Mike,
The data I was receiving for the scratch area was wrong, I tracked it down to the bsf BitCtr,3 in OwReadByte. It failed because Send232 leaves BitCtr containing 1. Took me a while to spot that ,W on the end of it. Shortening the loop makes the timing better anyway.
Mike.
Good catch. One of those darned optimization dependencies. I modified OwReadByte to correct the problem. Program is now 169 bytes.
What do you mean by "shortening the loop makes the timing better"? That Put232 subroutine has perfect 52 usec bit timing with absolutely no jitter. Also wondering why do you need two stop bits?
Ok, here's a revised Put232 routine that leaves BitCtr = 0 on exit and still provides perfect 52 usec timing between bit edges.
Code:; ; 19200 baud, exact 52-usec bit timing (4 MHz) ; Put232 bsf GPIO,RS_Bit ; send start bit movwf OwTemp ; save Tx data movlw 9 ; 8 data bits + 1 stop bit movwf BitCtr ; update bit counter PutBit setc ; shift in stop bits movlw (52-8)/4 ; 52 usecs - 8 usec loop time movwf temp ; a 4 cycle / 4 usec loop decfsz temp,W ; W == 0? yes, skip, else goto $-2 ; loop rrf OwTemp,F ; put data bit in C (W = 0) skpc ; a '1' bit? yes, skip, else iorlw 1<<RS_Bit ; send a '0', W = 1<<RS_Bit movwf GPIO ; send bit, clear OW DataPin decfsz BitCtr,F ; all 9 bits? yes, skip, else goto PutBit ; send next bit retlw 0 ;
Hi mike,
I should have mentioned that I had already moved the setc into the loop to enable it to send two stop bits and so moving the label down one line brought it back to 52 cycles. If I don't send two stop bits then I get corruption in Hyperterminal.
Mike.
Yeah, I should have figured you did that.
Thanks for telling me about how the unused bits behave in the FSR register.
Got the program down to 166 bytes now. I used bit 3 in the BitMask variable for the "conversion complete" flag which leaves BitMask preset to 9 for use as the byte counter in the "Read Scratchpad" section. It saves two bytes. Check it out;
On a newer version of the program I added code to detect DS1820 and DS18S20 devices and to convert their 9 bit temperature word to the DS18B20 12 bit format (1/16th degree resolution);Code:; bcf BitMask,3 ; do "convert" (BitMask=00000001) OwMatch OwReset ; reset all 1-wire devices OwWrite(OwMatchRom) ; send "match rom" command OwWriteBuffer ; send + print rom serial number Send232(' ') ; send <space> char btfsc BitMask,3 ; conversion complete? goto OwScratch ; yes, branch, else OwWrite(OwConvert) ; send "convert" command OwPowerBus ; power OW pin during conversion Send232(0x0D) ; send <cr> char (htab 0) bsf BitMask,3 ; indicate conversion complete goto OwMatch ; do "match rom" for OwScratch OwScratch OwWrite(OwReadScratch) ; send "read scratchpad" command ; movlw 9 ; instructions not needed ; movwf BitMask ; BitMask = 9 already from above RdLoop OwReadByte ; read + print scratchpad byte decfsz BitMask,F ; all 9 bytes read + printed? goto RdLoop ; no, branch, else Send232(0x0D) ; send <cr> char Send232(0x0A) ; send <lf> char goto OwSearchNext ; search and process next device
Now I'm trying to add a sign extended 8x16 multiply routine which will produce a 3 byte sign extended binary result of C° * 1000 (3 decimal places with a value ranging from -55000 to 125000); C° * 1000 = 125 * (Celsius16) / 2Code:OwScratch OwWrite(OwReadScratch) ; send "read scratchpad" command OwReadByte ; read byte 1 movf OwByte,W ; movwf Cels_H ; save temperature hi OwReadByte ; read byte 2 movf OwByte,W ; movwf Cels_L ; save temperature lo movf RomBuffer,W ; get Family ID byte xorlw 0x28 ; is it 12 bit DS18B20? bz OwTemperature ; yes, branch, else OwReadByte ; read byte 3 OwReadByte ; read byte 4 OwReadByte ; read byte 5 OwReadByte ; read byte 6 OwReadByte ; read byte 7, Count_Remain rlf Cels_L,F ; | rlf Cels_H,F ; rlf Cels_L,F ; rlf Cels_H,F ; rlf Cels_L,F ; rlf Cels_H,F ; movlw 0xF0 ; andwf Cels_L,F ; movlw 16 ; movwf temp ; movf OwByte,W ; Count_Remain subwf temp,W ; iorwf Cels_L,F ; now DS18B20 12 bit format OwTemperature
Regards, Mike
Last edited by Mike, K8LH; 23rd January 2009 at 09:41 PM.
