mirror of https://github.com/ArduPilot/ardupilot
271 lines
8.6 KiB
C++
271 lines
8.6 KiB
C++
/// -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*-
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/*
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This program is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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/*
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* AP_ADC_ADS7844.cpp - ADC ADS7844 Library for Ardupilot Mega
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* Code by Jordi Mu<4D>oz and Jose Julio. DIYDrones.com
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*
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* Modified by John Ihlein 6 / 19 / 2010 to:
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* 1)Prevent overflow of adc_counter when more than 8 samples collected between reads. Probably
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* only an issue on initial read of ADC at program start.
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* 2)Reorder analog read order as follows:
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* p, q, r, ax, ay, az
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* External ADC ADS7844 is connected via Serial port 2 (in SPI mode)
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* TXD2 = MOSI = pin PH1
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* RXD2 = MISO = pin PH0
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* XCK2 = SCK = pin PH2
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* Chip Select pin is PC4 (33) [PH6 (9)]
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* We are using the 16 clocks per conversion timming to increase efficiency (fast)
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*
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* The sampling frequency is 1kHz (Timer2 overflow interrupt)
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*
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* So if our loop is at 50Hz, our needed sampling freq should be 100Hz, so
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* we have an 10x oversampling and averaging.
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*
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* Methods:
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* Init() : Initialization of interrupts an Timers (Timer2 overflow interrupt)
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* Ch(ch_num) : Return the ADC channel value
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*
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* // HJI - Input definitions. USB connector assumed to be on the left, Rx and servo
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* // connector pins to the rear. IMU shield components facing up. These are board
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* // referenced sensor inputs, not device referenced.
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* On Ardupilot Mega Hardware, oriented as described above:
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* Chennel 0 : yaw rate, r
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* Channel 1 : roll rate, p
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* Channel 2 : pitch rate, q
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* Channel 3 : x / y gyro temperature
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* Channel 4 : x acceleration, aX
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* Channel 5 : y acceleration, aY
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* Channel 6 : z acceleration, aZ
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* Channel 7 : Differential pressure sensor port
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*
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*/
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#include <AP_Progmem.h>
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#include <AP_Common.h>
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#include <AP_HAL.h>
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#include "AP_ADC_ADS7844.h"
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extern const AP_HAL::HAL& hal;
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// DO NOT CHANGE FROM 8!!
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#define ADC_ACCEL_FILTER_SIZE 8
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// Commands for reading ADC channels on ADS7844
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static const unsigned char adc_cmd[17] =
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{ 0x87, 0, 0xC7, 0, 0x97, 0, 0xD7, 0, 0xA7, 0, 0xE7, 0, 0xB7, 0, 0xF7};
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// the sum of the values since last read
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static volatile uint32_t _sum[8];
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// how many values we've accumulated since last read
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static volatile uint16_t _count[8];
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// variables to calculate time period over which a group of samples were
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// collected
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// time we start collecting sample (reset on update)
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static volatile uint32_t _ch6_delta_time_start_micros = 0;
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// time latest sample was collected
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static volatile uint32_t _ch6_last_sample_time_micros = 0;
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void AP_ADC_ADS7844::read(void)
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{
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static int semfail_ctr = 0;
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uint8_t ch;
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/** Take nonblocking: ::read happens from the TimerProcess context! */
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bool got = _spi_sem->take_nonblocking();
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if (!got) {
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semfail_ctr++;
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if (semfail_ctr > 100) {
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hal.scheduler->panic(PSTR("PANIC: failed to take _spi_sem "
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"100 times in AP_ADC_ADS7844::read"));
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}
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return;
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} else {
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semfail_ctr = 0;
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}
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uint8_t rx[17];
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_spi->transaction(adc_cmd, rx, 17);
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for (ch = 0; ch < 8; ch++) {
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uint16_t v = (rx[2*ch+1] << 8) | rx[2*ch+2];
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if (v & 0x8007) {
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// this is a 12-bit ADC, shifted by 3 bits.
