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Implemented moving average filter to deal with noise issues on quads, default is a 6 member filter. 

git-svn-id: https://arducopter.googlecode.com/svn/trunk@2551 f9c3cf11-9bcb-44bc-f272-b75c42450872
mission-4.1.18
jasonshort 14 years ago
parent
595266152b
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c1ddd58d4c
2 changed files with 86 additions and 72 deletions
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  1. 139
      libraries/AP_ADC/AP_ADC_ADS7844.cpp
  2. 11
      libraries/AP_ADC/AP_ADC_ADS7844.h

139
libraries/AP_ADC/AP_ADC_ADS7844.cpp
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@ -2,22 +2,22 @@ @@ -2,22 +2,22 @@
AP_ADC_ADS7844.cpp - ADC ADS7844 Library for Ardupilot Mega
Code by Jordi Mu<EFBFBD>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.
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
p, q, r, ax, ay, az
This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
This library is free software; you can redistribute it and / or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
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)]
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 400Hz (Timer2 overflow interrupt)
So if our loop is at 50Hz, our needed sampling freq should be 100Hz, so
@ -34,7 +34,7 @@ @@ -34,7 +34,7 @@
Chennel 0 : yaw rate, r
Channel 1 : roll rate, p
Channel 2 : pitch rate, q
Channel 3 : x/y gyro temperature
Channel 3 : x / y gyro temperature
Channel 4 : x acceleration, aX
Channel 5 : y acceleration, aY
Channel 6 : z acceleration, aZ
@ -42,28 +42,28 @@ @@ -42,28 +42,28 @@
*/
extern "C" {
// AVR LibC Includes
#include <inttypes.h>
#include <avr/interrupt.h>
#include "WConstants.h"
// AVR LibC Includes
#include <inttypes.h>
#include <avr/interrupt.h>
#include "WConstants.h"
}
#include "AP_ADC_ADS7844.h"
// Commands for reading ADC channels on ADS7844
static const unsigned char adc_cmd[9]= { 0x87, 0xC7, 0x97, 0xD7, 0xA7, 0xE7, 0xB7, 0xF7, 0x00 };
static volatile unsigned int adc_value[8] = { 0, 0, 0, 0, 0, 0, 0, 0 };
static volatile unsigned char adc_counter[8] = { 0, 0, 0, 0, 0, 0, 0, 0 };
static const unsigned char adc_cmd[9] = { 0x87, 0xC7, 0x97, 0xD7, 0xA7, 0xE7, 0xB7, 0xF7, 0x00 };
static volatile uint16_t _filter[8][ADC_FILTER_SIZE];
static volatile uint8_t _filter_index;
static unsigned char ADC_SPI_transfer(unsigned char data)
{
/* Wait for empty transmit buffer */
while ( !( UCSR2A & (1<<UDRE2)) );
while ( !( UCSR2A & (1 << UDRE2)) );
/* Put data into buffer, sends the data */
UDR2 = data;
/* Wait for data to be received */
while ( !(UCSR2A & (1<<RXC2)) );
while ( !(UCSR2A & (1 << RXC2)) );
/* Get and return received data from buffer */
return UDR2;
}
@ -71,27 +71,33 @@ static unsigned char ADC_SPI_transfer(unsigned char data) @@ -71,27 +71,33 @@ static unsigned char ADC_SPI_transfer(unsigned char data)
ISR (TIMER2_OVF_vect)
{
uint8_t ch;
unsigned int adc_tmp;
//bit_set(PORTL,6); // To test performance
bit_clear(PORTC,4); // Enable Chip Select (PIN PC4)
ADC_SPI_transfer(adc_cmd[0]); // Command to read the first channel
for (ch=0;ch<8;ch++)
{
if (adc_counter[ch] >= 16) // To prevent overflow of adc_value
{ //
adc_value[ch] /= 2;
adc_counter[ch] /= 2;
}
adc_tmp = ADC_SPI_transfer(0)<<8; // Read first byte
adc_tmp |= ADC_SPI_transfer(adc_cmd[ch+1]); // Read second byte and send next command
adc_value[ch] += adc_tmp>>3; // Shift to 12 bits
adc_counter[ch]++; // Number of samples
}
bit_set(PORTC,4); // Disable Chip Select (PIN PC4)
//bit_clear(PORTL,6); // To test performance
