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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
This commit is contained in:
jasonshort 2011-06-12 23:50:15 +00:00
parent b07c32acd0
commit 65345160d1
2 changed files with 83 additions and 69 deletions
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83
libraries/AP_ADC/AP_ADC_ADS7844.cpp
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@ -2,13 +2,13 @@
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:
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
This library is free software; you can redistribute it and/or
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.
@ -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
@ -52,18 +52,18 @@ extern "C" {
// 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;
}
@ -72,24 +72,30 @@ static unsigned char ADC_SPI_transfer(unsigned char data)
ISR (TIMER2_OVF_vect)
{
uint8_t ch;
unsigned int adc_tmp;
uint16_t adc_tmp;
//bit_set(PORTL,6); // To test performance
bit_clear(PORTC,4); // Enable Chip Select (PIN PC4)
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;
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;
}
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)
// 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
}
@ -103,17 +109,17 @@ 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
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
@ -121,7 +127,7 @@ void AP_ADC_ADS7844::Init(void)
// 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
TCCR2B = _BV(CS21) | _BV(CS22); // Set prescaler of 256
TCNT2 = 0;
TIFR2 = _BV(TOV2); // clear pending interrupts;
TIMSK2 = _BV(TOIE2) ; // enable the overflow interrupt
@ -130,18 +136,23 @@ void AP_ADC_ADS7844::Init(void)
// 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
//while(adc_counter[ch_num] < 2) { } // Wait for at least 2 samples in accumlator
// stop interrupts
cli();
if (adc_counter[ch_num]>0)
result = adc_value[ch_num]/adc_counter[ch_num];
else
result = 0;
adc_value[ch_num] = 0; // Initialize for next reading
adc_counter[ch_num] = 0;
// sum our filter
for(uint8_t i = 0; i < ADC_FILTER_SIZE; i++){
result += _filter[ch_num][i];
}
// resume interrupts
sei();
// average our sampels
result /= ADC_FILTER_SIZE;
return(result);
}

3
libraries/AP_ADC/AP_ADC_ADS7844.h
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@ -9,8 +9,10 @@
#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
{
@ -18,6 +20,7 @@ class AP_ADC_ADS7844 : public AP_ADC
AP_ADC_ADS7844(); // Constructor
void Init();
int Ch(unsigned char ch_num);
private:
};