ATtiny402 ADC value comming not properly - c

In ATtiny402 There is no increment ADC value when its came on +2.5v. Its stuck on that max adc value of when it reaches the corresponding +2.5v....there is no change even i adjust the trimpot above 2.5v. And here is code.
#include <avr/io.h> #include <util/delay.h> uint16_t volatile adcVal;
void ADC0_init(void); uint16_t ADC0_read(void);
void ADC0_init(void) { /* Disable digital input buffer */ PORTA.PIN6CTRL &= ~PORT_ISC_gm; PORTA.PIN6CTRL |= PORT_ISC_INPUT_DISABLE_gc;
/* Disable pull-up resistor */
PORTA.PIN6CTRL &= ~PORT_PULLUPEN_bm;
ADC0.CTRLB = VREF_ADC0REFEN_bm ;
VREF.CTRLA = VREF_ADC0REFSEL_1_bm;
ADC0.CTRLC |= ADC_PRESC_DIV4_gc /* CLK_PER divided by 4 */
| ADC_REFSEL_INTREF_gc; /* Internal reference */
ADC0.CTRLA |= ADC_ENABLE_bm /* ADC Enable: enabled */
| ADC_RESSEL_10BIT_gc; /* 10-bit mode */
/* Select ADC channel */
ADC0.MUXPOS = ADC_MUXPOS_AIN6_gc;
}
uint16_t ADC0_read(void) { /* Start ADC conversion */ ADC0.COMMAND = ADC_STCONV_bm;
/* Wait until ADC conversion done */
while ( !(ADC0.INTFLAGS & ADC_RESRDY_bm) )
{
;
}
/* Clear the interrupt flag by writing 1: */
ADC0.INTFLAGS = ADC_RESRDY_bm;
return ADC0.RES;
}

This writes a mask with bit ADC0REFSEL_1 set and enables 2.5V reference voltage.
VREF.CTRLA = VREF_ADC0REFSEL_1_bm;
ADC can't measure voltages above the reference.
Try different value or enable VDD as a reference on ADC0.CTRLC

Regarding the second question in the comment.
I got a decimal value 4092 without this (ADC0.RES >> 2) … and why is that working in only after 2 bit shifting
The answer is to long to put it into a comment.
You have a mistake here using ADC0.CTRLB instead of VREF.CTRLB
ADC0.CTRLB = VREF_ADC0REFEN_bm;
So VREF_ADC0REFEN_bm which equal 2 is written into SAMPNUM ADC control field and ACC4 mode is enabled. This means at every ADC conversion request it makes four conversions by itself and places the sum into ADC result register. So you should divide the result by 4 to have what you expected.
VREF works anyway because (absent) line
VREF.CTRLB = VREF_ADC0REFEN_bm;
just sets permanent enabling of ADC0REF output. Without this code line the output is enabled automatically by ADC request which requires more setup time though.

Related

i have solved my issues....yet still there some doubts..clarify me

uint16_t adc_value=0;
void ADC0_init(void)
{
/* Disable digital input buffer */
PORTA.PIN6CTRL &= ~PORT_ISC_gm;
PORTA.PIN6CTRL |= PORT_ISC_INPUT_DISABLE_gc;
/* Disable pull-up resistor */
PORTA.PIN6CTRL &= ~PORT_PULLUPEN_bm;
ADC0.CTRLB = VREF_ADC0REFEN_bm ;
VREF.CTRLA = VREF_ADC0REFSEL_4V34_gc;
ADC0.CTRLC |= ADC_PRESC_DIV4_gc /* CLK_PER divided by 4 */
| ADC_REFSEL_INTREF_gc; /* Internal reference */
ADC0.CTRLA |= ADC_ENABLE_bm /* ADC Enable: enabled */
| ADC_RESSEL_10BIT_gc; /* 10-bit mode */
/* Select ADC channel */
ADC0.MUXPOS = ADC_MUXPOS_AIN6_gc;
}
uint16_t ADC0_read(void)
{
/* Start ADC conversion */
ADC0.COMMAND = ADC_STCONV_bm;
/* Wait until ADC conversion done */
while ( !(ADC0.INTFLAGS & ADC_RESRDY_bm) )
{
;
}
/* Clear the interrupt flag by writing 1: */
ADC0.INTFLAGS = ADC_RESRDY_bm;
return (ADC0.RES >> 2);
}
i got a decimal value 4092 without this (ADC0.RES >> 2)...after i did this 2 bit right shift i got 1024...i dont understand what exactly going on...is right shift essential for getting 1024.....and why is that working in only after 2 bit shifting...please explain me....
Why are you are setting ADC0.CTRLB = VREF_ADC0REFEN_bm? VREF_ADC0REFEN_bm is intended for the VREF.CTRLB register, not the ADC0.CTRLB register.
VREF_ADC0REFEN_bm is defined as 0x02 and when you set ADC0.CTRLB to 0x02 you are setting the Sample Accumulation Number to 0x2, which means 4 samples are accumulated in the ADC Result register. That is why you have to divide by 4 to get your result back into the range of a single sample.

