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bulut_01
Joined: 24 Feb 2024
Posts: 206
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 Posted: Sun Feb 09, 2025 12:01 pm |
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| PrinceNai wrote: | | Quote: | | you must have thought we were amateurs |
No, I don't :-). But since you are a bit on the stiff side with the information, I must ask. Must is a bit strong word, at this point I simply want to, because it really interests me. You mentioned all zeroes in the buffer. Fine. Does your code ever reach the point where it must write a one there? Does it increment counters, at least two of them? How can I know that without asking you? I have no idea about the equipment you use, save for the analyzer and the programming software. What are you debugging with? How? You never say: I did this, I tried that. Result is this. I know that my setup works. And it didn't work off the bat, far from it. But I went step by step. There is a diode blinking, so I know my PIC is alive. There was a breakpoint sitting in the first two states so I knew I could catch the preamble every time. Only after that I went to the decoding part. Drew a diagram of one byte and worked out the timings. Catching my own errors, both in code and in mental process. I prove to myself every time that the code does what you write, not what you think it should do. Those two things are seldom the same at the start.
Anyway, I was tinkering with the code since the version posted previously, so this is the last version:
Receiving part:
| Code: |
#include <18F46K22.h>
#device ADC=10
#FUSES NOWDT //No Watch Dog Timer
#FUSES NOPUT
#device ICD=TRUE
#use delay(internal = 32000000)
/////////////////////////// DEFINES /////////////////////////////////
#define NUMBER_OF_BYTES 7 // number of DECODED bytes to receive
#define TE 640 // duration of one bit in us, change as needed
#define PREAMBLE_MAX_TIME 8*TE
#define PREAMBLE_MIN_TIME 6*TE // we expect a 7 bit preamble, make some room for clock error
#define TRANSITION_MIN_TIME 1.5*TE // same here when sampling
#define TRANSITION_MAX_TIME 2.5*TE
////////////////////////// VARIABLES ////////////////////////////////
char DecodedInputData[10]; // buffer for decoded data
char CurrentByte = 0;
int8 InputByteCounter = 0; // keeps track about which byte we are filling in
int8 BitPosition = 0; // bit position of the incoming data
int8 Have_Data = 0; // flag to inform main data was received and decoded
// switch
enum {GotRisingEdge = 1, GotFallingEdge, SampleData}; // state machine switch
int8 DecodeSwitch = GotRisingEdge;
// Timer
int16 TimerValue;
int8 TMR0_Overflow = 0; // how many times TMR0 has overflowed
////////////////////////// FUNCTIONS ////////////////////////////////
#bit INTDEG = getenv("BIT:INTCON2.INTEDG0") // declare edge selection bit for INT_EXT. INTDEG is a generic name (some PIC's have more than one of those registers,
void ToggleIntEdge (void){ // 18f46k22 has INTDEG0, for example) for external interrupt on Pin_B0. Change this for the PIC you use
if(INTDEG == 1){ // check which edge is currently selected
INTDEG = 0; // activate interrupt on falling edge
}
else{
INTDEG = 1; // activate interrupt on rising edge
}
}
// ------------------------------------------------------------------
void ClearBuffer (void){
DecodedInputData[0] = 0x00; // lazy :-)
DecodedInputData[1] = 0x00;
DecodedInputData[2] = 0x00;
DecodedInputData[3] = 0x00; // lazy :-)
DecodedInputData[4] = 0x00;
DecodedInputData[5] = 0x00;
DecodedInputData[6] = 0x00;
DecodedInputData[7] = 0x00;
DecodedInputData[8] = 0x00;
DecodedInputData[9] = 0x00;
}
//////////////////////// END OF FUNCTIONS //////////////////////////
// ******************************************************************
// INTERRUPTS
// ******************************************************************
#INT_TIMER0
void TIMER0_isr(void)
{
TMR0_Overflow++; // count timer TMR0_Overflows
}
// ------------------------------------------------------------------
#INT_EXT
void EXT_isr(void)
{
clear_interrupt(INT_EXT); // clear interrupt, needed for this particular interrupt type or you come back straight away
//default handling, check if switch variable is out of usefull bounds
if (DecodeSwitch < 1 || DecodeSwitch > 3)
{
// printf("Default handling, testval is out of bounds, DecodeSwitch == %u\r\n", DecodeSwitch);
continue; // Miss switch. The continue statement causes the next iteration of the enclosing loop(While, For, Do) to begin.
}
// ******************************************************************
// ******************************************************************
switch (DecodeSwitch) // state machine used to receive and decode Mancester encoded data
{
// ------------------------------------------------------------------
// wait for a rising edge on the input, this state also serves as a reset. Always come here with L_TO_H transition set (maybe not even needed)!
case GotRisingEdge: // we have a rising edge, could be start of the preamble
{
set_timer0(0); // reset timer
TMR0_Overflow = 0; // and various counters
BitPosition = 0;
InputByteCounter = 0;
CurrentByte = 0;
Have_Data = 0; // and flags
ext_int_edge(0, H_TO_L); // change direction of the interrupt to falling edge
DecodeSwitch = GotFallingEdge; // and go to GotFallingEdge to see if we have a preamble
break;
}
// ------------------------------------------------------------------
case GotFallingEdge: // we have a falling edge, pulse ended. Might be preamble.