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// if we get other bits set then the value is
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// bogus and should be ignored
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continue;
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}
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if (++_count[ch] == 0) {
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// overflow ... shouldn't happen too often
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// unless we're just not using the
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// channel. Notice that we overflow the count
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// to 1 here, not zero, as otherwise the
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// reader below could get a division by zero
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_sum[ch] = 0;
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_count[ch] = 1;
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}
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_sum[ch] += (v >> 3);
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}
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_spi_sem->give();
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// record time of this sample
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_ch6_last_sample_time_micros = hal.scheduler->micros();
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}
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// Constructors ////////////////////////////////////////////////////////////////
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AP_ADC_ADS7844::AP_ADC_ADS7844() { }
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// Public Methods //////////////////////////////////////////////////////////////
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void AP_ADC_ADS7844::Init()
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{
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hal.scheduler->suspend_timer_procs();
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_spi = hal.spi->device(AP_HAL::SPIDevice_ADS7844);
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if (_spi == NULL) {
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hal.scheduler->panic(PSTR("PANIC: AP_ADC_ADS7844 missing SPI device "
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"driver\n"));
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}
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_spi_sem = _spi->get_semaphore();
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if (_spi_sem == NULL) {
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hal.scheduler->panic(PSTR("PANIC: AP_ADC_ADS7844 missing SPI device "
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"semaphore"));
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}
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if (!_spi_sem->take(0)) {
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hal.scheduler->panic(PSTR("PANIC: failed to take _spi_sem in"
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"AP_ADC_ADS7844::Init"));
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}
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_spi->cs_assert();
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// get an initial value for each channel. This ensures
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// _count[] is never zero
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for (uint8_t i=0; i<8; i++) {
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uint16_t adc_tmp;
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adc_tmp = _spi->transfer(0) << 8;
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adc_tmp |= _spi->transfer(adc_cmd[i + 1]);
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_count[i] = 1;
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_sum[i] = adc_tmp;
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}
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_spi->cs_release();
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_spi_sem->give();
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_ch6_last_sample_time_micros = hal.scheduler->micros();
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hal.scheduler->register_timer_process(AP_HAL_MEMBERPROC(&AP_ADC_ADS7844::read));
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hal.scheduler->resume_timer_procs();
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}
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// Read one channel value
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float AP_ADC_ADS7844::Ch(uint8_t ch_num)
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{
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uint16_t count;
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uint32_t sum;
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// ensure we have at least one value
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while (_count[ch_num] == 0) /* noop */;
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// grab the value with timer procs disabled, and clear the count
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hal.scheduler->suspend_timer_procs();
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count = _count[ch_num];
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sum = _sum[ch_num];
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_count[ch_num] = 0;
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_sum[ch_num] = 0;
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hal.scheduler->resume_timer_procs();
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return ((float)sum)/count;
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}
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// see if Ch6() can return new data
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bool AP_ADC_ADS7844::new_data_available(const uint8_t *channel_numbers)
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{
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uint8_t i;
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for (i=0; i<6; i++) {
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if (_count[channel_numbers[i]] == 0) {
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return false;
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}
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}
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return true;
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}
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// Read 6 channel values
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// this assumes that the counts for all of the 6 channels are
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// equal. This will only be true if we always consistently access a
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// sensor by either Ch6() or Ch() and never mix them. If you mix them
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// then you will get very strange results
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uint32_t AP_ADC_ADS7844::Ch6(const uint8_t *channel_numbers, float *result)
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{
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uint16_t count[6];
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uint32_t sum[6];
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uint8_t i;
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// ensure we have at least one value
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for (i=0; i<6; i++) {
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while (_count[channel_numbers[i]] == 0) /* noop */;
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}
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// grab the values with timer procs disabled, and clear the counts
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hal.scheduler->suspend_timer_procs();
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for (i=0; i<6; i++) {
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count[i] = _count[channel_numbers[i]];
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sum[i] = _sum[channel_numbers[i]];
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_count[channel_numbers[i]] = 0;
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_sum[channel_numbers[i]] = 0;
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}
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// calculate the delta time.
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// we do this before re-enabling interrupts because another sensor read could fire immediately and change the _last_sensor_time value
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uint32_t ret = _ch6_last_sample_time_micros - _ch6_delta_time_start_micros;
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_ch6_delta_time_start_micros = _ch6_last_sample_time_micros;
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hal.scheduler->resume_timer_procs();
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// calculate averages. We keep this out of the cli region
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// to prevent us stalling the ISR while doing the
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// division. That costs us 36 bytes of stack, but I think its
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// worth it.
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for (i = 0; i < 6; i++) {
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result[i] = sum[i] / (float)count[i];
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}
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// return number of microseconds since last call
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return ret;
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}
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/// Get minimum number of samples read from the sensors
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uint16_t AP_ADC_ADS7844::num_samples_available(const uint8_t *channel_numbers)
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{
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// get count of first channel as a base
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uint16_t min_count = _count[channel_numbers[0]];
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// reduce to minimum count of all other channels
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for (uint8_t i=1; i<6; i++) {
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if (_count[channel_numbers[i]] < min_count) {
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min_count = _count[channel_numbers[i]];
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}
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}
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return min_count;
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}
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