mirror of https://github.com/ArduPilot/ardupilot
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
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AP_ADC_ADS7844.cpp - ADC ADS7844 Library for Ardupilot Mega
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Code by Jordi Mu<EFBFBD>oz and Jose Julio. DIYDrones.com
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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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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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p, q, r, ax, ay, az
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This library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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This library is free software; you can redistribute it and / or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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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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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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The sampling frequency is 400Hz (Timer2 overflow interrupt)
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So if our loop is at 50Hz, our needed sampling freq should be 100Hz, so
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@ -34,7 +34,7 @@
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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 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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@ -42,28 +42,28 @@
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*/
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extern "C" {
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// AVR LibC Includes
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#include <inttypes.h>
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#include <avr/interrupt.h>
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#include "WConstants.h"
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// AVR LibC Includes
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#include <inttypes.h>
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#include <avr/interrupt.h>
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#include "WConstants.h"
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}
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#include "AP_ADC_ADS7844.h"
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// Commands for reading ADC channels on ADS7844
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static const unsigned char adc_cmd[9]= { 0x87, 0xC7, 0x97, 0xD7, 0xA7, 0xE7, 0xB7, 0xF7, 0x00 };
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static volatile unsigned int adc_value[8] = { 0, 0, 0, 0, 0, 0, 0, 0 };
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static volatile unsigned char adc_counter[8] = { 0, 0, 0, 0, 0, 0, 0, 0 };
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static const unsigned char adc_cmd[9] = { 0x87, 0xC7, 0x97, 0xD7, 0xA7, 0xE7, 0xB7, 0xF7, 0x00 };
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static volatile uint16_t _filter[8][ADC_FILTER_SIZE];
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static volatile uint8_t _filter_index;
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static unsigned char ADC_SPI_transfer(unsigned char data)
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{
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/* Wait for empty transmit buffer */
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while ( !( UCSR2A & (1<<UDRE2)) );
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while ( !( UCSR2A & (1 << UDRE2)) );
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/* Put data into buffer, sends the data */
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UDR2 = data;
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/* Wait for data to be received */
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while ( !(UCSR2A & (1<<RXC2)) );
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while ( !(UCSR2A & (1 << RXC2)) );
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/* Get and return received data from buffer */
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return UDR2;
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}
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ISR (TIMER2_OVF_vect)
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{
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uint8_t ch;
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unsigned int adc_tmp;
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uint8_t ch;
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uint16_t adc_tmp;
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//bit_set(PORTL,6); // To test performance
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bit_clear(PORTC,4); // Enable Chip Select (PIN PC4)
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ADC_SPI_transfer(adc_cmd[0]); // Command to read the first channel
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for (ch=0;ch<8;ch++)
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{
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if (adc_counter[ch] >= 16) // To prevent overflow of adc_value
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{ //
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adc_value[ch] /= 2;
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adc_counter[ch] /= 2;
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}
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adc_tmp = ADC_SPI_transfer(0)<<8; // Read first byte
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adc_tmp |= ADC_SPI_transfer(adc_cmd[ch+1]); // Read second byte and send next command
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adc_value[ch] += adc_tmp>>3; // Shift to 12 bits
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adc_counter[ch]++; // Number of samples
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}
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bit_set(PORTC,4); // Disable Chip Select (PIN PC4)
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//bit_clear(PORTL,6); // To test performance
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TCNT2 = 104; // 400 Hz
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//bit_set(PORTL,6); // To test performance
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bit_clear(PORTC, 4); // Enable Chip Select (PIN PC4)
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ADC_SPI_transfer(adc_cmd[0]); // Command to read the first channel
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for (ch = 0; ch < 8; ch++){
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adc_tmp = ADC_SPI_transfer(0) << 8; // Read first byte
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adc_tmp |= ADC_SPI_transfer(adc_cmd[ch + 1]); // Read second byte and send next command
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// Fill our Moving average filter
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_filter[ch][_filter_index] = adc_tmp >> 3;
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}
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// increment our filter
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_filter_index++;
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// loop our filter
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if(_filter_index == ADC_FILTER_SIZE)
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_filter_index = 0;
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bit_set(PORTC, 4); // Disable Chip Select (PIN PC4)
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//bit_clear(PORTL,6); // To test performance
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TCNT2 = 104; // 400 Hz
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}
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@ -103,45 +109,50 @@ AP_ADC_ADS7844::AP_ADC_ADS7844()
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// Public Methods //////////////////////////////////////////////////////////////
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void AP_ADC_ADS7844::Init(void)
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{
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pinMode(ADC_CHIP_SELECT,OUTPUT);
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pinMode(ADC_CHIP_SELECT, OUTPUT);
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digitalWrite(ADC_CHIP_SELECT,HIGH); // Disable device (Chip select is active low)
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digitalWrite(ADC_CHIP_SELECT, HIGH); // Disable device (Chip select is active low)
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// Setup Serial Port2 in SPI mode
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UBRR2 = 0;
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DDRH |= (1<<PH2); // SPI clock XCK2 (PH2) as output. This enable SPI Master mode
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UBRR2 = 0;
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DDRH |= (1 << PH2); // SPI clock XCK2 (PH2) as output. This enable SPI Master mode
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// Set MSPI mode of operation and SPI data mode 0.
