97 lines
2.9 KiB
C
97 lines
2.9 KiB
C
// Hardware PWM support on lpc176x
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//
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// Copyright (C) 2021 Michael Kurz <michi.kurz@gmail.com>
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//
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// This file may be distributed under the terms of the GNU GPLv3 license.
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#include "autoconf.h" // CONFIG_CLOCK_FREQ
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#include "board/irq.h" // irq_save
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#include "command.h" // shutdown
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#include "gpio.h" // gpio_pwm_write
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#include "internal.h" // GPIO
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#include "sched.h" // sched_shutdown
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#define MAX_PWM 255
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DECL_CONSTANT("PWM_MAX", MAX_PWM);
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struct gpio_pwm_info {
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uint8_t pin, channel, function;
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void *reg;
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};
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static const struct gpio_pwm_info pwm_regs[] = {
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{GPIO(1, 18), 1, 2, (void*)&LPC_PWM1->MR1},
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{GPIO(2, 0), 1, 1, (void*)&LPC_PWM1->MR1},
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{GPIO(1, 20), 2, 2, (void*)&LPC_PWM1->MR2},
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{GPIO(2, 1), 2, 1, (void*)&LPC_PWM1->MR2},
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{GPIO(3, 25), 2, 3, (void*)&LPC_PWM1->MR2},
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{GPIO(1, 21), 3, 2, (void*)&LPC_PWM1->MR3},
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{GPIO(2, 2), 3, 1, (void*)&LPC_PWM1->MR3},
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{GPIO(3, 26), 3, 3, (void*)&LPC_PWM1->MR3},
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{GPIO(1, 23), 4, 2, (void*)&LPC_PWM1->MR4},
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{GPIO(2, 3), 4, 1, (void*)&LPC_PWM1->MR4},
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{GPIO(1, 24), 5, 2, (void*)&LPC_PWM1->MR5},
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{GPIO(2, 4), 5, 1, (void*)&LPC_PWM1->MR5},
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{GPIO(1, 26), 6, 2, (void*)&LPC_PWM1->MR6},
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{GPIO(2, 5), 6, 1, (void*)&LPC_PWM1->MR6}
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};
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struct gpio_pwm
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gpio_pwm_setup(uint8_t pin, uint32_t cycle_time, uint8_t val) {
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// Find pin in pwm_regs table
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const struct gpio_pwm_info* p = pwm_regs;
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for (;; p++) {
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if (p >= &pwm_regs[ARRAY_SIZE(pwm_regs)])
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shutdown("Not a valid PWM pin");
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if (p->pin == pin)
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break;
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}
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// Map cycle_time to pwm clock divisor
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uint32_t clock_div = CONFIG_CLOCK_FREQ / get_pclock_frequency(PCLK_PWM1);
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uint32_t prescaler = (cycle_time / clock_div) / (MAX_PWM - 1);
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if (prescaler > 0) {
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prescaler -= 1;
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}
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gpio_peripheral(p->pin, p->function, 0);
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// Enable clock
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if (!is_enabled_pclock(PCLK_PWM1)) {
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enable_pclock(PCLK_PWM1);
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}
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if (LPC_PWM1->TCR & 0x1) {
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if (LPC_PWM1->PR != prescaler) {
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shutdown("PWM already programmed at different speed");
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}
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} else {
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LPC_PWM1->PCR = 0;
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LPC_PWM1->PR = (uint16_t) prescaler;
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LPC_PWM1->MR0 = MAX_PWM - 1;
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LPC_PWM1->TCR = 0x2; // Reset PWM TC and PC
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LPC_PWM1->MCR = 0x2; // Reset Counter on MR0 match
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LPC_PWM1->TCR = 0x8; // Enable PWM mode
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LPC_PWM1->TCR |= 0x1; // Enable PWM peripheral
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}
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if (LPC_PWM1->PCR & (1 << (p->channel + 8))) {
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shutdown("PWM output already in use");
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}
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// Setup channel
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struct gpio_pwm channel = {.reg = p->reg, .channel = p->channel};
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gpio_pwm_write(channel, val);
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// Enable channel
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LPC_PWM1->PCR |= (1 << (p->channel + 8));
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return channel;
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}
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void
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gpio_pwm_write(struct gpio_pwm g, uint32_t val) {
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*(volatile uint32_t*) g.reg = val;
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LPC_PWM1->LER |= (1 << g.channel);
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}
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