I need three time period for onewire data reading. Without writing any ISR and can I get required time periods by polling M0, M1 and M2 match register interrup flags. Following code is what I am working on and it doesn't work. Is there any missing settings else?
#define Presc 14 //--------------------------16 bit write ---------------------------- void onewire_write(short int bayt, short int data) // 6, 54, 10 { short int count, bits; bits = bayt * 8; #define AB 6 #define BC 60 #define DD 10 #define M0_i 1 // Bit <2:0> <s:r:i> Stop,Reset,Interrupt #define M1_i 1<<3 // Bit <5:3> <s:r:i> " #define M2_irs 7<<6 // Bit <8:6> <s:r:i> " T1PR = Presc; // Prescale 15, 60 MHz CClock, 15 MHz PCLCK T1MR0 = AB; // Wait this long T1MR1 = AB+BC; // Wait this long T1MR2 = AB+BC+DD ; // Wait this long T1MCR = M0_i | M1_i | M2_irs; // Interrupt,stop and reset settings of Match regs T1TCR = 0x02; // Reset timer1 for (count=0; count<bits; ++count) { output_low(); T1TCR = 0x01; // timer1 starts while(!(T1IR & 1)); // Wait for int flag if ( data&1 != 0 ) output_float(); // write 0 or 1 data >>= 1; while(!(T1IR & 2)); // Wait for int flag output_float(); // set 1-wire high again, while(!(T1IR & 4)); // Wait for int flag T1IR = 0x07; // Clear M2, M1, M0 interrupts } }
Sorry, but the time is quite late - 00:40, but a couple of quick notes.
You should really consider doing your shifts using unsigned integers. Shifts with signed negative integers is not so fun because of sign extension. It is better to stay with unsigned data all the way until you have retrieved and combined the full set of bits, and then optionally type cast to a signed value.
Another thing - do consider the value of your comments.
T1MR0 = AA; // Wait this long T1MR1 = AA+EE; // Wait this long T1MR2 = AA+EE+FF ; // Wait this long
"this long" isn't exactly descriptive. Why not describe what you are waiting for in the onewire bit cycle.
It is a great idea to use version control software for your code, allowing you to compare the full set of differences between to versions. That will often answer that magic question of "I don't know what I did, but now it works". If it doesn't, then it's likely that both the old and the new code aren't working, but that one of the versions may seem to work under specific, limited, conditions.
You are at gmt+1, me +2 :)
I will follow your recommendation concerning unsigned integers. Most probably this issue caused me problems.
"// Wait this long" comment is not mine. I found a delay function on the net and modified a bit. Comment comes from that paste :) Function was something like:
void delay_ms(unsigned int msec) { T1TCR = 0x02; // Reset T1MCR = 0x07; // stop, reset and Interrupt T1PR = 15000; T1MR0 = msec; // Wait this long T1TCR = 0x01; // Go while(!(T1IR & 1)); // Wait for int flag T1IR = 0x01; // Clear interrupt }
Comments are very important. I sometimes forgot to modify or update. Due to its little code size, I thougt I understant the lines and functions (I have red also ds18b20 datasheet and grasped most parts) and left modification after finishing the code. You are right, if I request help from others, first I have to give descriptions, comments etc.
For the version control, sometimes I did it in very primitive way (daily or after some succes I get compressed back up and name it in a descriptive way). For an hobbyist like me, I think it is acceptable :)
Yes, I'm at GMT+1 (Sweden).
Don't do zip files. Hobbyist or professional doesn't much matter. The problems to solve is the same. Basically - what code constitutes a specific version? What was changed between two versions? What may be the reason that two versions behaves differently?
There are many free solutions available. Why not try a CVSNT repository? Works fine on a Windows machine, and since the repository is just text files, a bad disk accident still makes it possible to extract information from whatever files or disk sectors that did survive.
Dear Westermark, I have no previous CVS experience. I have just downloaded a free version, not yet installed. I will try. Thanks ... (PS:I am from Turkiye.)