kingkevin
/
clapperboard
1
0
Fork 0
Code Issues Pull Requests Projects Releases Wiki Activity

tm1637: set frequency to 50 kHz because of capacitance

This commit is contained in:
King Kévin 2017-05-06 18:32:57 +02:00
parent 183cacf730
commit 663491db61
1 changed files with 2 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
lib/led_tm1637.c
View File

@ -178,7 +178,7 @@ void led_tm1637_setup(void)
timer_reset(TIM(LED_TM1637_TIMER)); // reset timer state
timer_set_mode(TIM(LED_TM1637_TIMER), TIM_CR1_CKD_CK_INT, TIM_CR1_CMS_EDGE, TIM_CR1_DIR_UP); // set timer mode, use undivided timer clock, edge alignment (simple count), and count up
timer_set_prescaler(TIM(LED_TM1637_TIMER), 0); // don't prescale to get most precise timing ( 1/(72E6/1/(2**16))=0.91 ms > 0.5 us )
timer_set_period(TIM(LED_TM1637_TIMER), 500); // set the clock frequency (500 kHz is the maximum per datasheet, but also because of the bit banging implementation)
timer_set_period(TIM(LED_TM1637_TIMER), rcc_ahb_frequency/50000/2); // set the clock frequency to 50 kHz (500 kHz is the maximum per datasheet, but 50 kHz is empirically more stable due to the line capacitance of the multiple displays)
timer_clear_flag(TIM(LED_TM1637_TIMER), TIM_SR_UIF); // clear flag
timer_update_on_overflow(TIM(LED_TM1637_TIMER)); // only use counter overflow as UEV source (use overflow as start time or timeout)
}
@ -205,12 +205,12 @@ static bool led_tm1637_write(const uint8_t* data, uint8_t length)
}
// enable timer for signal generation
gpio_set_mode(GPIO(LED_TM1637_DIO_PORT), GPIO_MODE_OUTPUT_2_MHZ, GPIO_CNF_OUTPUT_PUSHPULL, GPIO(LED_TM1637_DIO_PIN)); // ensure we can output to sent start condition
timer_set_counter(TIM(LED_TM1637_TIMER), 0); // reset timer counter
timer_enable_counter(TIM(LED_TM1637_TIMER)); // enable timer to generate timing
led_tm1637_tick(); // wait to enforce minimum time since last write
// send start condition (DIO then CLK low)
gpio_set_mode(GPIO(LED_TM1637_DIO_PORT), GPIO_MODE_OUTPUT_2_MHZ, GPIO_CNF_OUTPUT_PUSHPULL, GPIO(LED_TM1637_DIO_PIN)); // ensure we can output to sent start condition
gpio_clear(GPIO(LED_TM1637_DIO_PORT), GPIO(LED_TM1637_DIO_PIN)); // put DIO low
led_tm1637_tick(); // wait for next tick
gpio_clear(GPIO(LED_TM1637_CLK_PORT), GPIO(LED_TM1637_CLK_PIN)); // put CLK low