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UCSR2C = (1<<UMSEL21)|(1<<UMSEL20); //|(0<<UCPHA2)|(0<<UCPOL2);
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UCSR2C = (1 << UMSEL21) | (1 << UMSEL20); // |(0 << UCPHA2) | (0 << UCPOL2);
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// Enable receiver and transmitter.
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UCSR2B = (1<<RXEN2)|(1<<TXEN2);
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UCSR2B = (1 << RXEN2) | (1 << TXEN2);
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// Set Baud rate
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UBRR2 = 2; // SPI clock running at 2.6MHz
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UBRR2 = 2; // SPI clock running at 2.6MHz
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// Enable Timer2 Overflow interrupt to capture ADC data
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TIMSK2 = 0; // Disable interrupts
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TCCR2A = 0; // normal counting mode
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TCCR2B = _BV(CS21)|_BV(CS22); // Set prescaler of 256
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TCNT2 = 0;
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TIFR2 = _BV(TOV2); // clear pending interrupts;
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TIMSK2 = _BV(TOIE2) ; // enable the overflow interrupt
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TIMSK2 = 0; // Disable interrupts
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TCCR2A = 0; // normal counting mode
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TCCR2B = _BV(CS21) | _BV(CS22); // Set prescaler of 256
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TCNT2 = 0;
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TIFR2 = _BV(TOV2); // clear pending interrupts;
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TIMSK2 = _BV(TOIE2) ; // enable the overflow interrupt
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}
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// Read one channel value
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int AP_ADC_ADS7844::Ch(unsigned char ch_num)
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int AP_ADC_ADS7844::Ch(unsigned char ch_num)
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{
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int result;
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uint16_t result = 0;
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while(adc_counter[ch_num] < 2) { } // Wait for at least 2 samples in accumlator
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//while(adc_counter[ch_num] < 2) { } // Wait for at least 2 samples in accumlator
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cli();
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if (adc_counter[ch_num]>0)
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result = adc_value[ch_num]/adc_counter[ch_num];
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else
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result = 0;
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adc_value[ch_num] = 0; // Initialize for next reading
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adc_counter[ch_num] = 0;
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sei();
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return(result);
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// stop interrupts
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cli();
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// sum our filter
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for(uint8_t i = 0; i < ADC_FILTER_SIZE; i++){
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result += _filter[ch_num][i];
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}
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// resume interrupts
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sei();
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// average our sampels
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result /= ADC_FILTER_SIZE;
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return(result);
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}
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#define ADC_DATAIN 50 // MISO
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#define ADC_SPICLOCK 52 // SCK
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#define ADC_CHIP_SELECT 33 // PC4 9 // PH6 Puerto:0x08 Bit mask : 0x40
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#define ADC_FILTER_SIZE 6
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#include "AP_ADC.h"
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#include <inttypes.h>
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class AP_ADC_ADS7844 : public AP_ADC
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{
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public:
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public:
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AP_ADC_ADS7844(); // Constructor
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void Init();
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int Ch(unsigned char ch_num);
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private:
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void Init();
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int Ch(unsigned char ch_num);
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private:
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};
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#endif
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