{
ext_int_edge(0, L_TO_H); // prepare next interrupt on a rising edge
TimerValue = get_timer0(); // check the time that elapsed between two interrupts
if(TMR0_Overflow == 0 && TimerValue > PREAMBLE_MIN_TIME && TimerValue < PREAMBLE_MAX_TIME) { // bingo, time is good, we have a preamble
set_timer0(0); // preset timer for next measurement
TMR0_Overflow = 0;
DecodeSwitch = SampleData; // and go sample the input
}
else{ // not good, pulse was either too short or too long for a preamble.
DecodeSwitch = GotRisingEdge; // Reset state machine
}
break;
}
// ------------------------------------------------------------------
// We are looking for a transition that in Mancester coding always exist in the middle of a symbol,
// so the sampling is done every 2TE. That can be on the first or second following interrupt,
// depending on whether two subsequent symbols have the same or different value.
// We are using TMR0 value to find if it is time to sample. If it is, sample the input and store
// to the correct location in the data buffer.
// The word symbol means a 2-bit pair that represents either a 1 or a 0.
case SampleData:
{
ToggleIntEdge(); // change the active edge of the interrupt for the next one,
// because transition can be either 0-1 or 1-0, but hardly
// 0-0 or 1-1
TimerValue = get_timer0();
// If this interrupt occured in a time frame from 0,5*TE to 1,5*TE, this symbol has the same
// value as the previous, meanng that interrupt occured also at the start of the symbol, not only in the middle.
// So we need to wait for the next interrupt that will come at the middle of a symbol to actually sample data
// Time between two edges is correct, read input state. This test is intentionally put in the first place
// so it gets serviced first, since the timer is already running for the next symbol
if(TMR0_Overflow == 0 && TimerValue >= TRANSITION_MIN_TIME && TimerValue <= TRANSITION_MAX_TIME){ // this is the one we are looking for, sample and store the data
set_timer0(0); // reset timer for the next symbol
// INVERT THE DECODING LOGIC AS NEEDED HERE!!!!! COMMENT THE WRONG IF OUT!!!! LIKE THIS WORKS FOR IEEE 802 CODING, 01 IS 1, 10 IS 0
// if(input_state(pin_B0) == 0){
if(input_state(pin_B0) == 1){
bit_set(CurrentByte, 7 - BitPosition); // Sample input. Set appropriate bit if needed, leave 0 otherwise
} //
BitPosition++;
if(BitPosition > 7){ // one byte of data was received
BitPosition = 0;
DecodedInputData[InputByteCounter] = CurrentByte; // store that data into the buffer
CurrentByte = 0; // prepare variable for next byte (all zeroes, since we are only setting the bits needed)
InputByteCounter++; // increment byte counter for a correct position in the buffer
if (InputByteCounter == NUMBER_OF_BYTES){ // if all the bytes are in the buffer, reception is done
ext_int_edge(0, L_TO_H);
Have_Data = 1; // we have data, signal that to main
DecodeSwitch = GotRisingEdge; // and reset state machine for the next reception
} // if byte counter
} // if bit position
} // end sampling
// time between two edges is too short for sampling, it may be transition between two symbols with the same value
else if(TMR0_Overflow == 0 && TimerValue < TRANSITION_MIN_TIME){ // the transition came too soon for sampling, exit interrupt but leave
delay_cycles(1); // the timer running and stay in the same case
}
// time between two edges to long for a valid symbol, reset
else{ // time between two transitions was too long,
ext_int_edge(0, L_TO_H);
DecodeSwitch = GotRisingEdge; // reset state machine
}
break;
} // end case
} // end switch
} // end interrupt
// ******************************************************************
// END OF INTERRUPTS
// ******************************************************************
void main()
{
ClearBuffer(); // clear receiving buffer
setup_timer_0(RTCC_INTERNAL|RTCC_DIV_8); // 65.535us, resolution 1us. RESOLUTION MUST BE 1us!!!!
clear_interrupt(INT_EXT);
ext_int_edge(0,L_TO_H);
enable_interrupts(INT_EXT);
enable_interrupts(INT_TIMER0);
enable_interrupts(GLOBAL);
while(TRUE)
{
if(Have_Data == 1){
Have_Data = 0; // do something with data
}
}
}
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16F1824 register not
| Code: | | #bit INTDEG = getenv("BIT:INTCON2.INTEDG0") |
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PrinceNai
Joined: 31 Oct 2016
Posts: 527
Location: Montenegro
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| Posted: Sun Feb 09, 2025 12:17 pm |
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It can't, that is where this bit is located on 18f46k22. I wrote in one of the previous posts that you'll have to find that bit for your PIC. Yours is in the OPTION_REG, bit 6. Page 176 of datasheet.
