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SoftI2CMaster.h
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/* Arduino SoftI2C library.
*
* This is a very fast and very light-weight software I2C-master library
* written in assembler. It is based on Peter Fleury's I2C software
* library: http://homepage.hispeed.ch/peterfleury/avr-software.html
*
*
* This Library 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 Library 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 the Arduino I2cMaster Library. If not, see
* <http://www.gnu.org/licenses/>.
*/
/* In order to use the library, you need to define SDA_PIN, SCL_PIN,
* SDA_PORT and SCL_PORT before including this file. Have a look at
* http://www.arduino.cc/en/Reference/PortManipulation for finding out
* which values to use. For example, if you use digital pin 3 for
* SDA and digital pin 13 for SCL you have to use the following
* definitions:
* #define SDA_PIN 3
* #define SDA_PORT PORTB
* #define SCL_PIN 5
* #define SCL_PORT PORTB
*
* You can also define the following constants (see also below):
* - I2C_CPUFREQ, when changing CPU clock frequency dynamically
* - I2C_FASTMODE = 1 meaning that the I2C bus allows speeds up to 400 kHz
* - I2C_SLOWMODE = 1 meaning that the I2C bus will allow only up to 25 kHz
* - I2C_NOINTERRUPT = 1 in order to prohibit interrupts while
* communicating (see below). This can be useful if you use the library
* for communicationg with SMbus devices, which have timeouts.
* Note, however, that interrupts are disabledfrom issuing a start condition
* until issuing a stop condition. So use this option with care!
* - I2C_TIMEOUT = 0..10000 mssec in order to return from the I2C functions
* in case of a I2C bus lockup (i.e., SCL constantly low). 0 means no timeout
*/
/* Changelog:
* Version 1.1:
* - removed I2C_CLOCK_STRETCHING
* - added I2C_TIMEOUT time in msec (0..10000) until timeout or 0 if no timeout
* - changed i2c_init to return true iff both SDA and SCL are high
* - changed interrupt disabling so that the previous IRQ state is retored
* Version 1.0: basic functionality
*/
#include <avr/io.h>
#include <Arduino.h>
#ifndef _SOFTI2C_H
#define _SOFTI2C_H 1
#if defined (__AVR__)
// Init function. Needs to be called once in the beginning.
// Returns false if SDA or SCL are low, which probably means
// a I2C bus lockup or that the lines are not pulled up.
boolean __attribute__ ((noinline)) i2c_init(void);
// Start transfer function: <addr> is the 8-bit I2C address (including the R/W
// bit).
// Return: true if the slave replies with an "acknowledge", false otherwise
bool __attribute__ ((noinline)) i2c_start(uint8_t addr);
// Similar to start function, but wait for an ACK! Be careful, this can
// result in an infinite loop!
void __attribute__ ((noinline)) i2c_start_wait(uint8_t addr);
// Repeated start function: After having claimed the bus with a start condition,
// you can address another or the same chip again without an intervening
// stop condition.
// Return: true if the slave replies with an "acknowledge", false otherwise
bool __attribute__ ((noinline)) i2c_rep_start(uint8_t addr);
// Issue a stop condition, freeing the bus.
void __attribute__ ((noinline)) i2c_stop(void) asm("ass_i2c_stop");
// Write one byte to the slave chip that had been addressed
// by the previous start call. <value> is the byte to be sent.
// Return: true if the slave replies with an "acknowledge", false otherwise
bool __attribute__ ((noinline)) i2c_write(uint8_t value) asm("ass_i2c_write");
// Read one byte. If <last> is true, we send a NAK after having received
// the byte in order to terminate the read sequence.
uint8_t __attribute__ ((noinline)) i2c_read(bool last);
// You can set I2C_CPUFREQ independently of F_CPU if you
// change the CPU frequency on the fly. If do not define it,
// it will use the value of F_CPU
#ifndef I2C_CPUFREQ
#define I2C_CPUFREQ F_CPU
#endif
// If I2C_FASTMODE is set to 1, then the highest possible frequency below 400kHz
// is selected. Be aware that not all slave chips may be able to deal with that!
