85 lines
1.4 KiB
C
85 lines
1.4 KiB
C
/*
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temp.c
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This file currently reads temp from a MAX6675 on the SPI bus
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*/
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#include "temp.h"
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#include "machine.h"
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#include "pinout.h"
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#include "clock.h"
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uint16_t current_temp = 0;
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uint16_t target_temp = 0;
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int16_t heater_p = 0;
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int16_t heater_i = 0;
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int16_t heater_d = 0;
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int16_t p_factor = 680;
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int16_t i_factor = 18;
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int16_t d_factor = 200;
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#define PID_SCALE 1024
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uint16_t temp_read() {
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uint16_t temp;
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SPCR = MASK(MSTR) | MASK(SPE);
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WRITE(SS, 1);
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SPDR = 0;
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for (;(SPSR & MASK(SPIF)) == 0;);
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temp = SPDR << 8;
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SPDR = 0;
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for (;(SPSR & MASK(SPIF)) == 0;);
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temp |= SPDR;
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if ((temp & 0x8002) == 0) {
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// got "device id"
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if (temp & 4) {
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// thermocouple open
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}
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else {
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current_temp = temp >> 3;
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return current_temp;
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}
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}
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WRITE(SS, 0);
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return 0;
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}
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void temp_set(uint16_t t) {
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target_temp = t;
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}
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void temp_tick() {
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uint16_t last_temp = current_temp;
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temp_read();
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int16_t t_delta = target_temp - current_temp;
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// PID stuff
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heater_p = t_delta;
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heater_i += t_delta;
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// note: D follows temp rather than error so there's no large derivative when the target temperature changes
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heater_d = (current_temp - last_temp);
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int16_t pid_output = ((heater_p * p_factor) + (heater_i * i_factor) + (heater_d * d_factor)) / PID_SCALE;
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#ifdef HEATER_PIN_PWMABLE
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HEATER_PIN_PWMABLE = pid_output
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#else
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if (pid_output > 0) {
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enable_heater();
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}
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else {
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disable_heater();
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}
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#endif
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}
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