So: #bit INTDEG = getenv("BIT:OPTION_REG.INTEDG")
I just noticed there is a typo in my program here (should be #bit INTEDG). Use this the way it is written here. |
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temtronic
Joined: 01 Jul 2010
Posts: 9426
Location: Greensville,Ontario
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| Posted: Sun Feb 09, 2025 12:56 pm |
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CURIOUS... I see ICD=TRUE....
Is there a possibility that that can cause problems ? I've never used it but know that building in 'debug' and trying to run in the Real World doesn't work. |
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PrinceNai
Joined: 31 Oct 2016
Posts: 527
Location: Montenegro
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| Posted: Sun Feb 09, 2025 1:07 pm |
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Never had a problem or noticed any difference so far. I also never checked if the .hex is different with that option enabled. Did a quick build with it turned off now and the .hex size stays the same.
In this particular case the receiving PIC is in debug mode for testing purposes. |
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bulut_01
Joined: 24 Feb 2024
Posts: 206
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| Posted: Sun Feb 09, 2025 2:47 pm |
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| PrinceNai wrote: | Never had a problem or noticed any difference so far. I also never checked if the .hex is different with that option enabled. Did a quick build with it turned off now and the .hex size stays the same.
In this particular case the receiving PIC is in debug mode for testing purposes. |
What hardware do you use to debug? Pickit 3 or icd3 |
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PrinceNai
Joined: 31 Oct 2016
Posts: 527
Location: Montenegro
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| Posted: Sun Feb 09, 2025 3:10 pm |
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Pickit3.
Below is the comparison between two streams you sent, 44 and 55. Green portions were the same for both.
https://ibb.co/B2MpDfh0 |
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bulut_01
Joined: 24 Feb 2024
Posts: 206
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| Posted: Wed Feb 12, 2025 6:08 am |
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| PrinceNai wrote: | Pickit3.
Below is the comparison between two streams you sent, 44 and 55. Green portions were the same for both.
https://ibb.co/B2MpDfh0 |
Your code is not working. The reason is that all timers in 16f1824 are not overflowed by 1 us. When I debug, timer0 is overflowed by 32 us. You need to edit your code according to the timer overflow of 32 us. |
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temtronic
Joined: 01 Jul 2010
Posts: 9426
Location: Greensville,Ontario
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| Posted: Wed Feb 12, 2025 6:57 am |
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| Please post your latest code |
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bulut_01
Joined: 24 Feb 2024
Posts: 206
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| Posted: Wed Feb 12, 2025 7:08 am |
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| temtronic wrote: | | Please post your latest code |
Last edited by bulut_01 on Mon Feb 24, 2025 1:43 pm; edited 1 time in total |
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PrinceNai
Joined: 31 Oct 2016
Posts: 527
Location: Montenegro
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| Posted: Wed Feb 12, 2025 7:47 am |
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| Code: | | setup_timer_0(RTCC_INTERNAL|RTCC_DIV_1); |
will not produce 1us Timer0 step with 32MHz clock. Check Timer0 setup in my code. |
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temtronic
Joined: 01 Jul 2010
Posts: 9426
Location: Greensville,Ontario
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| Posted: Wed Feb 12, 2025 8:03 am |
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clock is 32Mhz
input to Timer0 is Fosc/4, so 32/4 = 8Mhz
Timer0 prescaler is '1' , so /2 = 4Mhz
1/4,000,000 = .00000025
not to sure how you calculate 32 useconds
Last edited by temtronic on Wed Feb 12, 2025 8:06 am; edited 1 time in total |
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bulut_01
Joined: 24 Feb 2024
Posts: 206
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| Posted: Wed Feb 12, 2025 8:06 am |
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| PrinceNai wrote: | | Code: | | setup_timer_0(RTCC_INTERNAL|RTCC_DIV_1); |
will not produce 1us Timer0 step with 32MHz clock. Check Timer0 setup in my code. |
Your code is exactly the same, where do I check? |
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bulut_01
Joined: 24 Feb 2024
Posts: 206
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| Posted: Wed Feb 12, 2025 8:09 am |
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| PrinceNai wrote: | | Code: | | setup_timer_0(RTCC_INTERNAL|RTCC_DIV_1); |
will not produce 1us Timer0 step with 32MHz clock. Check Timer0 setup in my code. |
16f1824 timer0 is 8 bit. you need 16 bit counter timer1 is 16 bit. 1 us overfloaw does not work |
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temtronic
Joined: 01 Jul 2010
Posts: 9426
Location: Greensville,Ontario
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| Posted: Wed Feb 12, 2025 8:15 am |
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so you have to change to another timer !!!
you have timers 1, 2 4, 6 on the t PIC with 16 bit counters.... |
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PrinceNai
Joined: 31 Oct 2016
Posts: 527
Location: Montenegro
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| Posted: Wed Feb 12, 2025 8:16 am |
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| Then use Timer1. Change all references from Timer0 to Timer1. Mind you, overflow isn't 1us. Timer increments by 1 in 1us. Overflow is 65ms |
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