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i2c: draft api of "set speed 100k" common

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Only needs the input clock in megahz.
This commit is contained in:
Karl Palsson 2017-03-09 23:13:23 +00:00
parent e3e95adb4d
commit 9930ddd472
1 changed files with 23 additions and 17 deletions
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40
tests/i2c-master/i2c-master.c
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@ -25,29 +25,35 @@ enum sht21_cmd_e {
/* 0xfa, 0x0f to read serial */
};
/* requires clock to be a multiple of 2 ! */
// TODO - plausible to pull up to library, with extraction of 100k param too?
static void i2c_set_speed_100k(uint32_t p, uint32_t clock_megahz)
{
#if defined I2C_SR2
/* target 2Mhz input, so tpresc = 500ns */
int prescaler = clock_megahz / 2 - 1;
i2c_set_prescaler(p, prescaler);
i2c_set_scl_low_period(p, 9); // 5usecs
i2c_set_scl_high_period(p, 7); // 4usecs
i2c_set_data_hold_time(p, 1); // 0.5usecs
i2c_set_data_setup_time(p, 2); // 1.25usecs
#else
i2c_set_clock_frequency(p, clock_megahz);
i2c_set_standard_mode(p);
/* x Mhz / (100kHz * 2) */
i2c_set_ccr(p, clock_megahz * 5);
/* Sm mode, (100kHz) freqMhz + 1 */
i2c_set_trise(p, clock_megahz + 1);
#endif
}
void i2cm_init(void)
{
rcc_periph_clock_enable(hw_details.periph_rcc);
rcc_periph_reset_pulse(hw_details.periph_rst);
// i2c_enable_ack(hw_details.periph); /* NO ACK FOR SHT21! */
//i2c_set_dutycycle(hw_details.periph, I2C_CCR_DUTY_DIV2); /* default, no need to do this really */
#if defined I2C_SR2
i2c_set_clock_frequency(hw_details.periph, hw_details.i2c_clock_megahz);
i2c_set_standard_mode(hw_details.periph);
/* x Mhz / (100kHz * 2) */
i2c_set_ccr(hw_details.periph, hw_details.i2c_clock_megahz * 5);
/* Sm mode, (100kHz) freqMhz + 1 */
i2c_set_trise(hw_details.periph, hw_details.i2c_clock_megahz + 1);
#else
// V2 periph
// See Table 85. Examples of timings settings for f I2CCLK = 48 MHz
i2c_set_prescaler(hw_details.periph, 0xb); // 11 +1 = 2, so 4Mhz input
i2c_set_scl_low_period(hw_details.periph, 0x13);
i2c_set_scl_high_period(hw_details.periph, 0xF);
i2c_set_data_hold_time(hw_details.periph, 0x2);
i2c_set_data_setup_time(hw_details.periph, 0x4);
#endif
i2c_set_speed_100k(hw_details.periph, hw_details.i2c_clock_megahz);
i2c_peripheral_enable(hw_details.periph);
}