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docs: dac demo comments

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IOsetting 2022-01-27 14:15:03 +08:00
parent cb9a0c5350
commit e9ed4abac5
1 changed files with 4 additions and 2 deletions
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demo/pwm/pwm_dac_voice/main.c
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@ -16,7 +16,8 @@
* Demo: DAC voice output simulation * Demo: DAC voice output simulation
* Board: STC8H3K32 (types with flash size >= 32KB) * Board: STC8H3K32 (types with flash size >= 32KB)
* *
* P1.0 -> Speaker + * P1.0 -> Speaker + // if speaker impedance is less than 8 ohms,
* wire a 5 ohm resistance between P1.0 and speaker
* GND -> Speaker - * GND -> Speaker -
*/ */
#include "fw_hal.h" #include "fw_hal.h"
@ -42,6 +43,7 @@ void PWM_Init()
PWMA_PWM1_SetPortState(HAL_State_ON); PWMA_PWM1_SetPortState(HAL_State_ON);
// Set PWM frequency to 16kHz, Fpwm = SYSCLK / (PWMx_PSCR + 1) / (PWMx_ARR + 1) // Set PWM frequency to 16kHz, Fpwm = SYSCLK / (PWMx_PSCR + 1) / (PWMx_ARR + 1)
// You will hear obvious noise if PWM frequency is less than 12kHz
PWMA_SetPrescaler(8); PWMA_SetPrescaler(8);
// PWM width = Period + 1 (side alignment), or AutoReloadPeriod * 2 (center alignment) // PWM width = Period + 1 (side alignment), or AutoReloadPeriod * 2 (center alignment)
PWMA_SetPeriod(0xFF); PWMA_SetPeriod(0xFF);