#ifndef I2C_FASTMODE
#define I2C_FASTMODE 0
#endif
// If I2C_FASTMODE is not defined or defined to be 0, then you can set
// I2C_SLOWMODE to 1. In this case, the I2C frequency will not be higher
// than 25KHz. This could be useful for problematic buses.
#ifndef I2C_SLOWMODE
#define I2C_SLOWMODE 0
#endif
// if I2C_NOINTERRUPT is 1, then the I2C routines are not interruptable.
// This is most probably only necessary if you are using a 1MHz system clock,
// you are communicating with a SMBus device, and you want to avoid timeouts.
// Be aware that the interrupt bit is enabled after each call. So the
// I2C functions should not be called in interrupt routines or critical regions.
#ifndef I2C_NOINTERRUPT
#define I2C_NOINTERRUPT 0
#endif
// I2C_TIMEOUT can be set to a value between 1 and 10000.
// If it is defined and nonzero, it leads to a timeout if the
// SCL is low longer than I2C_TIMEOUT milliseconds, i.e., max timeout is 10 sec
#ifndef I2C_TIMEOUT
#define I2C_TIMEOUT 0
#else
#if I2C_TIMEOUT > 10000
#error I2C_TIMEOUT is too large
#endif
#endif
#define I2C_TIMEOUT_DELAY_LOOPS (I2C_CPUFREQ/1000UL)*I2C_TIMEOUT/4000UL
#if I2C_TIMEOUT_DELAY_LOOPS < 1
#define I2C_MAX_STRETCH 1
#else
#if I2C_TIMEOUT_DELAY_LOOPS > 60000UL
#define I2C_MAX_STRETCH 60000UL
#else
#define I2C_MAX_STRETCH I2C_TIMEOUT_DELAY_LOOPS
#endif
#endif
#if I2C_FASTMODE
#define I2C_DELAY_COUNTER (((I2C_CPUFREQ/400000L)/2-19)/3)
#else
#if I2C_SLOWMODE
#define I2C_DELAY_COUNTER (((I2C_CPUFREQ/25000L)/2-19)/3)
#else
#define I2C_DELAY_COUNTER (((I2C_CPUFREQ/100000L)/2-19)/3)
#endif
#endif
// Table of I2C bus speed in kbit/sec:
// CPU clock: 1MHz 2MHz 4MHz 8MHz 16MHz 20MHz
// Fast I2C mode 40 80 150 300 400 400
// Standard I2C mode 40 80 100 100 100 100
// Slow I2C mode 25 25 25 25 25 25
// constants for reading & writing
#define I2C_READ 1
#define I2C_WRITE 0
// map the IO register back into the IO address space
#define SDA_DDR (_SFR_IO_ADDR(SDA_PORT) - 1)
#define SCL_DDR (_SFR_IO_ADDR(SCL_PORT) - 1)
#define SDA_OUT _SFR_IO_ADDR(SDA_PORT)
#define SCL_OUT _SFR_IO_ADDR(SCL_PORT)
#define SDA_IN (_SFR_IO_ADDR(SDA_PORT) - 2)
#define SCL_IN (_SFR_IO_ADDR(SCL_PORT) - 2)
#ifndef __tmp_reg__
#define __tmp_reg__ 0
#endif
// Internal delay functions.
