Multiple if then optimization

[Darrel Taylor]

The */ operator first multiplies the 2 values (Uin * 124).
Then it discards the low byte, and returns the rest.
So effectively, it divides the result by 256, without having to do the divide part.

100 / 207 = 0.48309178
124 / 256 = 0.484375 ; not exact, but pretty close

You're correct that there are small differences between the 2 formulas, but the error is less than +/- 1. And, you will never see a difference with the resolution of a 16 block bargraph.

And, there probably is a need to test it.
I was using a 16F877 with a 4x20 LCD. Could have missed something for your 16F628A and 1x16 LCD.
<br>

[Acetronics2]

Hi, Darrel

Could you tell us for LCD Initialization at powerup ...If Uin first value is > 10 ... I do not see any ???

you just suppose exhaust is air filled ???

Alain

[Darrel Taylor]

I'm not sure what you mean Alain.

If the first value is > 10, it will just draw the bargraph like normal.
It doesn't do anything until a serial byte is received.
<br>

[Acetronics2]

I'm not sure what you mean Alain.

If the first value is > 10, it will just draw the bargraph like normal.
It doesn't do anything until a serial byte is received.
<br>

Hi,Darrel

What I ment is you initialize the LCD ... ONLY if the value is < 10 ... ( when writing TOO LOW )

What if you stop the engine and start it again ??? ... first value will be > 10 , due to the exhaust gases still in the exhaust tubing ... and I do not see any LCDOUT $FE,1 in this figure.

Alain

[skimask]

What if you stop the engine and start it again ??? ... first value will be > 10 , due to the exhaust gases still in the exhaust tubing ... and I do not see any LCDOUT $FE,1 in this figure.
Alain

Exhaust gases might still be in the tubing, but I wonder how quickly the sensor will cool off and not make a decent output. In my experience, those things cool off fairly quick. But then again, the 3/4 wire ones heat up pretty fast too...

[Mugelpower]

Hi Guys,

now thats stuff I´m into ! Those lambda probes are reacting pretty fast when hot, about the whole scale from too lean to too rich in half a second . Reliable results will be in after about half a minute with a cold engine starting when using 4 wire probes, 2 minutes or more with one wire probes and those one wire probes without heating are useless for idle control, heats too low. You can see lots of hidden stuff like choke or accelerator pump work or fuel cutoff when stepping off the gas. Funny to watch but most times absolut neccessary for the first setup.

[Darrel Taylor]

What I ment is you initialize the LCD ... ONLY if the value is < 10 ... ( when writing TOO LOW )

What if you stop the engine and start it again ??? ... first value will be > 10 , due to the exhaust gases still in the exhaust tubing ... and I do not see any LCDOUT $FE,1 in this figure.

Oh, you mean the "Clear Screen".
Since it writes to all 16 characters on each pass, I used "Home Cursor" ($FE,2) instead of "Clear Screen" ($FE,1) to prevent blinking of the display during updates.

Or, if you're referring to the Power-On initialization that gets rid of the black blocks and makes the LCD work in the first place .... Mugel didn't have any specific initialization sequences in his original program and reported it to be working. So I assumed his display didn't need it.

The first character sent to the LCD will cause PBP to initialize the display (if it hasn't already). It doesn't have to be $FE,1.
<br>

[paul borgmeier]

A Different Approach (317 Words ... without most of Darrel's amazing methods, which means there is room for more codesavings)

;@__config _XT_OSC & _WDT_ON & _MCLRE_ON & _LVP_OFF & _CP_OFF
CMCON=%00000111
DEFINE DEBUG_BAUD 2400   'Debug baud rate 
DEFINE DEBUGIN_REG PORTB 'Debugin pin port 
DEFINE DEBUGIN_BIT 0     'Debugin pin bit 
DEFINE DEBUGIN_MODE 1    'Debugin mode: 0 = True, 1 = Inverted 

;DEFINE OSC 4

xB0 var byte     ; SERIAL IN IS A BYTE SO MAKE IT A BYTE
;inputData var word ' variable to receive data into

' START OF MAIN PROGRAM
'
CMCON = 7 ' RA0-RA3 are digital I/O
TRISA = 0 ' PORT A is output
TRISB = 1 ' RB0 is Input others output

MAIN:

DEBUGin [xB0]

;B0 = 100 * B0  ; why do these two lines?  B0 is already a Byte so work with Bytes
;Uin = B0 / 207  ;

LCDOUT $FE, 1

If xB0 < 21 then
    LCDOUT "TOO LOW"
    GOTO OUT
ENDIF

IF xB0 < 34 then BARGRAPH1
IF xB0 < 42 then BARGRAPH2
IF xB0 < 52 then BARGRAPH3
IF xB0 < 63 then BARGRAPH4
IF xB0 < 73 then BARGRAPH5
IF xB0 < 92 then BARGRAPH6
IF xB0 < 112 then BARGRAPH7
IF xB0 < 131 then BARGRAPH8