Very ingenious, may I suggest you do a multiply by 5 routine (shift left twice and add to original) and call it 3 times as this will keep it in two bytes. I have a Double Dabble routine that will convert it to BCD without the need to do the final multiply by 8. I may have a go at that tomorrow if I get time. The biggest hurdle is RAM.
I had a play with your code and got rid of the sending the ROM serial twice by checking the "conversion complete" flag in the PowerBus code. I had to clear the DataBit but the result was the same length code as the send cr was two location anyway.
BTW, I'm sure you need to subtract 4 (¼°) from your extended result.
Mike.
You mentioned that before and the '1820 Data Sheet also mentions subtracting 0.25 but I haven't quite figured out why.
Printing the rom ID once is a much better way to do it. Let me study that to see if there's a way to reclaim a byte (grin).
Your 3 x 5 x Celsius idea is genius but the product will still require 3 bytes, won't it? I'm starting out with a 12 bit number.
Double-dabble? Sounds familiar. Must check google (grin)...
Mike
Last edited by Mike, K8LH; 22nd January 2009 at 05:07 PM.
I think we can still save one byte while printing the rom ID only once. Program size is now 165 bytes.
Send the <cr> and <lf> newline character pair during the "OwConvert" pass after the OwPowerBus function instead of at the end of the OwMatch code section and print the rom serial number in the OwWriteBuffer function only during the "OwReadScratch" pass.
Code:; bcf BitMask,3 ; do "convert" (BitMask=00000001) OwMatch OwReset ; reset all 1-wire devices OwWrite(OwMatchRom) ; send "match rom" command OwWriteBuffer ; send + print rom serial number btfsc BitMask,3 ; conversion complete? goto OwScratch ; yes, branch, else OwWrite(OwConvert) ; send "convert" command OwPowerBus ; power OW pin during conversion Send232(0x0D) ; send <cr> char Send232(0x0A) ; send <lf> char bsf BitMask,3 ; indicate conversion complete goto OwMatch ; do "match rom" for OwScratch OwScratch OwWrite(OwReadScratch) ; send "read scratchpad" command Send232(' ') ; send space char ; movlw 9 ; instructions not needed ; movwf BitMask ; BitMask = 9 already from above RdLoop OwReadByte ; read + print scratchpad byte decfsz BitMask,F ; all 9 bytes read + printed? goto RdLoop ; no, branch, else goto OwSearchNext ; search and process next deviceCode:OwWriteBuffer macro local loop bcf FSR,3 ; reset FSR = &RomBuffer (0x10) loop movf INDF,W ; call Ow.WriteByte ; send rom serial number byte btfsc BitMask,3 ; OwConvert pass? yes, skip, else call PutHex ; print rom ID byte as hex incf FSR,F ; btfss FSR,3 ; goto loop ; endm
Last edited by Mike, K8LH; 22nd January 2009 at 05:31 PM.
Forget the Double Dabble stuff, I realized that the fractional part can be done by multiplying by 10 and taking the high nibble.
So, calling this 4 times prints the fraction part,
Mike.Code:FracDigit movlw 0x0f andwf TempFrac,F clrc rlf TempFrac,W ;*2 movwf temp rlf temp,W ;*4 addwf TempFrac,F ;*5 rlf TempFrac,F ;*10 swapf TempFrac,W goto PutNybble
Last edited by Pommie; 23rd January 2009 at 09:30 AM.
That routine works extremely well. Bravo!
So, we just need to do an ABS() function, process and print the 3 digit whole number (-55..125), suppress leading zeros (?), print a decimal point, then process and print and the 4 digit fraction. Correct?
Can we do all that with 91 free bytes of memory and our limited RAM resources?
I have not seen this sort of byte hording since collage days. Nice work.