IIR Lowpass filter using STM32F429 Discovery board in Keil uVision

I am designing an IIR 2nd order Lowpass filter with sampling frequency = 100Hz and cutoff frequency = 10 Hz. The filter coefficients are of Chebyshev Type I using fdatool in Matlab.
But the code is not able to filter the signal (i.e. for all frequencies it gives the output with same amplitudes as the input signal) . Only minor decrease in amplitude is observed for an input signal of 10 KHz and above. I assure you that the ADC and DAC are working fine as i have tested the for FFT filter.
Here is the code:
/* Include core modules */
#include "stm32f4xx.h"
#include "stdint.h"
#include "stdlib.h"
#include "arm_math.h"
#include "my_files.h"
#define URS 2
#define numStages 1
#define NUM_TAPS 5*numStages
#define samples 3
////////ADC FUNCTION//////////////////
void ADC_configure(void)
{
RCC->APB2ENR|=1Ul<<8; // ADC1 clock enabled
ADC1->CR2|=0x00000001; // enable ADC
ADC1->CR1|=0; // single conversion ADC1 pin 0 has been selected
}
int32_t readADC(void)
{
ADC1->CR2|=(1UL<<30);
return(ADC1->DR);
}
////////DAC FUNCTION/////////////////
int32_t dv1,dv2,ds;
//---function declaration--//
// initilising DAC---------//
void DAC_init(void)
{
RCC->APB1ENR|=1UL<<29;
DAC->CR|=((1UL<<16)|(1UL<<0));
RCC->AHB1ENR|=0x00000001; // clock to gpio A
GPIOA->MODER|=0x00000F03; // pt0,4,5 in Analog mode
}
// Sending to DAC...........//
void Send_DAC(int32_t data_in1, int32_t data_in2)
{ dv1=data_in1;
dv2=data_in2<<16;
ds=dv2+dv1;
DAC->DHR12RD=ds;
}
/* IIR settings */
float32_t pState[2*numStages];
const float pCoeffs[NUM_TAPS] = {1,2,1,-1.1997,0.5157};//{b0,b1,b2,a1,a2}
/* Global variables */
float32_t Input[samples]; /* Data to be read from ADC */
float32_t InputData[samples]; /* Data to be processed */
float32_t Output[samples]; /* Output filtered Data */
arm_biquad_cascade_df2T_instance_f32 S; /* ARM IIR module */
uint16_t i;
void TIM3_Init (void) {
RCC->APB1ENR |= RCC_APB1ENR_TIM3EN; /* enable clock for TIM1 */
TIM3->PSC = 8600; /* set prescaler = 10KHz */
TIM3->ARR = 100; /* set auto-reload = 10ms */
TIM3->RCR = 0; /* set repetition counter */
TIM3->CR1 |= (1UL << URS);
TIM3->DIER = TIM_DIER_UIE; /* Update Interrupt enable */
NVIC_EnableIRQ(TIM3_IRQn); /* TIM1 Interrupt enable */
NVIC_SetPriority (TIM3_IRQn, 0);
TIM3->CR1 |= TIM_CR1_CEN; /* timer enable */
}
void TIM3_IRQHandler() {
/*Shift Operation*/
for(i=samples-1;i>0;i--){
Input[i]= Input[i-1];
InputData[i]= Input[i];
}
/* Input part from the ADC */
Input[0] = (float32_t)readADC();
InputData[0] = Input[0];
//////////IIR//////////////////////
/* Initialize the IIR module */
arm_biquad_cascade_df2T_init_f32(&S, numStages, pCoeffs, pState);
/* Process the data through the IIR module */
arm_biquad_cascade_df2T_f32(&S, InputData, Output, samples);
////////DAC Output/////////////////
Send_DAC(Input[0], Output[0]);
}
/////////main function///////////////
int main(void) {
/* Initialize system */
SystemInit();
DAC_init();
ADC_configure();
TIM3_Init();
while (1) {
}
}
Any suggestion or solution would be of great help.
Some possible problems:
Did you enable the FPU?
Check alignment for ADC (and DAC?).
Ensure the interrupt-handler does not run too long (overflow).
Good you do not use the stdlib for much more tha init, btw. But you really should use symbolic constants for the register initialization! This does not cost extra.
Not directly related, but will(!) give wrong results: If I get it right, you trigger each conversion in readADC. This leads to jitter (resulting in noise on the digitized signal); trigger the conversations by a timer (that's what the trigger system is for actually) and use the ADC-interrupt to read the data or use a DMA (the STM DMA provides a double-buffer mode which is perfect for this). In this simple example, if using DMA, you can even get along completely without interrupt and do the calculations in the main program.
For the DAC you should the same.
Not sure why use a timer anyway; the ADC can self-trigger. Is that not sufficient?
You do not need to init IIR filter every time. Do it only once in init code. Init procedure clears previous values in pState, but they are required for IIR to perform correctly. That's the reason why your filter doesn't work. Presence of FPU only influences the speed of computation.

