RobG 1,892 Posted July 3, 2011 Share Posted July 3, 2011 EDIT: the final versions of converter are hereUntil now, I could get away with wasting clock cycles in my code.My current project however requires from me writing efficient code and saving every possible clock cycle that I can.I started to optimize my code with binary to decimal conversion piece.My usual way of doing conversion, modulus + division, is the easiest but at the same time most clock cycle consuming method.I found few suggestions on the net, like using C's div function, which returns structure with quotient and remainder eliminating the need for modulus operation.Another way of converting I found is to use shifts and additions, much faster, but there is still room for improvement.I figured to get better results, I will need to use some hardware feature, but the value line does not come with MPY module. There's one instruction that can help speed up decimal conversion, not available in C directly, but available through intrinsic function or asm. I decided to give it a try and the results are very positive.I created 5 different functions to convert 10 bit(ADC's resolution) binary into an array of decimal numbers.The range is 0-999 and there's no logic to handle overflow (10 bits range is 0-1023,) I didn't want to complicate this for testing purposes.Here are the results (clock cycles) for the numbers 9, 99, and 999: 1. Modulus+divide ----- 346 - 657 - 973 2. C's div ------------ 293 - 575 - 886 3. Shift+add ---------- 248 - 274 - 327 4. S+a with my mods --- 139 - 233 - 234 5. My converter ------- 133 - 141 - 162 6. My conv with cond -- 98 -- 134 - 193 Shift and add becomes slow when binary > 9. It is also limited, adding 4th digit or increasing the number of binary bits would affect the performance. This is true for modulus+divide method as well, but updating it for higher bit number is pretty easy.The thing about my converter is that it produces BCD integer which then is converted into an array. If you don't need an array, you can save another 41 cycles! Expanding it to 12 or 16 bits would have little effect on performance in comparison with other methods. Using conditionals speeds up conversion of small numbers by about 25%, but it slows down conversion of large numbers by about 20% (10 bit conversion.) And there is still room for improvement, it can be re-written in asm.#include "msp430g2231.h" #include void modAndDiv(unsigned int n); void modAndDivAlt(unsigned int n); void versionOfHackersDelight(unsigned int n); unsigned int decimalAdd(unsigned int n); unsigned int decimalAddAlt(unsigned int n); unsigned char decimalResults[3] = {0,0,0}; void main(void) { WDTCTL = WDTPW + WDTHOLD; unsigned int result; //BCD result = decimalAdd(999); //121 decimalResults[2] = result & 0x000F;//8 decimalResults[1] = (result & 0x00F0)>>4;//24 decimalResults[0] = (result & 0x0F00)>>8;//9 //total 162 result = decimalAdd(99);//100 decimalResults[2] = result & 0x000F;//8 decimalResults[1] = (result & 0x00F0)>>4;//24 decimalResults[0] = (result & 0x0F00)>>8;//9 //total 141 result = decimalAdd(9);//92 decimalResults[2] = result & 0x000F;//8 decimalResults[1] = (result & 0x00F0)>>4;//24 decimalResults[0] = (result & 0x0F00)>>8;//9 //total 133 result = decimalAddAlt(999); //152 decimalResults[2] = result & 0x000F;//8 decimalResults[1] = (result & 0x00F0)>>4;//24 decimalResults[0] = (result & 0x0F00)>>8;//9 //total 193 result = decimalAddAlt(99);//93 decimalResults[2] = result & 0x000F;//8 decimalResults[1] = (result & 0x00F0)>>4;//24 decimalResults[0] = (result & 0x0F00)>>8;//9 //total 134 result = decimalAddAlt(9);//57 decimalResults[2] = result & 0x000F;//8 decimalResults[1] = (result & 0x00F0)>>4;//24 decimalResults[0] = (result & 0x0F00)>>8;//9 //total 98 modAndDiv(999); //total 973 modAndDiv(99); //total 657 modAndDiv(9); //total 346 modAndDivAlt(999); //total 886 modAndDivAlt(99); //total 575 modAndDivAlt(9); //total 293 versionOfHackersDelight(999); //total 234 (original 327) versionOfHackersDelight(99); //total 233 (original 274) versionOfHackersDelight(9); //total 139 (original 248) } unsigned int decimalAdd(unsigned int n) { unsigned int result = 0; result = _bcd_add_short(result, (n & 0x0007)); if(n & 0x0008) result = _bcd_add_short(result, 0x0008); if(n & 0x0010) result = _bcd_add_short(result, 0x0016); if(n & 0x0020) result = _bcd_add_short(result, 0x0032); if(n & 0x0040) result = _bcd_add_short(result, 0x0064); if(n & 0x0080) result = _bcd_add_short(result, 0x0128); if(n & 0x0100) result = _bcd_add_short(result, 0x0256); if(n & 0x0200) result = _bcd_add_short(result, 0x0512); return result; } void modAndDiv(unsigned int n) { decimalResults[0] = 0; decimalResults[1] = 0; decimalResults[2] = 0; unsigned char charIndex = 2; while(n > 0) { decimalResults[charIndex] = n % 10; n /= 10; charIndex--; } } void modAndDivAlt(unsigned int n) { decimalResults[0] = 0; decimalResults[1] = 0; decimalResults[2] = 0; unsigned char charIndex = 2; div_t d; while(n > 0) { d = div(n,10); decimalResults[charIndex] = d.rem; n= d.quot; charIndex--; } } void versionOfHackersDelight(unsigned int n) { static const unsigned int rem[12] = { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 0, 1 }; unsigned int q1, q2, q3, q, r; decimalResults[0] = 0; decimalResults[1] = 0; decimalResults[2] = 0; q1 = (n >> 1) + (n >> 2); q1 += q1 >> 4; q1 += q1 >> 8; q2 = q1 >> 3; r = n - ((q2 << 3) + q2 + q2); // originally r = n - q2 * 10; q = q2 + (r > 9); decimalResults[2] = rem[r]; if(n<10) // added this condition to exit when n<10, following calculations are just a waste return; q3 = (q >> 1) + (q >> 2); q3 += q3 >> 4; q3 = q3 >> 3; r = q - ((q3 << 3) + q3 + q3); // originally r = q - q3 * 10; decimalResults[0] = q3 + (r > 9); decimalResults[1] = rem[r]; } unsigned int decimalAddAlt(unsigned int n) { unsigned int result = 0; result = _bcd_add_short(result, (n & 0x0007)); if(n & 0x0008) { result = _bcd_add_short(result, 0x0008); if(n<16) return result; } if(n & 0x0010) { result = _bcd_add_short(result, 0x0016); if(n<32) return result; } if(n & 0x0020) { result = _bcd_add_short(result, 0x0032); if(n<64) return result; } if(n & 0x0040) { result = _bcd_add_short(result, 0x0064); if(n<128) return result; } if(n & 0x0080) { result = _bcd_add_short(result, 0x0128); if(n<256) return result; } if(n & 0x0100) { result = _bcd_add_short(result, 0x0256); if(n<512) return result; } if(n & 0x0200) result = _bcd_add_short(result, 0x0512); return result; } Here's the actual binary to BCD converter, both versions:result = convertToBinary(binary); result = convertToBinaryAlt(binary); decimalResults[3] = result & 0x000F; decimalResults[2] = (result & 0x00F0)>>4; decimalResults[1] = (result & 0x0F00)>>8; decimalResults[0] = (result & 0xF000)>>12; unsigned int convertToBinary(unsigned int n) { unsigned int result = 0; result = _bcd_add_short(result, (n & 0x0007)); if(n & 0x0008) result = _bcd_add_short(result, 0x0008); if(n & 0x0010) result = _bcd_add_short(result, 0x0016); if(n & 0x0020) result = _bcd_add_short(result, 0x0032); if(n & 0x0040) result = _bcd_add_short(result, 0x0064); if(n & 0x0080) result = _bcd_add_short(result, 0x0128); if(n & 0x0100) result = _bcd_add_short(result, 0x0256); if(n & 0x0200) result = _bcd_add_short(result, 0x0512); return result; } //alternate version with conditionals unsigned int convertToBinaryAlt(unsigned int n) { unsigned int result = 0; result = _bcd_add_short(result, (n & 0x0007)); if(n & 0x0008) { result = _bcd_add_short(result, 0x0008); if(n<16) return result; } if(n & 0x0010) { result = _bcd_add_short(result, 0x0016); if(n<32) return result; } if(n & 0x0020) { result = _bcd_add_short(result, 0x0032); if(n<64) return result; } if(n & 0x0040) { result = _bcd_add_short(result, 0x0064); if(n<128) return result; } if(n & 0x0080) { result = _bcd_add_short(result, 0x0128); if(n<256) return result; } if(n & 0x0100) { result = _bcd_add_short(result, 0x0256); if(n<512) return result; } if(n & 0x0200) result = _bcd_add_short(result, 0x0512); return result; } Quote Link to post Share on other sites

