/// -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*-
/*
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, either version 3 of the License, or
(at your option) any later version.
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, see <http://www.gnu.org/licenses/>.
*/
/*
* AP_ADC_ADS7844.cpp - ADC ADS7844 Library for Ardupilot Mega
* Code by Jordi Mu�oz and Jose Julio. DIYDrones.com
*
* Modified by John Ihlein 6 / 19 / 2010 to:
* 1)Prevent overflow of adc_counter when more than 8 samples collected between reads. Probably
* only an issue on initial read of ADC at program start.
* 2)Reorder analog read order as follows:
* p, q, r, ax, ay, az
* External ADC ADS7844 is connected via Serial port 2 (in SPI mode)
* TXD2 = MOSI = pin PH1
* RXD2 = MISO = pin PH0
* XCK2 = SCK = pin PH2
* Chip Select pin is PC4 (33) [PH6 (9)]
* We are using the 16 clocks per conversion timming to increase efficiency (fast)
*
* The sampling frequency is 1kHz (Timer2 overflow interrupt)
*
* So if our loop is at 50Hz, our needed sampling freq should be 100Hz, so
* we have an 10x oversampling and averaging.
*
* Methods:
* Init() : Initialization of interrupts an Timers (Timer2 overflow interrupt)
* Ch(ch_num) : Return the ADC channel value
*
* // HJI - Input definitions. USB connector assumed to be on the left, Rx and servo
* // connector pins to the rear. IMU shield components facing up. These are board
* // referenced sensor inputs, not device referenced.
* On Ardupilot Mega Hardware, oriented as described above:
* Chennel 0 : yaw rate, r
* Channel 1 : roll rate, p
* Channel 2 : pitch rate, q
* Channel 3 : x / y gyro temperature
* Channel 4 : x acceleration, aX
* Channel 5 : y acceleration, aY
* Channel 6 : z acceleration, aZ
* Channel 7 : Differential pressure sensor port
*
*/
#include <AP_Progmem.h>
#include <AP_Common.h>
#include <AP_HAL.h>
#include "AP_ADC_ADS7844.h"
extern const AP_HAL::HAL& hal;
// DO NOT CHANGE FROM 8!!
#define ADC_ACCEL_FILTER_SIZE 8
// Commands for reading ADC channels on ADS7844
static const unsigned char adc_cmd[17] =
{ 0x87, 0, 0xC7, 0, 0x97, 0, 0xD7, 0, 0xA7, 0, 0xE7, 0, 0xB7, 0, 0xF7};
// the sum of the values since last read
static volatile uint32_t _sum[8];
// how many values we've accumulated since last read
static volatile uint16_t _count[8];
// variables to calculate time period over which a group of samples were
// collected
// time we start collecting sample (reset on update)
static volatile uint32_t _ch6_delta_time_start_micros = 0;
// time latest sample was collected
static volatile uint32_t _ch6_last_sample_time_micros = 0;
void AP_ADC_ADS7844::read(void)
{
static int semfail_ctr = 0;
uint8_t ch;
/** Take nonblocking: ::read happens from the TimerProcess context! */
bool got = _spi_sem->take_nonblocking();
if (!got) {
semfail_ctr++;
if (semfail_ctr > 100) {
hal.scheduler->panic(PSTR("PANIC: failed to take _spi_sem "
"100 times in AP_ADC_ADS7844::read"));
}
return;
} else {
semfail_ctr = 0;
}
uint8_t rx[17];
_spi->transaction(adc_cmd, rx, 17);
for (ch = 0; ch < 8; ch++) {
uint16_t v = (rx[2*ch+1] << 8) | rx[2*ch+2];
if (v & 0x8007) {
// this is a 12-bit ADC, shifted by 3 bits.