ADC not working with ATMEGA8

I'm trying to execute the following piece of code on ATMEGA8 but the ADC doesn't seem to be working.
#include <avr/io.h>
#include "LCD.h"
int main()
{
int val=0;
ADCSRA=0x87;//ADc enabled and prescaler set to fosc/128
ADMUX= 0xC0;//REFS0 and REFS1 set using internal 2.5 volts as Vref
DDRC=0x00;// as input for the adc
PORTC=0x00;
DDRB=0xff;
while (1)
{
ADCSRA |=(1<<ADSC);
while(!(ADCSRA&(1<<ADIF)));
lcd_string("Done Conversion");
val=ADCL;
PORTB=ADCL;
ADCSRA |=(1<<ADIF);//(reseting ADIF to 1)
lcd_print(2,1,val,3);
}
return 0;
}
You have not read ADCH. The data sheet says
When ADCL is read, the ADC Data Register is not updated until ADCH is
read. Consequently, if the result is left adjusted and no more than
8-bit precision is required, it is sufficient to read ADCH. Otherwise,
ADCL must be read first, then ADCH.
val = ADCL;
val = ((ADCH<<8) | val) & 0x3F;
You are writing the result to an 8-bit port. If you want an 8-bit conversion then set the ADLAR bit in ADMUX. The 10-bit conversion will then be left-shifted by 6 bits and you can ignore the ls 2 bits in ADCL.
ADMUX = 0xE0;
...
val = ADCH;
BTW read-modify-write of ADCSRA is not recomended. To clear bit 4 – ADIF, the ADC Interrupt Flag, you could try
ADCSRA = 0x97; // rewrite config and clear ADIF
Which is your original configuration with the ADIF bit set to clear that flag. Alternatively, you could test bit 6 ADSC which remains high until the conversion is complete, and no action is required to clear it. Since you have not enabled the ADC interrupt, there is no need to clear the ADIF flag.
while (ADCSRA & (1<<ADSC)); // wait for conversion to complete