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It's Pommie's fault (grin). He posted this fascinating and clever example of what you can do with only 256 words of program memory and 16 bytes of RAM...Originally Posted by 3v0
Last edited by Mike, K8LH; 23rd January 2009 at 09:59 PM.
Hey, I love to watch this.I may build a few when you get it sorted out.
I have a friend who would like to do some control work but is too tied down with work to get back in to uC's. I would like to drop one of these on his desk and see what happens.
3v0
Last edited by 3v0; 23rd January 2009 at 11:09 PM.
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I've quite enjoyed this little exercise in optimization. When I first wrote this I was just pleased to get the code in 256 words and then Mike came along and demonstrated just how lax I had been with optimization. Along the way I've learnt some very interesting techniques, although they are probably more academic than useful.
Anyway, enough of my ramblings, here's a first go at the full decimal part (7 digits) with absolute and leading zero suppression,
It now occupies 254 words so we have a full word freeCode:OwMatch OwReset ; reset all 1-wire devices OwWrite(OwMatchRom) ; send "match rom" command OwWriteBuffer ; send + print rom serial number btfsc BitMask,2 ; conversion complete? goto OwScratch ; yes, branch, else OwWrite(OwConvert) ; send "convert" command OwPowerBus ; power OW pin during conversion bcf DataBit bsf BitMask,2 ; indicate conversion complete goto OwMatch ; do "match rom" for OwScratch OwScratch Send232(' ') ; send <space> char OwWrite(OwReadScratch) ; send "read scratchpad" command OwReadByte movfw OwByte movwf TempLo OwReadByte movfw OwByte movwf TempHi ReadLoop OwReadByte decfsz BitMask,F goto ReadLoop movf RomBuffer,W ; get Family ID byte xorlw 0x28 ; is it 12 bit DS18B20? bz OwTemperature ; yes, branch, else rlf TempLo,F ; | rlf TempHi,F ; rlf TempLo,F ; rlf TempHi,F ; rlf TempLo,F ; rlf TempHi,F ; movlw 0xF0 ; andwf TempLo,F ; movlw 16 ; movwf temp ; movf OwByte,W ; Count_Remain subwf temp,W ; iorwf TempLo,F ; now DS18B20 12 bit format movlw 4 subwf TempLo,F skpc decf TempHi,F OwTemperature OwReadByte OwReadByte Send232 " " btfss TempHi,7 ;is it negative goto NoNegate Send232 '-' ;Send minus sign comf TempLo,F ;and negate temperature comf TempHi,F incfsz TempLo,F goto NoNegate incf TempHi,F NoNegate movfw TempLo ;keep fraction part movwf TempFrac ;and move it to seperate var movlw 0x0f andwf TempHi,F ;move nibbles around so swapf TempLo,F ;that the temperature is andwf TempLo,F ;contained in TempLo swapf TempHi,W iorwf TempLo,F clrf TempHi ;will contain tens digit movlw 0x100-.100 addwf TempLo,W bnc NoHundreds movwf TempLo Send232 '1' bsf BitMask,0 ;no longer suppressing zeros NoHundreds movlw .10 subwf TempLo,F incf TempHi,F bc NoHundreds decfsz TempHi,F ;is it zero goto PrintIt ;no so print it btfss BitMask,0 ;are we suppressing zeros goto SkipZero ;yes so skip it PrintIt movlw '0' addwf TempHi,W ;print 10s digit call Put232 SkipZero movlw '0'+10 addwf TempLo,W call Put232 ;always print units digit Send232 '.' call FracDigit call FracDigit call FracDigit call FracDigit Send232(0x0D) ; send <cr> char Send232(0x0A) ; send <lf> char goto OwSearchNext ; search and process next device FracDigit movlw 0x0f andwf TempFrac,F clrc rlf TempFrac,W ;*2 movwf temp rlf temp,W ;*4 addwf TempFrac,F ;*5 rlf TempFrac,F ;*10 swapf TempFrac,W goto PutNybble
Mike.
P.S. this is what I see in Hyperterminal,
You can see where I hit them (3 sensors) with a freezing spray.
Last edited by Pommie; 24th January 2009 at 06:07 AM.
Excellent work! Incredible work!
I found some 10F206 samples in PDIP-8 package. Can't wait to try this but would like to print leading spaces to align the decimal points.
Mike