// if we get other bits set then the value is
// bogus and should be ignored
continue;
}
if (++_count[ch] == 0) {
// overflow ... shouldn't happen too often
// unless we're just not using the
// channel. Notice that we overflow the count
// to 1 here, not zero, as otherwise the
// reader below could get a division by zero
_sum[ch] = 0;
_count[ch] = 1;
}
_sum[ch] += (v >> 3);
}
_spi_sem->give();
// record time of this sample
_ch6_last_sample_time_micros = hal.scheduler->micros();
}
// Constructors ////////////////////////////////////////////////////////////////
AP_ADC_ADS7844::AP_ADC_ADS7844() { }
// Public Methods //////////////////////////////////////////////////////////////
void AP_ADC_ADS7844::Init()
{
hal.scheduler->suspend_timer_procs();
_spi = hal.spi->device(AP_HAL::SPIDevice_ADS7844);
if (_spi == NULL) {
hal.scheduler->panic(PSTR("PANIC: AP_ADC_ADS7844 missing SPI device "
"driver\n"));
}
_spi_sem = _spi->get_semaphore();
if (_spi_sem == NULL) {
hal.scheduler->panic(PSTR("PANIC: AP_ADC_ADS7844 missing SPI device "
"semaphore"));
}
if (!_spi_sem->take(0)) {
hal.scheduler->panic(PSTR("PANIC: failed to take _spi_sem in"
"AP_ADC_ADS7844::Init"));
}
_spi->cs_assert();
// get an initial value for each channel. This ensures
// _count[] is never zero
for (uint8_t i=0; i<8; i++) {
uint16_t adc_tmp;
adc_tmp = _spi->transfer(0) << 8;
adc_tmp |= _spi->transfer(adc_cmd[i + 1]);
_count[i] = 1;
_sum[i] = adc_tmp;
}
_spi->cs_release();
_spi_sem->give();
_ch6_last_sample_time_micros = hal.scheduler->micros();
hal.scheduler->register_timer_process(AP_HAL_MEMBERPROC(&AP_ADC_ADS7844::read));
hal.scheduler->resume_timer_procs();
}
// Read one channel value
float AP_ADC_ADS7844::Ch(uint8_t ch_num)
{
uint16_t count;
uint32_t sum;
// ensure we have at least one value
while (_count[ch_num] == 0) /* noop */;
// grab the value with timer procs disabled, and clear the count
hal.scheduler->suspend_timer_procs();
count = _count[ch_num];
sum = _sum[ch_num];
_count[ch_num] = 0;
_sum[ch_num] = 0;
hal.scheduler->resume_timer_procs();
return ((float)sum)/count;
}
// see if Ch6() can return new data
bool AP_ADC_ADS7844::new_data_available(const uint8_t *channel_numbers)
{
uint8_t i;
for (i=0; i<6; i++) {
if (_count[channel_numbers[i]] == 0) {
return false;
}
}
return true;
}
// Read 6 channel values
// this assumes that the counts for all of the 6 channels are
// equal. This will only be true if we always consistently access a
// sensor by either Ch6() or Ch() and never mix them. If you mix them
// then you will get very strange results
uint32_t AP_ADC_ADS7844::Ch6(const uint8_t *channel_numbers, float *result)
{
uint16_t count[6];
uint32_t sum[6];
uint8_t i;
// ensure we have at least one value
for (i=0; i<6; i++) {
while (_count[channel_numbers[i]] == 0) /* noop */;
}
// grab the values with timer procs disabled, and clear the counts
hal.scheduler->suspend_timer_procs();
for (i=0; i<6; i++) {
count[i] = _count[channel_numbers[i]];
sum[i] = _sum[channel_numbers[i]];
_count[channel_numbers[i]] = 0;
_sum[channel_numbers[i]] = 0;
}
// calculate the delta time.
// we do this before re-enabling interrupts because another sensor read could fire immediately and change the _last_sensor_time value
uint32_t ret = _ch6_last_sample_time_micros - _ch6_delta_time_start_micros;
_ch6_delta_time_start_micros = _ch6_last_sample_time_micros;
hal.scheduler->resume_timer_procs();
// calculate averages. We keep this out of the cli region
// to prevent us stalling the ISR while doing the
// division. That costs us 36 bytes of stack, but I think its
// worth it.
for (i = 0; i < 6; i++) {
result[i] = sum[i] / (float)count[i];
}
// return number of microseconds since last call
return ret;
}
/// Get minimum number of samples read from the sensors
uint16_t AP_ADC_ADS7844::num_samples_available(const uint8_t *channel_numbers)
{
// get count of first channel as a base
uint16_t min_count = _count[channel_numbers[0]];
// reduce to minimum count of all other channels
for (uint8_t i=1; i<6; i++) {
if (_count[channel_numbers[i]] < min_count) {
min_count = _count[channel_numbers[i]];
}
}
return min_count;
}