AVR ATmega keeps resetting while using printf before main loop

I'm developing a C application using avr-libc on an AVR ATmega328P microcontroller. Since I don't have an ICE debugger for it, I followed these instructions and this tutorial for making the stdio.h functions such as printf able to use the hardware UART as stdout.
That works, and I can see the output on a PC terminal connected to my target board, but the strange thing is: When I have only one printf on main, but before the main loop something is causing the processor to reset, while if I have a printf only inside the main loop or before the main loop AND inside the loop it works fine. Something like this:
#include <stdio.h>
/* stream definitions for UART input/output */
FILE uart_output = FDEV_SETUP_STREAM(uart_drv_send_byte, NULL, _FDEV_SETUP_WRITE);
FILE uart_input = FDEV_SETUP_STREAM(NULL, uart_drv_read_byte, _FDEV_SETUP_READ);
int main() {
/* Definition of stdout and stdin */
stdout = &uart_output;
stdin = &uart_input;
/* Configures Timer1 for generating a compare interrupt each 1ms (1kHz) */
timer_init()
/* UART initialization */
uart_drv_start(UBRRH_VALUE, UBRRL_VALUE, USE_2X, &PORTB, 2);
/* Sets the sleep mode to idle */
set_sleep_mode(SLEEP_MODE_IDLE);
printf("START ");
/* main loop */
while(1) {
printf("LOOP ");
/* Sleeps so the main loop iterates only on interrupts (avoids busy loop) */
sleep_mode();
}
}
The code above produces the following output:
START LOOP LOOP LOOP LOOP LOOP LOOP ... LOOP
which is expected. If we comment the printf("START ") line it produces this:
LOOP LOOP LOOP LOOP LOOP LOOP LOOP ... LOOP
which is also fine. The problem is, if I don't have any printf inside the while loop, it goes like this:
START START START START START START ... START
That clearly shows the processor is being restarted, since the expected output would be just one START and nothing else while the infinite loop goes on being awaken only on the 1 kHz timer interrupts. Why is this happening? I should stress there's no watchdog timer configured (if there was, the cases where only LOOP is printed would be interrupted by a new START also).
Monitoring execution using GPIO pins
To try to get some insight into the situation, I turned GPIO pins ON and OFF around the problematic print("START ") and sleep_mode in the main loop:
int main() {
/* Irrelevant parts suppressed... */
GPIO1_ON;
printf("START ");
GPIO1_OFF;
/* Main loop */
while(1) {
/* Sleeps so the main loop iterates only on interrupts (avoids busy loop) */
GPIO2_ON;
sleep_mode();
GPIO2_OFF;
}
}
It turned out that GPIO1 stays ON for 132 µs (printf("START ") call time) and then OFF for 6.6 ms - roughly the time to transmit the six characters at 9600 bit/s - and GPIO2 toggles 12 times (six times two interrupts: the UART-ready-to-transmit interrupt and the UART-empty-data-register interrupt), showing sleep active for another 1.4 ms before GPIO1 goes ON again indicating a new printf("START ") - hence after reset. I'll probably have to check out the UART code, but I'm pretty sure the non-interrupt UART version also shows the same problem, and that doesn't explain either why having a printf inside the main loop works OK, without a reset happening (I would expect the reset would happen in any case should the UART code be faulty).
(SOLVED!): For completeness, The UART init and TX code is below**
This was my first attempt in writing an interrupt driven UART driver for the AVR, but one that could be used either on a RS-232 or a RS-485, which requires activating a TX_ENABLE pin while transmitting data. It turned out that, since I had to make the code useable either on ATmega328P or ATmega644, the interrupt vectors have different names, so I used a #define TX_VECTOR to assume the right name according to the processor used. In the process of making and testing the driver the choosing of "TX_VECTOR" for the UDRE data empty interrupt ended up masking the fact I hadn't defined the USART0_TX_vect yet (this was work in progress, I might not even need both anyway...)
