Moin,
ich nutze zurzeit einen AT32UC3A0512-UES auf einem EVK1100. Ich möchte
eigentlich nur die Spannung die ich per PWM rausgebe (benutze PWM als
Analogausgang) im Betrieb verändern. Dazu habe ich mir folgendes
gebastelt, was auch funktioniert.
1 | static float V = 1.5;
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2 |
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3 | int update_pwm1(void)
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4 | {
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5 | int tmp = (int)((V-3.27)/-0.00308);
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6 |
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7 |
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8 | if(tmp < 1)
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9 | {
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10 | tmp = 1;
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11 | }
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12 | else if(tmp > 1023)
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13 | {
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14 | tmp = 1023;
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15 | }
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16 |
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17 |
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18 | avr32_pwm_channel_t pwm_channel = { .ccnt = 0 }; // One channel config.
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19 |
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20 | pwm_channel.CMR.calg = PWM_MODE_LEFT_ALIGNED; // Channel mode.
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21 | pwm_channel.CMR.cpol = PWM_POLARITY_LOW; // Channel polarity.
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22 | pwm_channel.CMR.cpd = PWM_UPDATE_DUTY; // Not used the first time.
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23 | pwm_channel.CMR.cpre = AVR32_PWM_CPRE_MCK; // Channel prescaler.
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24 | pwm_channel.cdty = 1; // Channel duty cycle, should be < CPRD.
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25 | pwm_channel.cprd = 1024; // Channel period.
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26 | pwm_channel.cupd = tmp;
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27 |
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28 | return pwm_sync_update_channel(1, &pwm_channel);
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29 | }
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30 |
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31 | int main(void)
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32 | {
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33 | // Switch main clock to external oscillator 0 (crystal).
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34 | pm_switch_to_osc0(&AVR32_PM, FOSC0, OSC0_STARTUP);
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35 |
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36 | init_pwm1();
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37 |
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38 | update_pwm1();
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39 |
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40 | while(1);
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41 | }
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Was mich jetzt aber extremst verwirrt ist, dass folgende zwei Varianten
nicht funktionieren und ich absolut keine warum.
Geht nicht:
1 | static volatile float V = 1.5;
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2 |
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3 | int update_pwm1(void)
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4 | {
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5 | int tmp = (int)((V-3.27)/-0.00308);
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6 |
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7 |
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8 | if(tmp < 1)
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9 | {
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10 | tmp = 1;
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11 | }
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12 | else if(tmp > 1023)
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13 | {
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14 | tmp = 1023;
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15 | }
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16 |
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17 |
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18 | avr32_pwm_channel_t pwm_channel = { .ccnt = 0 }; // One channel config.
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19 |
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20 | pwm_channel.CMR.calg = PWM_MODE_LEFT_ALIGNED; // Channel mode.
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21 | pwm_channel.CMR.cpol = PWM_POLARITY_LOW; // Channel polarity.
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22 | pwm_channel.CMR.cpd = PWM_UPDATE_DUTY; // Not used the first time.
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23 | pwm_channel.CMR.cpre = AVR32_PWM_CPRE_MCK; // Channel prescaler.
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24 | pwm_channel.cdty = 1; // Channel duty cycle, should be < CPRD.
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25 | pwm_channel.cprd = 1024; // Channel period.
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26 | pwm_channel.cupd = tmp;
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27 |
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28 | return pwm_sync_update_channel(1, &pwm_channel);
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29 | }
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30 |
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31 | int main(void)
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32 | {
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33 | // Switch main clock to external oscillator 0 (crystal).
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34 | pm_switch_to_osc0(&AVR32_PM, FOSC0, OSC0_STARTUP);
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35 |
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36 | init_pwm1();
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37 |
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38 | update_pwm1();
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39 |
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40 | while(1);
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41 | }
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Geht auch nicht:
1 | //static float V = 1.5;
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2 |
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3 | int update_pwm1(float V)
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4 | {
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5 | int tmp = (int)((V-3.27)/-0.00308);
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6 |
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7 |
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8 | if(tmp < 1)
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9 | {
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10 | tmp = 1;
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11 | }
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12 | else if(tmp > 1023)
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13 | {
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14 | tmp = 1023;
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15 | }
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16 |
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17 |
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18 | avr32_pwm_channel_t pwm_channel = { .ccnt = 0 }; // One channel config.
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19 |
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20 | pwm_channel.CMR.calg = PWM_MODE_LEFT_ALIGNED; // Channel mode.
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21 | pwm_channel.CMR.cpol = PWM_POLARITY_LOW; // Channel polarity.
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22 | pwm_channel.CMR.cpd = PWM_UPDATE_DUTY; // Not used the first time.
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23 | pwm_channel.CMR.cpre = AVR32_PWM_CPRE_MCK; // Channel prescaler.
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24 | pwm_channel.cdty = 1; // Channel duty cycle, should be < CPRD.
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25 | pwm_channel.cprd = 1024; // Channel period.
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26 | pwm_channel.cupd = tmp;
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27 |
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28 | return pwm_sync_update_channel(1, &pwm_channel);
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29 | }
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30 |
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31 | int main(void)
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32 | {
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33 | // Switch main clock to external oscillator 0 (crystal).
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34 | pm_switch_to_osc0(&AVR32_PM, FOSC0, OSC0_STARTUP);
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35 |
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36 | init_pwm1();
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37 |
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38 | update_pwm1(1.5);
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39 |
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40 | while(1);
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41 | }
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Bei den unteren beiden Varianten bleibt die Spannung auf dem Wert, den
sie nach init_pwm1() bereits hat und ändert sich nicht auf ~1,5V.
