2 * Copyright © 2012 Keith Packard <keithp@keithp.com>
4 * This program is free software; you can redistribute it and/or modify
5 * it under the terms of the GNU General Public License as published by
6 * the Free Software Foundation; version 2 of the License.
8 * This program is distributed in the hope that it will be useful, but
9 * WITHOUT ANY WARRANTY; without even the implied warranty of
10 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
11 * General Public License for more details.
13 * You should have received a copy of the GNU General Public License along
14 * with this program; if not, write to the Free Software Foundation, Inc.,
15 * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
22 #include <ao_ms5607.h>
26 #include <ao_mpu6000.h>
30 #include <ao_hmc5883.h>
39 struct ao_ms5607_sample ms5607_raw;
40 struct ao_ms5607_value ms5607_cooked;
43 struct ao_mpu6000_sample mpu6000;
46 struct ao_hmc5883_sample hmc5883;
50 #define ao_data_ring_next(n) (((n) + 1) & (AO_DATA_RING - 1))
51 #define ao_data_ring_prev(n) (((n) - 1) & (AO_DATA_RING - 1))
53 extern volatile __xdata struct ao_data ao_data_ring[AO_DATA_RING];
54 extern volatile __data uint8_t ao_data_head;
58 typedef int32_t pres_t;
59 typedef int32_t alt_t;
61 #define ao_data_pres_cook(packet) ao_ms5607_convert(&packet->ms5607_raw, &packet->ms5607_cooked)
63 #define ao_data_pres(packet) ((packet)->ms5607_cooked.pres)
64 #define ao_data_temp(packet) ((packet)->ms5607_cooked.temp)
66 #define pres_to_altitude(p) ao_pa_to_altitude(p)
68 #else /* HAS_MS5607 */
70 typedef int16_t pres_t;
71 typedef int16_t alt_t;
73 #define ao_data_pres(packet) ((packet)->adc.pres)
74 #define ao_data_temp(packet) ((packet)->adc.temp)
75 #define pres_to_altitude(p) ao_pres_to_altitude(p)
76 #define ao_data_pres_cook(p)
78 #endif /* else HAS_MS5607 */
81 * Need a few macros to pull data from the sensors:
83 * ao_data_accel_sample - pull raw sensor and convert to normalized values
84 * ao_data_accel - pull normalized value (lives in the same memory)
85 * ao_data_set_accel - store normalized value back in the sensor location
86 * ao_data_accel_invert - flip rocket ends for positive acceleration
89 #if HAS_MPU6000 && !HAS_HIGHG_ACCEL
91 typedef int16_t accel_t;
93 /* MPU6000 is hooked up so that positive y is positive acceleration */
94 #define ao_data_accel(packet) ((packet)->mpu6000.accel_y)
95 #define ao_data_accel_cook(packet) (-(packet)->mpu6000.accel_y)
96 #define ao_data_set_accel(packet, accel) ((packet)->mpu6000.accel_y = (accel))
97 #define ao_data_accel_invert(a) (-(a))
99 #else /* HAS_MPU6000 && !HAS_HIGHG_ACCEL */
101 typedef int16_t accel_t;
102 #define ao_data_accel(packet) ((packet)->adc.accel)
103 #define ao_data_set_accel(packet, a) ((packet)->adc.accel = (a))
104 #define ao_data_accel_invert(a) (0x7fff -(a))
107 * Ok, the math here is a bit tricky.
109 * ao_sample_accel: ADC output for acceleration
110 * ao_accel_ref: ADC output for the 5V reference.
111 * ao_cook_accel: Corrected acceleration value
112 * Vcc: 3.3V supply to the CC1111
113 * Vac: 5V supply to the accelerometer
114 * accel: input voltage to accelerometer ADC pin
115 * ref: input voltage to 5V reference ADC pin
118 * Measured acceleration is ratiometric to Vcc:
120 * ao_sample_accel accel
121 * ------------ = -----
124 * Measured 5v reference is also ratiometric to Vcc:
127 * ------------ = -----
131 * ao_accel_ref = 32767 * (ref / Vcc)
133 * Acceleration is measured ratiometric to the 5V supply,
134 * so what we want is:
136 * ao_cook_accel accel
137 * ------------- = -----
145 * ao_sample_accel 32767
146 * = ------------ * ------------
149 * Multiply through by 32767:
151 * ao_sample_accel * 32767
152 * ao_cook_accel = --------------------
155 * Now, the tricky part. Getting this to compile efficiently
156 * and keeping all of the values in-range.
158 * First off, we need to use a shift of 16 instead of * 32767 as SDCC
159 * does the obvious optimizations for byte-granularity shifts:
161 * ao_cook_accel = (ao_sample_accel << 16) / ao_accel_ref
163 * Next, lets check our input ranges:
165 * 0 <= ao_sample_accel <= 0x7fff (singled ended ADC conversion)
166 * 0x7000 <= ao_accel_ref <= 0x7fff (the 5V ref value is close to 0x7fff)
168 * Plugging in our input ranges, we get an output range of 0 - 0x12490,
169 * which is 17 bits. That won't work. If we take the accel ref and shift
170 * by a bit, we'll change its range:
172 * 0xe000 <= ao_accel_ref<<1 <= 0xfffe
174 * ao_cook_accel = (ao_sample_accel << 16) / (ao_accel_ref << 1)
176 * Now the output range is 0 - 0x9248, which nicely fits in 16 bits. It
177 * is, however, one bit too large for our signed computations. So, we
178 * take the result and shift that by a bit:
180 * ao_cook_accel = ((ao_sample_accel << 16) / (ao_accel_ref << 1)) >> 1
182 * This finally creates an output range of 0 - 0x4924. As the ADC only
183 * provides 11 bits of data, we haven't actually lost any precision,
184 * just dropped a bit of noise off the low end.
189 #define ao_data_accel_cook(packet) \
190 ((uint16_t) ((((uint32_t) (packet)->adc.accel << 16) / ((packet)->adc.accel_ref << 1))) >> 1)
194 #define ao_data_accel_cook(packet) ((packet)->adc.accel)
196 #endif /* HAS_ACCEL_REF */
198 #endif /* else some other accel sensor */
200 #endif /* _AO_DATA_H_ */