Right now I just defined an empty interrupt service routine (ISR) for USART0_TX_vect and the thing doesn't reset anymore, showing #PeterGibson nailed it right on. Thanks a lot!
// Interrupt vectors for Atmega328P
#if defined(__AVR_ATmega328P__)
#define RX_VECTOR USART_RX_vect
#define TX_VECTOR USART_UDRE_vect
// Interrupt vectors for Atmega644
#elif defined(__AVR_ATmega644P__)
#define RX_VECTOR USART0_RX_vect
#define TX_VECTOR USART0_UDRE_vect
#endif
ISR(TX_VECTOR)
{
uint8_t byte;
if (!ringbuffer_read_byte(&txrb, &byte)) {
/* If RS-485 is enabled, sets TX_ENABLE high */
if (TX_ENABLE_PORT)
*TX_ENABLE_PORT |= _BV(TX_ENABLE_PIN);
UDR0 = byte;
}
else {
/* No more chars to be read from ringbuffer, disables empty
* data register interrupt */
UCSR0B &= ~_BV(UDRIE0);
}
/* If RS-485 mode is on and the interrupt was called with TXC0 set it
* means transmission is over. TX_ENABLED should be cleared. */
if ((TX_ENABLE_PORT) && (UCSR0A & _BV(TXC0) & _BV(UDR0))) {
*TX_ENABLE_PORT &= ~_BV(TX_ENABLE_PIN);
UCSR0B &= ~_BV(UDRIE0);
}
}
void uart_drv_start(uint8_t ubrrh, uint8_t ubrrl, uint8_t use2x,
volatile uint8_t* rs485_tx_enable_io_port,
uint8_t rs485_tx_enable_io_pin)
{
/* Initializes TX and RX ring buffers */
ringbuffer_init(&txrb, &tx_buffer[0], UART_TX_BUFSIZE);
ringbuffer_init(&rxrb, &rx_buffer[0], UART_RX_BUFSIZE);
/* Disables UART */
UCSR0B = 0x00;
/* Initializes baud rate */
UBRR0H = ubrrh;
UBRR0L = ubrrl;
if (use2x)
UCSR0A |= _BV(U2X0);
else
UCSR0A &= ~_BV(U2X0);
/* Configures async 8N1 operation */
UCSR0C = _BV(UCSZ00) | _BV(UCSZ01);
/* If a port was specified for a pin to be used as a RS-485 driver TX_ENABLE,
* configures the pin as output and enables the TX data register empty
* interrupt so it gets disabled in the end of transmission */
if (rs485_tx_enable_io_port) {
TX_ENABLE_PORT = rs485_tx_enable_io_port;
TX_ENABLE_PIN = rs485_tx_enable_io_pin;
/* Configures the RS-485 driver as an output (on the datasheet the data
* direction register is always on the byte preceding the I/O port addr) */
*(TX_ENABLE_PORT-1) |= _BV(TX_ENABLE_PIN);
/* Clears TX_ENABLE pin (active high) */
*TX_ENABLE_PORT &= ~_BV(TX_ENABLE_PIN);
/* Enables end of transmission interrupt */
UCSR0B = _BV(TXCIE0);
}
/* Enables receptor, transmitter and RX complete interrupts */
UCSR0B |= _BV(RXEN0) | _BV(TXEN0) | _BV(RXCIE0);
}
FIXED UART CODE (NOW WORKING 100%!)
In order to help anyone interested or developing a similar interrupt driven UART driver for the AVR ATmega, here it goes the code with the problems above fixed and tested. Thanks to everyone who helped me spot the problem with the missing ISR!
// Interrupt vectors for Atmega328P
#if defined(__AVR_ATmega328P__)
#define RX_BYTE_AVAILABLE USART_RX_vect
#define TX_FRAME_ENDED USART_TX_vect
#define TX_DATA_REGISTER_EMPTY USART_UDRE_vect
// Interrupt vectors for Atmega644
#elif defined(__AVR_ATmega644P__)
#define RX_BYTE_AVAILABLE USART0_RX_vect
#define TX_FRAME_ENDED USART0_TX_vect
#define TX_DATA_REGISTER_EMPTY USART0_UDRE_vect
#endif
/* I/O port containing the pin to be used as TX_ENABLE for the RS-485 driver */
static volatile uint8_t* TX_ENABLE_PORT = NULL;
/** Pin from the I/O port to be used as TX_ENABLE for the RS-485 driver */
static volatile uint8_t TX_ENABLE_PIN = 0;
ISR(RX_BYTE_AVAILABLE)
{
// Read the status and RX registers.
uint8_t status = UCSR0A;
// Framing error - treat as EOF.
if (status & _BV(FE0)) {
/* TODO: increment statistics */
}
// Overrun or parity error.
if (status & (_BV(DOR0) | _BV(UPE0))) {
/* TODO: increment statistics */
}
ringbuffer_write_byte(&rxrb, UDR0);
}
ISR(TX_FRAME_ENDED)
{
/* The end of frame interrupt will be enabled only when in RS-485 mode, so
* there is no need to test, just turn off the TX_ENABLE pin */
*TX_ENABLE_PORT &= ~_BV(TX_ENABLE_PIN);