nobody 47 Posted July 3, 2011 Share Posted July 3, 2011 If you have enough free flash, try using conversion tables (fully or partially). This is the fastest method. Quote Link to post Share on other sites

oPossum 1,083 Posted July 3, 2011 Share Posted July 3, 2011 ; ; Convert 16 bit binary to 24 bit packed BCD ; C prototype: unsigned long bin2bcd(unsigned x) ; clr R13 clr R14 swpb R12 tst.b R12 jz lsb swpb R12 rla R12 dadd R14, R14 rla R12 dadd R14, R14 rla R12 dadd R14, R14 rla R12 dadd R14, R14 rla R12 dadd R14, R14 rla R12 dadd R14, R14 rla R12 dadd R14, R14 rla R12 dadd R14, R14 lsb rla R12 dadd R14, R14 rla R12 dadd R14, R14 rla R12 dadd R14, R14 rla R12 dadd R14, R14 rla R12 dadd R14, R14 rla R12 dadd R14, R14 dadd R13, R13 rla R12 dadd R14, R14 dadd R13, R13 rla R12 dadd R14, R14 dadd R13, R13 mov R14, R12 ret RobG 1 Quote Link to post Share on other sites

RobG 1,892 Posted July 3, 2011 Author Share Posted July 3, 2011 This is very nice oPossum, so we are now down to 85, 85, and 102 clock cycles (44 conversion + 41 array, 44 + 41, 61 + 41.) Quote Link to post Share on other sites

