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lpc176x: Fix wrong inital value at PWM setup 

This fixes a PWM going to full scale output when a initial value != 0 was
given. The output was on 100% until another update occurred.

This change enables the PWM counter before setting the channel values.

Fixes KevinOConnor/klipper#4559

Signed-off-by: Michael Kurz <michi.kurz@gmail.com>
This commit is contained in:
Michael Kurz 2021-08-22 13:58:27 +02:00 committed by KevinOConnor
parent 7f704c4749
commit efbb704522
1 changed files with 7 additions and 8 deletions
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13
src/lpc176x/hard_pwm.c
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@ -61,32 +61,31 @@ gpio_pwm_setup(uint8_t pin, uint32_t cycle_time, uint8_t val) {
enable_pclock(PCLK_PWM1);
}
if (LPC_PWM1->TCR & 1) {
if (LPC_PWM1->TCR & 0x1) {
if (LPC_PWM1->PR != prescaler) {
shutdown("PWM already programmed at different speed");
}
} else {
LPC_PWM1->PCR = 0;
LPC_PWM1->PR = (uint16_t) prescaler;
LPC_PWM1->MCR = 2;
LPC_PWM1->MR0 = MAX_PWM - 1;
LPC_PWM1->LER |= 1 << 0;
LPC_PWM1->TCR = 0x2; // Reset PWM
LPC_PWM1->TCR = 0x2; // Reset PWM TC and PC
LPC_PWM1->MCR = 0x2; // Reset Counter on MR0 match
LPC_PWM1->TCR = 0x8; // Enable PWM mode
LPC_PWM1->TCR |= 0x1; // Enable PWM peripheral
}
if (LPC_PWM1->PCR & (1 << (p->channel + 8))) {
shutdown("PWM output already in use");
}
// Setup channel
struct gpio_pwm channel = {.reg = p->reg, .channel = p->channel};
gpio_pwm_write(channel, val);
// Enable channel
LPC_PWM1->PCR |= (1 << (p->channel + 8));
// Enable PWM peripheral
LPC_PWM1->TCR |= 0x1;
return channel;
}