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stm32: i2c: Support auto speed configuration 

For both v1 and v2, support automatic calculation of timing registers
for 100khz and 400khz i2c modes.

Based on work by Chuck in
https://github.com/libopencm3/libopencm3/pull/470 for v1
This commit is contained in:
Karl Palsson 2017-03-23 23:56:34 +00:00
parent f3df01f14e
commit 6678da39bd
4 changed files with 87 additions and 0 deletions
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11
include/libopencm3/stm32/common/i2c_common_v1.h
View File

@ -362,6 +362,16 @@ specific memorymap.h header before including this header file.*/
/* --- I2C function prototypes---------------------------------------------- */
/**
* I2C speed modes.
*/
enum i2c_speeds {
i2c_speed_sm_100k,
i2c_speed_fm_400k,
i2c_speed_fmp_1m,
i2c_speed_unknown
};
BEGIN_DECLS
void i2c_reset(uint32_t i2c);
@ -395,6 +405,7 @@ void i2c_disable_dma(uint32_t i2c);
void i2c_set_dma_last_transfer(uint32_t i2c);
void i2c_clear_dma_last_transfer(uint32_t i2c);
void i2c_transfer7(uint32_t i2c, uint8_t addr, uint8_t *w, size_t wn, uint8_t *r, size_t rn);
void i2c_set_speed(uint32_t i2c, enum i2c_speeds speed, uint32_t clock_megahz);
END_DECLS

11
include/libopencm3/stm32/common/i2c_common_v2.h
View File

@ -386,6 +386,16 @@ specific memorymap.h header before including this header file.*/
/* --- I2C function prototypes---------------------------------------------- */
/**
* I2C speed modes.
*/
enum i2c_speeds {
i2c_speed_sm_100k,
i2c_speed_fm_400k,
i2c_speed_fmp_1m,
i2c_speed_unknown
};
BEGIN_DECLS
void i2c_reset(uint32_t i2c);
@ -431,6 +441,7 @@ void i2c_disable_rxdma(uint32_t i2c);
void i2c_enable_txdma(uint32_t i2c);
void i2c_disable_txdma(uint32_t i2c);
void i2c_transfer7(uint32_t i2c, uint8_t addr, uint8_t *w, size_t wn, uint8_t *r, size_t rn);
void i2c_set_speed(uint32_t i2c, enum i2c_speeds speed, uint32_t clock_megahz);
END_DECLS

27
lib/stm32/common/i2c_common_v1.c
View File

@ -539,5 +539,32 @@ void i2c_transfer7(uint32_t i2c, uint8_t addr, uint8_t *w, size_t wn, uint8_t *r
}
}
/**
* Set the i2c communication speed.
* @param i2c peripheral, eg I2C1
* @param speed one of the listed speed modes @ref i2c_speeds
* @param clock_megahz i2c peripheral clock speed in MHz. Usually, rcc_apb1_frequency / 1e6
*/
void i2c_set_speed(uint32_t i2c, enum i2c_speeds speed, uint32_t clock_megahz)
{
i2c_set_clock_frequency(i2c, clock_megahz);
switch(speed) {
case i2c_speed_fm_400k:
i2c_set_fast_mode(i2c);
i2c_set_ccr(i2c, clock_megahz * 5 / 6);
i2c_set_trise(i2c, clock_megahz + 1);
break;
default:
/* fall back to standard mode */
case i2c_speed_sm_100k:
i2c_set_standard_mode(i2c);
/* x Mhz / (100kHz * 2) */
i2c_set_ccr(i2c, clock_megahz * 5);
/* Sm mode, (100kHz) freqMhz + 1 */
i2c_set_trise(i2c, clock_megahz + 1);
break;
}
}
/**@}*/

38
lib/stm32/common/i2c_common_v2.c
View File

@ -436,4 +436,42 @@ void i2c_transfer7(uint32_t i2c, uint8_t addr, uint8_t *w, size_t wn, uint8_t *r
}
/**
* Set the i2c communication speed.
* NOTE: 1MHz mode not yet implemented!
* Min clock speed: 8MHz for FM, 2Mhz for SM,
* @param i2c peripheral, eg I2C1
* @param speed one of the listed speed modes @ref i2c_speeds
* @param clock_megahz i2c peripheral clock speed in MHz. Usually, rcc_apb1_frequency / 1e6
*/
void i2c_set_speed(uint32_t i2c, enum i2c_speeds speed, uint32_t clock_megahz)
{
int prescaler;
switch(speed) {
case i2c_speed_fmp_1m:
/* FIXME - add support for this mode! */
break;
case i2c_speed_fm_400k:
/* target 8Mhz input, so tpresc = 125ns */
prescaler = clock_megahz / 8 - 1;
i2c_set_prescaler(i2c, prescaler);
i2c_set_scl_low_period(i2c, 10-1); // 1250ns
i2c_set_scl_high_period(i2c, 4-1); // 500ns
i2c_set_data_hold_time(i2c, 3); // 375ns
i2c_set_data_setup_time(i2c, 4-1); // 500ns
break;
default:
/* fall back to standard mode */
case i2c_speed_sm_100k:
/* target 4Mhz input, so tpresc = 250ns */
prescaler = (clock_megahz / 4) - 1;
i2c_set_prescaler(i2c, prescaler);
i2c_set_scl_low_period(i2c, 20-1); // 5usecs
i2c_set_scl_high_period(i2c, 16-1); // 4usecs
i2c_set_data_hold_time(i2c, 2); // 0.5usecs
i2c_set_data_setup_time(i2c, 5-1); // 1.25usecs
break;
}
}
/**@}*/