oPossum 1,083 Posted July 3, 2011 Share Posted July 3, 2011 Test case and commented code for binary to packed BCD and binary to unpacked BCD This could be tweaked for 3 or 4 digits if you really need maximum speed and compactness. #include "msp430g2211.h" unsigned long bin2pbcd(unsigned bin); // Binary to packed BCD void bin2bcd(unsigned bin, char * bcd); // Binary to unpacked BCD int main(void) { unsigned long pbcd; char bcd[5]; WDTCTL = WDTPW + WDTHOLD; // Stop watchdog timer pbcd = bin2pbcd(0); // 43 cycles pbcd = bin2pbcd(1); // 43 cycles pbcd = bin2pbcd(9); // 44 cycles pbcd = bin2pbcd(99); // 44 cycles pbcd = bin2pbcd(999); // 61 cycles pbcd = bin2pbcd(9999); // 61 cycles pbcd = bin2pbcd(65535); // 60 cycles bin2bcd(0, bcd); // 77 cycles bin2bcd(1, bcd); // 77 cycles bin2bcd(9, bcd); // 78 cycles bin2bcd(99, bcd); // 78 cycles bin2bcd(999, bcd); // 95 cycles bin2bcd(9999, bcd); // 95 cycles bin2bcd(12345, bcd); // 95 cycles bin2bcd(54321, bcd); // 95 cycles bin2bcd(65535, bcd); // 94 cycles } ; bin2bcd.asm .cdecls C, LIST, "msp430g2211.h" ; Include device header file .text .global bin2pbcd .global bin2bcd ; ; Convert 16 bit binary to 20 bit packed BCD ; C prototype: unsigned long bin2pbcd(unsigned bin) ; bin2pbcd clr R13 ; Clear BCD result clr R14 ; swpb R12 ; Swap upper/lower byte tst.b R12 ; Check if upper byte is zero jz lsb ; Yes, skip upper byte swpb R12 ; Sway upper/lower bytes back rla R12 ; Test msb of binary dadd R14, R14 ; Multiply BCD by 2 and add binary bit rla R12 ; Test bit 14 of binary dadd R14, R14 ; Multiply BCD by 2 and add binary bit rla R12 ; Test bit 13 of binary dadd R14, R14 ; Multiply BCD by 2 and add binary bit rla R12 ; Test bit 12 of binary dadd R14, R14 ; Multiply BCD by 2 and add binary bit rla R12 ; Test bit 11 of binary dadd R14, R14 ; Multiply BCD by 2 and add binary bit rla R12 ; Test bit 10 of binary dadd R14, R14 ; Multiply BCD by 2 and add binary bit rla R12 ; Test bit 9 of binary dadd R14, R14 ; Multiply BCD by 2 and add binary bit rla R12 ; Test bit 8 of binary dadd R14, R14 ; Multiply BCD by 2 and add binary bit lsb rla R12 ; Test bit 7 of binary dadd R14, R14 ; Multiply BCD by 2 and add binary bit rla R12 ; Test bit 6 of binary dadd R14, R14 ; Multiply BCD by 2 and add binary bit rla R12 ; Test bit 5 of binary dadd R14, R14 ; Multiply BCD by 2 and add binary bit rla R12 ; Test bit 4 of binary dadd R14, R14 ; Multiply BCD by 2 and add binary bit rla R12 ; Test bit 3 of binary dadd R14, R14 ; Multiply BCD by 2 and add binary bit rla R12 ; Test bit 2 of binary dadd R14, R14 ; Multiply BCD by 2 and add binary bit dadd R13, R13 ; rla R12 ; Test bit 1 of binary dadd R14, R14 ; Multiply BCD by 2 and add binary bit dadd R13, R13 ; rla R12 ; Test bit 0 of binary dadd R14, R14 ; Multiply BCD by 2 and add binary bit dadd R13, R13 ; mov R14, R12 ; Move LSW in to proper register ret ; Return ; Convert 16 bit binary to 5 characters of BCD ; C prototype: void bin2bcd(unsigned bin, char * bcd) ; bin2bcd mov R13, R15 ; Save BCD pointer call #bin2pbcd ; Convert to packed BCD mov R12, R14 ; Copy digits 2 -> 5 and #0x0F0F, R12 ; Mask digits 3 & 5 mov.b R12, 4(R15) ; Move digit 5 to bcd[4] swpb R12 ; Swap digits 3 & 5 mov.b R12, 2(R15) ; Move digit 3 to bcd[2] rra R14 ; Shift digits 2 & 4 to lower nibble rra R14 ; rra R14 ; rra R14 ; and #0x0F0F, R14 ; Mask digits 2 & 4 mov.b R14, 3(R15) ; Move digit 4 to bcd[3] swpb R14 ; Swap digits 2 & 4 mov.b R14, 1(R15) ; Move digit 2 to bcd[1] mov.b R13, 0(R15) ; Move digit 1 to bcd[0] ret ; Return bluehash and gwdeveloper 2 Quote Link to post Share on other sites

Mac 67 Posted July 3, 2011 Share Posted July 3, 2011 oPossum, This is good stuff. Please keep it coming. Is there a repository of assembly code snippets like this somewhere? You know, like the PIC code repository at PICLIST, but for MSP430? Cheerful regards, Mike Quote Link to post Share on other sites

bluehash 1,581 Posted July 4, 2011 Share Posted July 4, 2011 hmm.. the code vault was meant for that. This way you get support and code, both together. Quote Link to post Share on other sites

Mac 67 Posted July 4, 2011 Share Posted July 4, 2011 hmm.. the code vault was meant for that. This way you get support and code, both together. The oldest post in "the code vault" seems to be from August 2010. Is that when TI came out with the MSP430? Quote Link to post Share on other sites