void __attribute__ ((noinline)) i2c_delay_half(void) asm("ass_i2c_delay_half");
void __attribute__ ((noinline)) i2c_wait_scl_high(void) asm("ass_i2c_wait_scl_high");
void i2c_delay_half(void)
{ // function call 3 cycles => 3C
#if I2C_DELAY_COUNTER < 1
__asm__ __volatile__ (" ret");
// 7 cycles for call and return
#else
__asm__ __volatile__
(
" ldi r25, %[DELAY] ;load delay constant ;; 4C \n\t"
"_Lidelay: \n\t"
" dec r25 ;decrement counter ;; 4C+xC \n\t"
" brne _Lidelay ;;5C+(x-1)2C+xC\n\t"
" ret ;; 9C+(x-1)2C+xC = 7C+xC"
: : [DELAY] "M" I2C_DELAY_COUNTER : "r25");
// 7 cycles + 3 times x cycles
#endif
}
void i2c_wait_scl_high(void)
{
#if I2C_TIMEOUT <= 0
__asm__ __volatile__
("_Li2c_wait_stretch: \n\t"
" sbis %[SCLIN],%[SCLPIN] ;wait for SCL high \n\t"
" rjmp _Li2c_wait_stretch \n\t"
" cln ;signal: no timeout \n\t"
" ret "
: : [SCLIN] "I" (SCL_IN), [SCLPIN] "I" (SCL_PIN));
#else
__asm__ __volatile__
( " ldi r27, %[HISTRETCH] ;load delay counter \n\t"
" ldi r26, %[LOSTRETCH] \n\t"
"_Lwait_stretch: \n\t"
" clr __tmp_reg__ ;do next loop 255 times \n\t"
"_Lwait_stretch_inner_loop: \n\t"
" rcall _Lcheck_scl_level ;call check function ;; 12C \n\t"
" brpl _Lstretch_done ;done if N=0 ;; +1 = 13C\n\t"
" dec __tmp_reg__ ;dec inner loop counter;; +1 = 14C\n\t"
" brne _Lwait_stretch_inner_loop ;; +2 = 16C\n\t"
" sbiw r26,1 ;dec outer loop counter \n\t"
" brne _Lwait_stretch ;continue with outer loop \n\t"
" sen ;timeout -> set N-bit=1 \n\t"
" rjmp _Lwait_return ;and return with N=1\n\t"
"_Lstretch_done: ;SCL=1 sensed \n\t"
" cln ;OK -> clear N-bit \n\t"
" rjmp _Lwait_return ; and return with N=0 \n\t"
"_Lcheck_scl_level: ;; call = 3C\n\t"
" cln ;; +1C = 4C \n\t"
" sbic %[SCLIN],%[SCLPIN] ;skip if SCL still low ;; +2C = 6C \n\t"
" rjmp _Lscl_high ;; +0C = 6C \n\t"
" sen ;; +1 = 7C\n\t "
"_Lscl_high: "
" nop ;; +1C = 8C \n\t"
" ret ;return N-Bit=1 if low ;; +4 = 12C\n\t"
"_Lwait_return:"
: : [SCLIN] "I" (SCL_IN), [SCLPIN] "I" (SCL_PIN),
[HISTRETCH] "M" (I2C_MAX_STRETCH>>8),
[LOSTRETCH] "M" (I2C_MAX_STRETCH&0xFF)
: "r26", "r27");
#endif
}
boolean i2c_init(void)
{
__asm__ __volatile__
(" cbi %[SDADDR],%[SDAPIN] ;release SDA \n\t"
" cbi %[SCLDDR],%[SCLPIN] ;release SCL \n\t"
" cbi %[SDAOUT],%[SDAPIN] ;clear SDA output value \n\t"
" cbi %[SCLOUT],%[SCLPIN] ;clear SCL output value \n\t"
" clr r24 ;set return value to false \n\t"
" clr r25 ;set return value to false \n\t"
" sbis %[SDAIN],%[SDAPIN] ;check for SDA high\n\t"
" ret ;if low return with false \n\t"
" sbis %[SCLIN],%[SCLPIN] ;check for SCL high \n\t"
" ret ;if low return with false \n\t"
" ldi r24,1 ;set return value to true \n\t"
" ret "
: :
[SCLDDR] "I" (SCL_DDR), [SCLPIN] "I" (SCL_PIN),
[SCLIN] "I" (SCL_IN), [SCLOUT] "I" (SCL_OUT),
[SDADDR] "I" (SDA_DDR), [SDAPIN] "I" (SDA_PIN),
[SDAIN] "I" (SDA_IN), [SDAOUT] "I" (SDA_OUT));
return true;
}
bool i2c_start(uint8_t addr)
{
__asm__ __volatile__
(
#if I2C_NOINTERRUPT
" cli ;clear IRQ bit \n\t"
#endif
" sbis %[SCLIN],%[SCLPIN] ;check for clock stretching slave\n\t"
" rcall ass_i2c_wait_scl_high ;wait until SCL=H\n\t"
" sbi %[SDADDR],%[SDAPIN] ;force SDA low \n\t"
" rcall ass_i2c_delay_half ;wait T/2 \n\t"
" rcall ass_i2c_write ;now write address \n\t"
" ret"
: : [SDADDR] "I" (SDA_DDR), [SDAPIN] "I" (SDA_PIN),
[SCLIN] "I" (SCL_IN),[SCLPIN] "I" (SCL_PIN));
return true; // we never return here!
