp is 5 deg. too high, and i am not sure where this comes from? i saw that you used a different .cpp file than the one i linked. or did you make all the changes, e.g. the converting from raw to real humidity?
i have two theories now: maybe there is some "mathematical" issue , (maybe coming from the different file versions ?) ore its a hardware issue - maybe the Soft-I2C-transmission heats up the sensor? what would you say? and thank you once again - your file was a huge step forward for me!
ps: maybe you could post the code directly as code in the comment window? i hade some problems with line breakings copying from the pdf...

[HansHint]

Ok, finally i cleaned up the code a little bit and added the suggestions of @dm99. There are no compile errors left. there was a different spelling of the "read_user_register()" function, so i renamed it in the file SparkFunHTU21D.h. in attached files you can see my working code. only issue: the slight differences between the measured values, either with hardware or software i2C...

SparkFunHTU21D_Software_I2C.zip

[HansHint]

Ok, everything works fine with the code. There was another reason for the wrong values, not the I2C-Bus: i had a reference Hygrometer, which lost its calibration- the values are identical on both kinds of I2C:-) Thank you once again, @dm99. So the zip-file in my previous posting works fine, if anybody else wants to use it;-)