therm Changeset - 9d6570f4456f · protofusion repositories

Changeset - 9d6570f4456f

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cortex-f0

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matthewreed - 9 years ago 2015-12-30 17:28:28

updated pid code to use fixed point math

1 file changed with 11 insertions and 6 deletions:

pid.c

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pid.c

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@@ @@ -11,8 +11,14 @@ void pid_init(pid_state_t* state) @@
 int16_t pid_update(therm_settings_t* set, therm_status_t* status, pid_state_t *state)
+{
   // Convert temperature to fixed point number with 1/10th resolution
   int8_t temp_frac = status->temp_frac > 9 ? status->temp_frac / 10 : status->temp_frac;
   temp_frac = status->temp > 0 ? temp_frac : temp_frac * -1;
   int32_t temp = (status->temp * 10) + temp_frac;
   // Calculate instantaneous error
-  int16_t error = status->setpoint - status->temp; // TODO: Use fixed point fraction
+  int16_t error = status->setpoint * 10 - temp; // TODO: Use fixed point fraction
   // Proportional component
   int32_t p_term = set->val.k_p * error;
@@ @@ -26,7 +32,7 @@ int16_t pid_update(therm_settings_t* set @@
   // it cant help be cold despite its best efforts)
   // not necessary, but this makes windup guard values
   // relative to the current iGain
   int32_t windup_guard_res = set->val.windup_guard / set->val.k_i;
+  int32_t windup_guard_res = (set->val.windup_guard * 10) / set->val.k_i;
   // Calculate integral term with windup guard
   if (state->i_state > windup_guard_res)
@@ @@ -37,13 +43,12 @@ int16_t pid_update(therm_settings_t* set @@
   int32_t i_term = set->val.k_i * state->i_state;
   // Calculate differential term (slope since last iteration)
-  int32_t d_term = (set->val.k_d * (status->temp - state->last_pid_temp));
   int32_t d_term = (set->val.k_d * (temp - state->last_pid_temp));
   // Save temperature for next iteration
   state->last_pid_temp = status->temp;
   state->last_pid_temp_frac = status->temp_frac;
   state->last_pid_temp = temp;
   int16_t result = p_term + i_term - d_term;
+  int16_t result = (p_term + i_term - d_term) / 10;
   // Put out tenths of percent, 0-1000.
   if(result > 1000)

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