}
bool i2c_rep_start(uint8_t addr)
{
__asm__ __volatile__
(
#if I2C_NOINTERRUPT
" cli \n\t"
#endif
" sbi %[SCLDDR],%[SCLPIN] ;force SCL low \n\t"
" rcall ass_i2c_delay_half ;delay T/2 \n\t"
" cbi %[SDADDR],%[SDAPIN] ;release SDA \n\t"
" rcall ass_i2c_delay_half ;delay T/2 \n\t"
" cbi %[SCLDDR],%[SCLPIN] ;release SCL \n\t"
" rcall ass_i2c_delay_half ;delay T/2 \n\t"
" sbis %[SCLIN],%[SCLPIN] ;check for clock stretching slave\n\t"
" rcall ass_i2c_wait_scl_high ;wait until SCL=H\n\t"
" sbi %[SDADDR],%[SDAPIN] ;force SDA low \n\t"
" rcall ass_i2c_delay_half ;delay T/2 \n\t"
" rcall ass_i2c_write \n\t"
" ret"
: : [SCLDDR] "I" (SCL_DDR), [SCLPIN] "I" (SCL_PIN),[SCLIN] "I" (SCL_IN),
[SDADDR] "I" (SDA_DDR), [SDAPIN] "I" (SDA_PIN));
return true; // just to fool the compiler
}
void i2c_start_wait(uint8_t addr)
{
__asm__ __volatile__
(
" push r24 ;save original parameter \n\t"
"_Li2c_start_wait1: \n\t"
" pop r24 ;restore original parameter\n\t"
" push r24 ;and save again \n\t"
#if I2C_NOINTERRUPT
" cli ;disable interrupts \n\t"
#endif
" sbis %[SCLIN],%[SCLPIN] ;check for clock stretching slave\n\t"
" rcall ass_i2c_wait_scl_high ;wait until SCL=H\n\t"
" sbi %[SDADDR],%[SDAPIN] ;force SDA low \n\t"
" rcall ass_i2c_delay_half ;delay T/2 \n\t"
" rcall ass_i2c_write ;write address \n\t"
" tst r24 ;if device not busy -> done \n\t"
" brne _Li2c_start_wait_done \n\t"
" rcall ass_i2c_stop ;terminate write & enable IRQ \n\t"
" rjmp _Li2c_start_wait1 ;device busy, poll ack again \n\t"
"_Li2c_start_wait_done: \n\t"
" pop __tmp_reg__ ;pop off orig argument \n\t"
" ret "
: : [SDADDR] "I" (SDA_DDR), [SDAPIN] "I" (SDA_PIN),
[SCLIN] "I" (SCL_IN),[SCLPIN] "I" (SCL_PIN));
}
void i2c_stop(void)
{
__asm__ __volatile__
(
" sbi %[SCLDDR],%[SCLPIN] ;force SCL low \n\t"
" sbi %[SDADDR],%[SDAPIN] ;force SDA low \n\t"
" rcall ass_i2c_delay_half ;T/2 delay \n\t"
" cbi %[SCLDDR],%[SCLPIN] ;release SCL \n\t"
" rcall ass_i2c_delay_half ;T/2 delay \n\t"
" sbis %[SCLIN],%[SCLPIN] ;check for clock stretching slave\n\t"
" rcall ass_i2c_wait_scl_high ;wait until SCL=H\n\t"
" cbi %[SDADDR],%[SDAPIN] ;release SDA \n\t"
" rcall ass_i2c_delay_half \n\t"
#if I2C_NOINTERRUPT
" sei ;enable interrupts again!\n\t"
#endif
: : [SCLDDR] "I" (SCL_DDR), [SCLPIN] "I" (SCL_PIN), [SCLIN] "I" (SCL_IN),
[SDADDR] "I" (SDA_DDR), [SDAPIN] "I" (SDA_PIN));
}
bool i2c_write(uint8_t value)
