Experimental step-up driver for chain of 5630 LEDs.
[tinyboard.git] / projects / step-up / pwmled.c
1 #include <avr/io.h>
2
3 #include "lights.h"
4
5 static uint16_t target;
6 static uint16_t pwm_val;
7 static int16_t err_sum;
8 static unsigned char state;
9 unsigned char mode_changed;
10
11 #define SENSE_MOHM      3000    /* 1 Ohm */
12 /*
13  * Voltage in uV at ADC reading == 1 is 1100/gain/1024
14  * ADC module returns sum of 1 << PWMLED_ADC_SHIFT measurements
15  * Voltage in uV measured is current in mA * sense resistance in mOhm
16  */
17 #define MA_TO_ADC(ma) ((uint16_t) \
18         ((uint32_t)(ma) \
19         * (SENSE_MOHM) \
20         * (1 << (PWMLED_ADC_SHIFT)) \
21         * 1024 \
22         / 1100000))
23
24 static uint16_t adc_max = MA_TO_ADC(30);
25
26 static uint16_t targets[N_PWMLED_MODES] = {
27         MA_TO_ADC( 2),
28         MA_TO_ADC(10),
29         MA_TO_ADC(20),
30 };
31
32 #define ST_DISABLED 0
33 #define ST_OFF      1
34 #define ST_PROBING  2
35 #define ST_ON       3
36 // The above are constructed so that the following work:
37 #define ST_IS_ON(s)     ((s) & 0x02)
38 #define ST_CAN_SET_MODE(s)      ((s) & 0x01)
39
40 void init_pwmled()
41 {
42         pwm_val = 0;
43         err_sum = 0;
44         target = targets[0];
45         state = ST_OFF;
46 }
47
48 void pwmled_set_target(unsigned char mode)
49 {
50         target = targets[mode];
51         mode_changed = 1;
52 }
53
54 void pwmled_on_off(unsigned char mode)
55 {
56         if (!ST_CAN_SET_MODE(state))
57                 return;
58
59         if (mode) {
60                 state = ST_ON;
61                 mode_changed = 1;
62                 need_pwmled_adc = 1;
63                 pwm_set(pwm_val);
64         } else {
65                 state = ST_OFF;
66                 need_pwmled_adc = 0;
67                 pwm_off();
68         }
69 }
70
71 static inline void pwmled_err()
72 {
73         state = ST_DISABLED;
74         pwm_off();
75
76         log_byte(0xF1);
77         log_flush();
78
79         set_error(ERR_PWMLED);
80 }
81
82
83 void pwmled_adc(uint16_t adcval)
84 {
85         int32_t sum;
86         unsigned char shift;
87
88         if (!ST_IS_ON(state))
89                 return;
90
91         // skip the first reading after mode change
92         if (state == ST_ON && mode_changed) {
93                 mode_changed--;
94                 return;
95         }
96
97         if (adcval > adc_max) {
98                 pwmled_err();
99                 return;
100         }
101
102         shift = 5;
103
104         sum = ((int32_t)pwm_val << shift)
105                 + err_sum + target - adcval;
106
107         if (sum < 0)
108                 sum = 0;
109
110         pwm_val = sum >> shift;
111         sum -= pwm_val << shift;
112         err_sum = sum;
113
114         if (pwm_val >= PWM_MAX
115                 || (pwm_val > (2*PWM_MAX/3) && adcval < 0x08)) {
116                 pwmled_err();
117                 need_pwmled_adc = 0;
118                 return;
119         }
120
121         pwm_set(pwm_val);
122 }
123