LCDOUt $FE, $C0

IF xB0 < 152 then BARGRAPH9
IF xB0 < 170 then BARGRAPH10
IF xB0 < 181 then BARGRAPH11
IF xB0 < 191 then BARGRAPH12
IF xB0 < 201 then BARGRAPH13
IF xB0 < 210 then BARGRAPH14
IF xB0 < 220 then BARGRAPH15
IF xB0 < 230 then BARGRAPH16

LCDOUT $FE,$C0,"TOO RICH"

goto OUT

BARGRAPH16:
gosub p255
BARGRAPH15:
gosub p255
BARGRAPH14:
gosub p255
BARGRAPH13:
gosub p255
BARGRAPH12:
gosub p255
BARGRAPH11:
gosub p255
BARGRAPH10:
gosub p255
BARGRAPH9:
gosub p255

LCDOUT $FE, $80   ; line 1

BARGRAPH8:
gosub p255
BARGRAPH7:
gosub p255
BARGRAPH6:
gosub p255
BARGRAPH5:
gosub p255
BARGRAPH4:
gosub p255
BARGRAPH3:
gosub p255
BARGRAPH2:
gosub p255
BARGRAPH1:
gosub p255

OUT: 
Pause 5
goto MAIN

p255:
lcdout 255
return


END ' End of program

[disclaimer] untested [/disclaimer]

[Darrel Taylor]

Good one Paul.

Completely different way, and saved 18 words.

And you're right. The multiplication uses a lot of code space.
So I thought I'd remove it from my last version too and see what happened.

268 words

<font color="#000000"><b>CMCON </b>= <font color="#800000"><b>7                </b></font><font color="#0000FF"><b><i>' Disable Comparators

</i></b></font><font color="#008000"><b>DEFINE </b></font><b>DEBUG_BAUD </b><font color="#800000"><b>2400   </b></font><font color="#0000FF"><b><i>'Debug baud rate 
</i></b></font><font color="#008000"><b>DEFINE </b></font><b>DEBUGIN_REG PORTB </b><font color="#0000FF"><b><i>'Debugin pin port 
</i></b></font><font color="#008000"><b>DEFINE </b></font><b>DEBUGIN_BIT </b><font color="#800000"><b>0     </b></font><font color="#0000FF"><b><i>'Debugin pin bit 
</i></b></font><font color="#008000"><b>DEFINE </b></font><b>DEBUGIN_MODE </b><font color="#800000"><b>1    </b></font><font color="#0000FF"><b><i>'Debugin mode: 0 = True, 1 = Inverted 

</i></b></font><b>Uin       </b><font color="#008000"><b>VAR BYTE
</b></font><b>B0        </b><font color="#008000"><b>VAR BYTE 
</b></font><b>BarCount  </b><font color="#008000"><b>VAR BYTE
</b></font><b>BarValue  </b><font color="#008000"><b>VAR WORD
</b></font><b>MsgAddr   </b><font color="#008000"><b>VAR WORD
</b></font><b>Carry     </b><font color="#008000"><b>VAR </b></font><b>STATUS</b>.<font color="#800000"><b>0        </b></font><font color="#0000FF"><b><i>; Hardware carry flag

</i></b></font><font color="#008000"><b>GOTO </b></font><b>Main                     </b><font color="#0000FF"><b><i>; Jump over data
;=============================================================================
 </i></b></font><b>BarSteps</b>:  <b>POKECODE   </b><font color="#800000"><b>22</b></font>,<font color="#800000"><b>33</b></font>,<font color="#800000"><b>41</b></font>,<font color="#800000"><b>51</b></font>,<font color="#800000"><b>62</b></font>,<font color="#800000"><b>72</b></font>,<font color="#800000"><b>91</b></font>,<font color="#800000"><b>111</b></font>,<font color="#800000"><b>130</b></font>,<font color="#800000"><b>151</b></font>,<font color="#800000"><b>169</b></font>,<font color="#800000"><b>180</b></font>,<font color="#800000"><b>190</b></font>,<font color="#800000"><b>200</b></font>,<font color="#800000"><b>209</b></font>,<font color="#800000"><b>219
</b></font><b>_BarSteps   </b><font color="#008000"><b>CON </b></font><b>EXT           </b><font color="#0000FF"><b><i>; create a PBP constant that points to the Table

 </i></b></font><b>TooLow</b>:  <b>POKECODE </b><font color="#800000"><b>$FE</b></font>,<font color="#800000"><b>1</b></font>,<font color="#FF0000">&quot;TOO LOW &quot;</font>,<font color="#800000"><b>0
</b></font><b>_TooLow   </b><font color="#008000"><b>CON </b></font><b>EXT             </b><font color="#0000FF"><b><i>; PBP constant pointing to the &quot;Too Low &quot; string
  
 </i></b></font><b>TooRich</b>: <b>POKECODE </b><font color="#800000"><b>$FE</b></font>,<font color="#800000"><b>$C0</b></font>,<font color="#FF0000">&quot;TOO RICH&quot;</font>,<font color="#800000"><b>0
</b></font><b>_TooRich  </b><font color="#008000"><b>CON </b></font><b>EXT             </b><font color="#0000FF"><b><i>; PBP constant pointing to the &quot;Too Rich&quot; string
  