{
__asm__ __volatile__
(
" sec ;set carry flag \n\t"
" rol r24 ;shift in carry and shift out MSB \n\t"
" rjmp _Li2c_write_first \n\t"
"_Li2c_write_bit:\n\t"
" lsl r24 ;left shift into carry ;; 1C\n\t"
"_Li2c_write_first:\n\t"
" breq _Li2c_get_ack ;jump if TXreg is empty;; +1 = 2C \n\t"
" sbi %[SCLDDR],%[SCLPIN] ;force SCL low ;; +2 = 4C \n\t"
" nop \n\t"
" nop \n\t"
" nop \n\t"
" brcc _Li2c_write_low ;;+1/+2=5/6C\n\t"
" nop ;; +1 = 7C \n\t"
" cbi %[SDADDR],%[SDAPIN] ;release SDA ;; +2 = 9C \n\t"
" rjmp _Li2c_write_high ;; +2 = 11C \n\t"
"_Li2c_write_low: \n\t"
" sbi %[SDADDR],%[SDAPIN] ;force SDA low ;; +2 = 9C \n\t"
" rjmp _Li2c_write_high ;;+2 = 11C \n\t"
"_Li2c_write_high: \n\t"
#if I2C_DELAY_COUNTER >= 1
" rcall ass_i2c_delay_half ;delay T/2 ;;+X = 11C+X\n\t"
#endif
" cbi %[SCLDDR],%[SCLPIN] ;release SCL ;;+2 = 13C+X\n\t"
" cln ;clear N-bit ;;+1 = 14C+X\n\t"
" nop \n\t"
" nop \n\t"
" nop \n\t"
" sbis %[SCLIN],%[SCLPIN] ;check for SCL high ;;+2 = 16C+X\n\t"
" rcall ass_i2c_wait_scl_high \n\t"
" brpl _Ldelay_scl_high ;;+2 = 18C+X\n\t"
"_Li2c_write_return_false: \n\t"
" clr r24 ; return false because of timeout \n\t"
" rjmp _Li2c_write_return \n\t"
"_Ldelay_scl_high: \n\t"
#if I2C_DELAY_COUNTER >= 1
" rcall ass_i2c_delay_half ;delay T/2 ;;+X= 18C+2X\n\t"
#endif
" rjmp _Li2c_write_bit \n\t"
" ;; +2 = 20C +2X for one bit-loop \n\t"
"_Li2c_get_ack: \n\t"
" sbi %[SCLDDR],%[SCLPIN] ;force SCL low ;; +2 = 5C \n\t"
" nop \n\t"
" nop \n\t"
" cbi %[SDADDR],%[SDAPIN] ;release SDA ;;+2 = 7C \n\t"
#if I2C_DELAY_COUNTER >= 1
" rcall ass_i2c_delay_half ;delay T/2 ;; +X = 7C+X \n\t"
#endif
" clr r25 ;; 17C+2X \n\t"
" clr r24 ;return 0 ;; 14C + X \n\t"
" cbi %[SCLDDR],%[SCLPIN] ;release SCL ;; +2 = 9C+X\n\t"
"_Li2c_ack_wait: \n\t"
" cln ; clear N-bit ;; 10C + X\n\t"
" nop \n\t"
" sbis %[SCLIN],%[SCLPIN] ;wait SCL high ;; 12C + X \n\t"
" rcall ass_i2c_wait_scl_high \n\t"
" brmi _Li2c_write_return_false ;; 13C + X \n\t "
" sbis %[SDAIN],%[SDAPIN] ;if SDA hi -> return 0 ;; 15C + X \n\t"
" ldi r24,1 ;return true ;; 16C + X \n\t"
#if I2C_DELAY_COUNTER >= 1
" rcall ass_i2c_delay_half ;delay T/2 ;; 16C + 2X \n\t"
#endif
"_Li2c_write_return: \n\t"
" nop \n\t "
" nop \n\t "
" sbi %[SCLDDR],%[SCLPIN] ;force SCL low so SCL=H is short\n\t"
" ret \n\t"
" ;; + 4 = 17C + 2X for acknowldge bit"
::
