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Diffstat (limited to 'src/core/ao_data.h')
| -rw-r--r-- | src/core/ao_data.h | 191 |
1 files changed, 191 insertions, 0 deletions
diff --git a/src/core/ao_data.h b/src/core/ao_data.h new file mode 100644 index 00000000..d28730a8 --- /dev/null +++ b/src/core/ao_data.h @@ -0,0 +1,191 @@ +/* + * Copyright © 2012 Keith Packard <keithp@keithp.com> + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; version 2 of the License. + * + * This program is distributed in the hope that it will be useful, but + * WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + * General Public License for more details. + * + * You should have received a copy of the GNU General Public License along + * with this program; if not, write to the Free Software Foundation, Inc., + * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA. + */ + +#ifndef _AO_DATA_H_ +#define _AO_DATA_H_ + +#if HAS_MS5607 +#include <ao_ms5607.h> +#endif + +#if HAS_MPU6000 +#include <ao_mpu6000.h> +#endif + +struct ao_data { + uint16_t tick; +#if HAS_ADC + struct ao_adc adc; +#endif +#if HAS_ACCEL_REF + uint16_t accel_ref; +#endif +#if HAS_MS5607 + struct ao_ms5607_sample ms5607; +#endif +#if HAS_MPU6000 + struct ao_mpu6000_sample mpu6000; +#endif +}; + +#define ao_data_ring_next(n) (((n) + 1) & (AO_DATA_RING - 1)) +#define ao_data_ring_prev(n) (((n) - 1) & (AO_DATA_RING - 1)) + +extern volatile __xdata struct ao_data ao_data_ring[AO_DATA_RING]; +extern volatile __data uint8_t ao_data_head; + +#if HAS_MS5607 + +typedef int32_t pres_t; +typedef int32_t alt_t; + +static inline pres_t ao_data_pres(struct ao_data *packet) +{ + struct ao_ms5607_value value; + + ao_ms5607_convert(&packet->ms5607, &value); + return value.pres; +} + +#define pres_to_altitude(p) ao_pa_to_altitude(p) + +#else + +typedef int16_t pres_t; +typedef int16_t alt_t; + +#define ao_data_pres(packet) ((packet)->adc.pres) +#define pres_to_altitude(p) ao_pres_to_altitude(p) + +#endif + +/* + * Need a few macros to pull data from the sensors: + * + * ao_data_accel_sample - pull raw sensor and convert to normalized values + * ao_data_accel - pull normalized value (lives in the same memory) + * ao_data_set_accel - store normalized value back in the sensor location + * ao_data_accel_invert - flip rocket ends for positive acceleration + */ + +#if HAS_MPU6000 + +typedef int16_t accel_t; + +/* MPU6000 is hooked up so that positive y is positive acceleration */ +#define ao_data_accel(packet) ((packet)->mpu6000.accel_y) +#define ao_data_accel_sample(packet) (-ao_data_accel(packet)) +#define ao_data_set_accel(packet, accel) ((packet)->mpu6000.accel_y = (accel)) +#define ao_data_accel_invert(a) (-(a)) + +#else + +typedef int16_t accel_t; +#define ao_data_accel(packet) ((packet)->adc.accel) +#define ao_data_set_accel(packet, accel) ((packet)->adc.accel = (accel)) +#define ao_data_accel_invert(a) (0x7fff -(a)) + +/* + * Ok, the math here is a bit tricky. + * + * ao_sample_accel: ADC output for acceleration + * ao_accel_ref: ADC output for the 5V reference. + * ao_cook_accel: Corrected acceleration value + * Vcc: 3.3V supply to the CC1111 + * Vac: 5V supply to the accelerometer + * accel: input voltage to accelerometer ADC pin + * ref: input voltage to 5V reference ADC pin + * + * + * Measured acceleration is ratiometric to Vcc: + * + * ao_sample_accel accel + * ------------ = ----- + * 32767 Vcc + * + * Measured 5v reference is also ratiometric to Vcc: + * + * ao_accel_ref ref + * ------------ = ----- + * 32767 Vcc + * + * + * ao_accel_ref = 32767 * (ref / Vcc) + * + * Acceleration is measured ratiometric to the 5V supply, + * so what we want is: + * + * ao_cook_accel accel + * ------------- = ----- + * 32767 ref + * + * + * accel Vcc + * = ----- * --- + * Vcc ref + * + * ao_sample_accel 32767 + * = ------------ * ------------ + * 32767 ao_accel_ref + * + * Multiply through by 32767: + * + * ao_sample_accel * 32767 + * ao_cook_accel = -------------------- + * ao_accel_ref + * + * Now, the tricky part. Getting this to compile efficiently + * and keeping all of the values in-range. + * + * First off, we need to use a shift of 16 instead of * 32767 as SDCC + * does the obvious optimizations for byte-granularity shifts: + * + * ao_cook_accel = (ao_sample_accel << 16) / ao_accel_ref + * + * Next, lets check our input ranges: + * + * 0 <= ao_sample_accel <= 0x7fff (singled ended ADC conversion) + * 0x7000 <= ao_accel_ref <= 0x7fff (the 5V ref value is close to 0x7fff) + * + * Plugging in our input ranges, we get an output range of 0 - 0x12490, + * which is 17 bits. That won't work. If we take the accel ref and shift + * by a bit, we'll change its range: + * + * 0xe000 <= ao_accel_ref<<1 <= 0xfffe + * + * ao_cook_accel = (ao_sample_accel << 16) / (ao_accel_ref << 1) + * + * Now the output range is 0 - 0x9248, which nicely fits in 16 bits. It + * is, however, one bit too large for our signed computations. So, we + * take the result and shift that by a bit: + * + * ao_cook_accel = ((ao_sample_accel << 16) / (ao_accel_ref << 1)) >> 1 + * + * This finally creates an output range of 0 - 0x4924. As the ADC only + * provides 11 bits of data, we haven't actually lost any precision, + * just dropped a bit of noise off the low end. + */ +#if HAS_ACCEL_REF +#define ao_data_accel_sample(packet) \ + ((uint16_t) ((((uint32_t) (packet)->adc.accel << 16) / ((packet)->accel_ref << 1))) >> 1) +#else +#define ao_data_accel(packet) ((packet)->adc.accel) +#endif /* HAS_ACCEL_REF */ + +#endif /* else some other pressure sensor */ + +#endif /* _AO_DATA_H_ */ |