RobG 1,892 Posted July 4, 2011 Author Share Posted July 4, 2011 Now I am thinking I have approached this all wrong. I wanted to stick with C and that's why I searched for C examples, and that's why I came up with my C routine. Instead, I should have abandoned C all together or at least for the parts that are inefficient and use asm. Quick search on Google and I found what I was looking for (I knew this was done already, just couldn't find it.) slaa151 msp430x11x1_ca_07.s43 and many more, like thermometer code examples ;------------------------------------------------------------------------------ bin2bcd; Subroutine for converting 16 bit binary to BCD ; Input: R12 is 16 bit binary ; Working: R15 is used and not saved ; Output: R14|R13 5 digit BCD ;------------------------------------------------------------------------------ mov #16,R15 clr R14 clr R13 L$1 rla R12 dadd R13,R13 dadd R14,R14 dec R15 jnz L$1 ret Since loops are used, this is not the most efficient code but it's not that bad, and it is very close in efficiency to my C routine. That said, those who do not want to use asm, use my routine, it's the fastest I know of written in C. @Mac and bluehash, the reason for this thread in Code Vault is just that, share the code Quote Link to post Share on other sites

Mac 67 Posted July 4, 2011 Share Posted July 4, 2011 ... @Mac and bluehash, the reason for this thread in Code Vault is just that, share the code The emphasis (in code vault) seems to be C and there's nothing here more than a year old. I'm looking for assembly language examples like the program listing you found which was dated February 2005. Thanks for posting, btw... You should recognize oPossum's code as an "unrolled" and optimized version of the loop routine you posted. Just for fun, I rolled it back up into a loop to characterize a four digit (0..9999) version yesterday; ; ; bin2bcd, 16 bit binary to 4 digit packed bcd (0..9999) ; clr.w R14 ; 8 words, 83 cycles mov.w #1, R13 ; (1) xlp rla.w R12 ; (1) dadd.w R14, R14 ; (1) rla.w R13 ; (1) jnz xlp ; (2) mov.w R14, R12 ; return pbcd in R12 (2) Cheerful regards, Mike McLaren, K8LH oPossum 1 Quote Link to post Share on other sites

bluehash 1,581 Posted July 4, 2011 Share Posted July 4, 2011 hmm.. the code vault was meant for that. This way you get support and code, both together. The oldest post in "the code vault" seems to be from August 2010. Is that when TI came out with the MSP430? Yes. But TI came out with the MSP430 much earlier. 43oh was created when the Launchpad was released as there were alot of questions floating on the web unanswered. The only places where you will find code for the MSP430 arch is the TI web site or here. The TI site is a very good repository of code, but strewed all across the site and do not come up in searches. You are free to post anything interesting you find on the TI site, here. Quote Link to post Share on other sites

RobG 1,892 Posted July 4, 2011 Author Share Posted July 4, 2011 ... @Mac and bluehash, the reason for this thread in Code Vault is just that, share the code The emphasis (in code vault) seems to be C and there's nothing here more than a year old. I'm looking for assembly language examples like the program listing you found which was dated February 2005. Thanks for posting, btw... Well, here's our chance to start one Quote Link to post Share on other sites

Mac 67 Posted July 4, 2011 Share Posted July 4, 2011 Just found a document from 2000, MSP430 Family Mixed-Signal Microcontroller Application Reports (slaa024.pdf), which seems to have a lot of the basic stuff I'm lookin' for (including that 16-bit to 5-digit binary-to-bcd routine). Yippee! Regards, Mike hvontres and zeke 2 Quote Link to post Share on other sites

RobG 1,892 Posted July 4, 2011 Author Share Posted July 4, 2011 Yeah, I came across that one too, it's not only code but also hardware design gold mine. Didn't have time to process that one yet, 1000+ pages of good stuff, like converters, power meters, ADC, PWM, triacs, you name it. I think the link to that document belongs in it's own post. I guess some things are timeless. Quote Link to post Share on other sites

zeke 693 Posted July 4, 2011 Share Posted July 4, 2011 I noticed something interesting in that document. The author keeps saying that the example circuit is for a MSP430C3xx series device. I looked into that and discovered that their input voltage can range between 2.7 and 5.5 Volts. Therefore, the example hardware circuits will need to change to adapt to the lower voltages of the newer devices. Quote Link to post Share on other sites

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