}
ISR(TX_DATA_REGISTER_EMPTY)
{
uint8_t byte;
if (!ringbuffer_read_byte(&txrb, &byte)) {
/* If RS-485 is enabled, sets TX_ENABLE high */
if (TX_ENABLE_PORT)
*TX_ENABLE_PORT |= _BV(TX_ENABLE_PIN);
UDR0 = byte;
}
else {
/* No more chars to be read from ringbuffer, disables empty
* data register interrupt */
UCSR0B &= ~_BV(UDRIE0);
}
}
void uart_drv_start(uint8_t ubrrh, uint8_t ubrrl, uint8_t use2x,
volatile uint8_t* rs485_tx_enable_io_port,
uint8_t rs485_tx_enable_io_pin)
{
/* Initializes TX and RX ring buffers */
ringbuffer_init(&txrb, &tx_buffer[0], UART_TX_BUFSIZE);
ringbuffer_init(&rxrb, &rx_buffer[0], UART_RX_BUFSIZE);
cli();
/* Disables UART */
UCSR0B = 0x00;
/* Initializes baud rate */
UBRR0H = ubrrh;
UBRR0L = ubrrl;
if (use2x)
UCSR0A |= _BV(U2X0);
else
UCSR0A &= ~_BV(U2X0);
/* Configures async 8N1 operation */
UCSR0C = _BV(UCSZ00) | _BV(UCSZ01);
/* If a port was specified for a pin to be used as a RS-485 driver TX_ENABLE,
* configures the pin as output and enables the TX data register empty
* interrupt so it gets disabled in the end of transmission */
if (rs485_tx_enable_io_port) {
TX_ENABLE_PORT = rs485_tx_enable_io_port;
TX_ENABLE_PIN = rs485_tx_enable_io_pin;
/* Configures the RS-485 driver as an output (on the datasheet the data
* direction register is always on the byte preceding the I/O port addr) */
*(TX_ENABLE_PORT-1) |= _BV(TX_ENABLE_PIN);
/* Clears TX_ENABLE pin (active high) */
*TX_ENABLE_PORT &= ~_BV(TX_ENABLE_PIN);
/* Enables end of transmission interrupt */
UCSR0B = _BV(TXCIE0);
}
/* Enables receptor, transmitter and RX complete interrupts */
UCSR0B |= _BV(RXEN0) | _BV(TXEN0) | _BV(RXCIE0);
sei();
}
void uart_drv_send_byte(uint8_t byte, FILE *stream)
{
if (byte == '\n') {
uart_drv_send_byte('\r', stream);
}
uint8_t sreg = SREG;
cli();
/* Write byte to the ring buffer, blocking while it is full */
while(ringbuffer_write_byte(&txrb, byte)) {
/* Enable interrupts to allow emptying a full buffer */
SREG = sreg;
_NOP();
sreg = SREG;
cli();
}
/* Enables empty data register interrupt */
UCSR0B |= _BV(UDRIE0);
SREG = sreg;
}
uint8_t uart_drv_read_byte(FILE *stream)
{
uint8_t byte;
uint8_t sreg = SREG;
cli();
ringbuffer_read_byte(&rxrb, &byte);
SREG = sreg;
return byte;
}
You've possibly enabled the UDRE (Uart Data Register Empty) interrupt and not set a vector for it, so when the interrupt triggers the processor resets (according to the defaults). When printf is called continuously in the main loop, this interrupt is never triggered.
From the docs
Catch-all interrupt vector
If an unexpected interrupt occurs (interrupt is enabled and no handler
is installed, which usually indicates a bug), then the default action
is to reset the device by jumping to the reset vector. You can
override this by supplying a function named BADISR_vect which should
be defined with ISR() as such. (The name BADISR_vect is actually an
alias for __vector_default. The latter must be used inside assembly
code in case is not included.)
I ran in the same situation right now, but since I don't have a high reputation on stackoverflow, I can not vote.
here is a snippet of my initialization procedure that caused this problem to me:
void USART_Init()
{
cli();
/* Set baud rate */
UBRR0H = (uint8_t)(BAUD_PRESCALE>>8);
UBRR0L = (uint8_t)BAUD_PRESCALE;
/* Enable receiver and transmitter */
UCSR0B |= (1<<RXEN0)|(1<<TXEN0);
/* Set frame format: 8data, 1stop bit 8N1 => 86uS for a byte*/
UCSR0C |= (1<<UCSZ01)|(1<<UCSZ00);
/*enable Rx and Tx Interrupts*/
UCSR0B |= (1 << RXCIE0) | (1 << TXCIE0); //<- this was the problem
/*initialize the RingBuffer*/
RingBuffer_Init(&RxBuffer);
sei();
}
The problem was that I initially used interrupt based transmission, but later on I have changed the design and went for 10ms polling for Tx sequence, and forgotten to change this line as well in the init procedure.
Thanks very much for pointing this out Peter Gibson.

