/* * Copyright © 2012 Keith Packard * * 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 #endif #if HAS_MPU6000 #include #endif #if HAS_HMC5883 #include #endif struct ao_data { uint16_t tick; #if HAS_ADC struct ao_adc adc; #endif #if HAS_MS5607 struct ao_ms5607_sample ms5607_raw; struct ao_ms5607_value ms5607_cooked; #endif #if HAS_MPU6000 struct ao_mpu6000_sample mpu6000; #endif #if HAS_HMC5883 struct ao_hmc5883_sample hmc5883; #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; #define ao_data_pres_cook(packet) ao_ms5607_convert(&packet->ms5607_raw, &packet->ms5607_cooked) #define ao_data_pres(packet) ((packet)->ms5607_cooked.pres) #define ao_data_temp(packet) ((packet)->ms5607_cooked.temp) #define pres_to_altitude(p) ao_pa_to_altitude(p) #else /* HAS_MS5607 */ typedef int16_t pres_t; typedef int16_t alt_t; #define ao_data_pres(packet) ((packet)->adc.pres) #define ao_data_temp(packet) ((packet)->adc.temp) #define pres_to_altitude(p) ao_pres_to_altitude(p) #define ao_data_pres_cook(p) #endif /* else HAS_MS5607 */ /* * 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 && !HAS_HIGHG_ACCEL typedef int16_t accel_t; /* MPU6000 is hooked up so that positive y is positive acceleration */ #ifndef ao_accel_axis #define ao_accel_axis accel_y #endif #define ao_data_accel(packet) ((packet)->mpu6000.ao_accel_axis) #define ao_data_accel_cook(packet) (-(packet)->mpu6000.ao_accel_axis) #define ao_data_set_accel(packet, accel) ((packet)->mpu6000.ao_accel_axis = (accel)) #define ao_data_accel_invert(a) (-(a)) #else /* HAS_MPU6000 && !HAS_HIGHG_ACCEL */ typedef int16_t accel_t; #define ao_data_accel(packet) ((packet)->adc.accel) #define ao_data_set_accel(packet, a) ((packet)->adc.accel = (a)) #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_cook(packet) \ ((uint16_t) ((((uint32_t) (packet)->adc.accel << 16) / ((packet)->adc.accel_ref << 1))) >> 1) #else #define ao_data_accel_cook(packet) ((packet)->adc.accel) #endif /* HAS_ACCEL_REF */ #endif /* else some other accel sensor */ #endif /* _AO_DATA_H_ */