[SCLDDR] "I" (SCL_DDR), [SCLPIN] "I" (SCL_PIN), [SCLIN] "I" (SCL_IN),
[SDADDR] "I" (SDA_DDR), [SDAPIN] "I" (SDA_PIN), [SDAIN] "I" (SDA_IN));
return true; // fooling the compiler
}
uint8_t i2c_read(bool last)
{
__asm__ __volatile__
(
" ldi r23,0x01 \n\t"
"_Li2c_read_bit: \n\t"
" sbi %[SCLDDR],%[SCLPIN] ;force SCL low ;; 2C \n\t"
" cbi %[SDADDR],%[SDAPIN] ;release SDA(prev. ACK);; 4C \n\t"
" nop \n\t"
" nop \n\t"
" nop \n\t"
#if I2C_DELAY_COUNTER >= 1
" rcall ass_i2c_delay_half ;delay T/2 ;; 4C+X \n\t"
#endif
" cbi %[SCLDDR],%[SCLPIN] ;release SCL ;; 6C + X \n\t"
#if I2C_DELAY_COUNTER >= 1
" rcall ass_i2c_delay_half ;delay T/2 ;; 6C + 2X \n\t"
#endif
" cln ; clear N-bit ;; 7C + 2X \n\t"
" nop \n\t "
" nop \n\t "
" nop \n\t "
" sbis %[SCLIN], %[SCLPIN] ;check for SCL high ;; 9C +2X \n\t"
" rcall ass_i2c_wait_scl_high \n\t"
" brmi _Li2c_read_return ;return if timeout ;; 10C + 2X\n\t"
" clc ;clear carry flag ;; 11C + 2X\n\t"
" sbic %[SDAIN],%[SDAPIN] ;if SDA is high ;; 11C + 2X\n\t"
" sec ;set carry flag ;; 12C + 2X\n\t"
" rol r23 ;store bit ;; 13C + 2X\n\t"
" brcc _Li2c_read_bit ;while receiv reg not full \n\t"
" ;; 15C + 2X for one bit loop \n\t"
"_Li2c_put_ack: \n\t"
" sbi %[SCLDDR],%[SCLPIN] ;force SCL low ;; 2C \n\t"
" cpi r24,0 ;; 3C \n\t"
" breq _Li2c_put_ack_low ;if (ack=0) ;; 5C \n\t"
" cbi %[SDADDR],%[SDAPIN] ;release SDA \n\t"
" rjmp _Li2c_put_ack_high \n\t"
"_Li2c_put_ack_low: ;else \n\t"
" sbi %[SDADDR],%[SDAPIN] ;force SDA low ;; 7C \n\t"
"_Li2c_put_ack_high: \n\t"
" nop \n\t "
" nop \n\t "
" nop \n\t "
#if I2C_DELAY_COUNTER >= 1
" rcall ass_i2c_delay_half ;delay T/2 ;; 7C + X \n\t"
#endif
" cbi %[SCLDDR],%[SCLPIN] ;release SCL ;; 9C +X \n\t"
" cln ;clear N ;; +1 = 10C\n\t"
" nop \n\t "
" nop \n\t "
" sbis %[SCLIN],%[SCLPIN] ;wait SCL high ;; 12C + X\n\t"
" rcall ass_i2c_wait_scl_high \n\t"
#if I2C_DELAY_COUNTER >= 1
" rcall ass_i2c_delay_half ;delay T/2 ;; 11C + 2X\n\t"
#endif
"_Li2c_read_return: \n\t"
" nop \n\t "
" nop \n\t "
"sbi %[SCLDDR],%[SCLPIN] ;force SCL low so SCL=H is short\n\t"
" mov r24,r23 ;; 12C + 2X \n\t"
" clr r25 ;; 13 C + 2X\n\t"
" ret ;; 17C + X"
::
[SCLDDR] "I" (SCL_DDR), [SCLPIN] "I" (SCL_PIN), [SCLIN] "I" (SCL_IN),
[SDADDR] "I" (SDA_DDR), [SDAPIN] "I" (SDA_PIN), [SDAIN] "I" (SDA_IN)
);
return ' '; // fool the compiler!
}
#else
#error "ONLY SUPPORTED ON AVR PROCESSORS"
#endif // defined (__AVR__)
#endif