Problems with PIC A/D conversion

I am trying to read analogic signal for a sort of mouse with a pic18f14k50 controller. Here the simple circuit: http://dl.dropbox.com/u/14663091/schematiconew.pdf . I have to read analogic signal from AN9 circuit port. Main function reads from the port, and blinks 30 time if threshold is reached:
void main(void) {
InitializeSystem();
#if defined(USB_INTERRUPT)
USBDeviceAttach();
#endif
while(1) {
if((USBDeviceState < CONFIGURED_STATE)||(USBSuspendControl==1)) continue;
if(!HIDTxHandleBusy(lastTransmission))
{
int readed = myReadADC2(); //Here i tried both myReadADC2() or myReadADC1()
if(readed>40) { //If read threshold > 40, blink led 30 times
int i;
for(i=0; i<30; i++) {
Delay1KTCYx(0);
mLED_1_On();
Delay1KTCYx(0);
mLED_1_Off();
}
}
lastTransmission = HIDTxPacket(HID_EP, (BYTE*)hid_report_in, 0x03);
}//end while
}//end main
I used two method to read from the AN9 port, myReadADC() that uses OpenADC() API method:
int myReadADC(void) {
#define ADC_REF_VDD_VDD_X 0b11110011
OpenADC(ADC_FOSC_RC & ADC_RIGHT_JUST & ADC_12_TAD, ADC_CH9 & ADC_INT_OFF, ADC_REF_VDD_VDD_X & ADC_REF_VDD_VSS, 0b00000010); // channel 9
SetChanADC(ADC_CH9);
ConvertADC(); // Start conversion
while(BusyADC()); // Wait for completion
return ReadADC(); // Read result
}
and myReadADC2(), that implements manual read from the port.
int myReadADC2() {
int iRet;
OSCCON=0x70; // Select 16 MHz internal clock
ANSEL = 0b00000010; // Set PORT AN9 to analog input
ANSELH = 0; // Set other PORTS as Digital I/O
/* Init ADC */
ADCON0=0b00100101; // ADC port channel 9 (AN9), Enable ADC
ADCON1=0b00000000; // Use Internal Voltage Reference (Vdd and Vss)
ADCON2=0b10101011; // Right justify result, 12 TAD, Select the FRC for 16 MHz
iRet=100;
ADCON0bits.GO=1;
while (ADCON0bits.GO); // Wait conversion done
iRet=ADRESL; // Get the 8 bit LSB result
iRet += (ADRESH << 8); // Get the 2 bit MSB result
return iDelay;
}
Both cases doesn't works, i touch (sending analogic signal) port AN9 but when I set high threshold (~50) led don't blinks, with low threshold (~0) it blinks immidiatly when i provide power to the PIC. Maybe i'm using wrong port? I'm actually passing AN9 as reading port? Or maybe threshold is wrong? How can i found the right value? Thank you
Here the MPLAB C18 Apis http://dl.dropbox.com/u/14663091/API%20microchip%20C18.pdf .
Regarding function myReadADC2(): you need to switch ANSEL and ANSELH configs as RC7/AN9 is configured in bit 1 of ANSELH. Also call me paranoid but for the line
iRet += (ADRESH << 8);
I always like to either save it a temporary variable first or cast explicitly the value ADRESH before shifting it up:
iRet += (((UINT) ADRESH) << 8);
That way I know for sure the bits won't get lost when shifting up which has bitten me before.
Regarding function myReadADC():
OpenADC() only takes two parameters. I presume that bitfield in the third parameter field is for the analog enable (ADRESH/ADRES). I'm assuming that's handled by SetChanADC() but you may have to set ADRESH/ADRES manually. It may help to set a breakpoint in the debugger and stop after configuration is complete to make sure your registers are set appropriatley.

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