TCNT2 = 104; // 400 Hz
uint8_t ch;
uint16_t adc_tmp;
//bit_set(PORTL,6); // To test performance
bit_clear(PORTC, 4); // Enable Chip Select (PIN PC4)
ADC_SPI_transfer(adc_cmd[0]); // Command to read the first channel
for (ch = 0; ch < 8; ch++){
adc_tmp = ADC_SPI_transfer(0) << 8; // Read first byte
adc_tmp |= ADC_SPI_transfer(adc_cmd[ch + 1]); // Read second byte and send next command
// Fill our Moving average filter
_filter[ch][_filter_index] = adc_tmp >> 3;
}
// increment our filter
_filter_index++;
// loop our filter
if(_filter_index == ADC_FILTER_SIZE)
_filter_index = 0;
bit_set(PORTC, 4); // Disable Chip Select (PIN PC4)
//bit_clear(PORTL,6); // To test performance
TCNT2 = 104; // 400 Hz
}
@ -103,45 +109,50 @@ AP_ADC_ADS7844::AP_ADC_ADS7844() @@ -103,45 +109,50 @@ AP_ADC_ADS7844::AP_ADC_ADS7844()
// Public Methods //////////////////////////////////////////////////////////////
void AP_ADC_ADS7844::Init(void)
{
pinMode(ADC_CHIP_SELECT,OUTPUT);
pinMode(ADC_CHIP_SELECT, OUTPUT);
digitalWrite(ADC_CHIP_SELECT,HIGH); // Disable device (Chip select is active low)
digitalWrite(ADC_CHIP_SELECT, HIGH); // Disable device (Chip select is active low)
// Setup Serial Port2 in SPI mode
UBRR2 = 0;
DDRH |= (1<<PH2); // SPI clock XCK2 (PH2) as output. This enable SPI Master mode
UBRR2 = 0;
DDRH |= (1 << PH2); // SPI clock XCK2 (PH2) as output. This enable SPI Master mode
// Set MSPI mode of operation and SPI data mode 0.
UCSR2C = (1<<UMSEL21)|(1<<UMSEL20); //|(0<<UCPHA2)|(0<<UCPOL2);
UCSR2C = (1 << UMSEL21) | (1 << UMSEL20); // |(0 << UCPHA2) | (0 << UCPOL2);
// Enable receiver and transmitter.
UCSR2B = (1<<RXEN2)|(1<<TXEN2);
UCSR2B = (1 << RXEN2) | (1 << TXEN2);
// Set Baud rate
UBRR2 = 2; // SPI clock running at 2.6MHz
UBRR2 = 2; // SPI clock running at 2.6MHz
// Enable Timer2 Overflow interrupt to capture ADC data
TIMSK2 = 0; // Disable interrupts
TCCR2A = 0; // normal counting mode
TCCR2B = _BV(CS21)|_BV(CS22); // Set prescaler of 256
TCNT2 = 0;
TIFR2 = _BV(TOV2); // clear pending interrupts;
TIMSK2 = _BV(TOIE2) ; // enable the overflow interrupt
TIMSK2 = 0; // Disable interrupts
TCCR2A = 0; // normal counting mode
TCCR2B = _BV(CS21) | _BV(CS22); // Set prescaler of 256
TCNT2 = 0;
TIFR2 = _BV(TOV2); // clear pending interrupts;
TIMSK2 = _BV(TOIE2) ; // enable the overflow interrupt
}
// Read one channel value
int AP_ADC_ADS7844::Ch(unsigned char ch_num)
{
int result;
uint16_t result = 0;
//while(adc_counter[ch_num] < 2) { } // Wait for at least 2 samples in accumlator
// stop interrupts
cli();
// sum our filter
for(uint8_t i = 0; i < ADC_FILTER_SIZE; i++){
result += _filter[ch_num][i];
}
while(adc_counter[ch_num] < 2) { } // Wait for at least 2 samples in accumlator
// resume interrupts
sei();
cli();
if (adc_counter[ch_num]>0)
result = adc_value[ch_num]/adc_counter[ch_num];
else
result = 0;
// average our sampels
result /= ADC_FILTER_SIZE;
adc_value[ch_num] = 0; // Initialize for next reading
adc_counter[ch_num] = 0;
sei();
return(result);
return(result);
}

11
libraries/AP_ADC/AP_ADC_ADS7844.h
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@ -9,16 +9,19 @@ @@ -9,16 +9,19 @@
#define ADC_DATAIN 50 // MISO
#define ADC_SPICLOCK 52 // SCK
#define ADC_CHIP_SELECT 33 // PC4 9 // PH6 Puerto:0x08 Bit mask : 0x40
#define ADC_FILTER_SIZE 6
#include "AP_ADC.h"
#include <inttypes.h>
class AP_ADC_ADS7844 : public AP_ADC
{
public:
public:
AP_ADC_ADS7844(); // Constructor
void Init();
int Ch(unsigned char ch_num);
private:
void Init();
int Ch(unsigned char ch_num);
private:
};
#endif

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