</i></b></font><b>FlashSize </b><font color="#008000"><b>CON </b></font><b>EXT
</b><font color="#008000"><b>ASM
   </b></font><font color="#000080">ifdef BSR
FlashSize = 2                 </font><font color="#0000FF"><b><i>; 18F has byte addressing (2)
   </i></b></font><font color="#000080">else
FlashSize = 1                 </font><font color="#0000FF"><b><i>; 12F/16F has words (1)
   </i></b></font><font color="#000080">endif
</font><font color="#008000"><b>ENDASM

</b></font><b>MidChar   </b><font color="#008000"><b>CON </b></font><b>EXT             </b><font color="#0000FF"><b><i>; MidChar is the border between
</i></b></font><font color="#000080">@MidChar = 8 * FlashSize      </font><font color="#0000FF"><b><i>; 8 char segments of the 1x16 LCD being used

</i></b></font><b>CountLength  </b><font color="#008000"><b>CON </b></font><b>EXT
</b><font color="#000080">@CountLength = 15 * FlashSize

</font><font color="#0000FF"><b><i>;=============================================================================
</i></b></font><b>Main</b>:
    <font color="#008000"><b>DEBUGIN </b></font>[<b>Uin</b>]             <font color="#0000FF"><b><i>; Serial Input
    </i></b></font><font color="#008000"><b>LCDOUT </b></font><font color="#800000"><b>$FE</b></font>, <font color="#800000"><b>2             </b></font><font color="#0000FF"><b><i>; LCD Home Cursor

    </i></b></font><font color="#008000"><b>FOR </b></font><b>BarCount </b>= <font color="#800000"><b>0 </b></font><font color="#008000"><b>TO </b></font><b>CountLength </b><font color="#008000"><b>STEP </b></font><b>FlashSize
        </b><font color="#008000"><b>IF </b></font>(<b>BarCount </b>= <b>MidChar</b>) <font color="#008000"><b>THEN LCDOUT </b></font><font color="#800000"><b>$FE</b></font>,<font color="#800000"><b>$C0  </b></font><font color="#0000FF"><b><i>; Second half of 1x8 LCD
        </i></b></font><b>PEEKCODE </b>(<b>_BarSteps</b>+<b>BarCount</b>),<b>BarValue       </b><font color="#0000FF"><b><i>; Get BarValue from Table
        </i></b></font><b>R0</b>.<b>LowByte </b>= <b>Uin </b>- <b>BarValue
        </b><font color="#008000"><b>IF </b></font><b>Carry </b><font color="#008000"><b>THEN                                </b></font><font color="#0000FF"><b><i>; Uin &gt; BarValue
            </i></b></font><font color="#008000"><b>LCDOUT </b></font><font color="#800000"><b>255                               </b></font><font color="#0000FF"><b><i>;  show a Full char
        </i></b></font><font color="#008000"><b>ELSE                                         </b></font><font color="#0000FF"><b><i>; Uin &lt;= BarValue
            </i></b></font><font color="#008000"><b>LCDOUT </b></font><font color="#FF0000">&quot; &quot;                               </font><font color="#0000FF"><b><i>;  show a blank
        </i></b></font><font color="#008000"><b>ENDIF
    NEXT </b></font><b>BarCount
    
    R0</b>.<b>LowByte </b>= <b>Uin </b>- <font color="#800000"><b>22                            </b></font><font color="#0000FF"><b><i>; if Uin &lt; 22
    </i></b></font><font color="#008000"><b>IF </b></font>!<b>Carry </b><font color="#008000"><b>THEN </b></font><b>MsgAddr </b>= <b>_TooLow </b>: <font color="#008000"><b>GOSUB </b></font><b>ShowMsg

    R0</b>.<b>LowByte </b>= <b>Uin </b>+ <font color="#800000"><b>29                           </b></font><font color="#0000FF"><b><i>; if Uin &gt; 227
    </i></b></font><font color="#008000"><b>IF </b></font><b>Carry </b><font color="#008000"><b>THEN </b></font><b>MsgAddr </b>= <b>_TooRich </b>: <font color="#008000"><b>GOSUB </b></font><b>ShowMsg
</b><font color="#008000"><b>GOTO </b></font><b>Main

</b><font color="#0000FF"><b><i>;=============================================================================
</i></b></font><b>ShowMsg</b>:
    <b>PEEKCODE MsgAddr</b>, <b>B0
    </b><font color="#008000"><b>IF </b></font><b>B0 </b>= <font color="#800000"><b>0 </b></font><font color="#008000"><b>THEN RETURN
    LCDOUT </b></font><b>B0
    MsgAddr </b>= <b>MsgAddr </b>+ <b>FlashSize
    </b><font color="#008000"><b>GOTO </b></font><b>ShowMsg
</b><font color="#008000"><b>RETURN
</b></font>