Taxi Meter Help MPASM

hello there,

i was hoping you could help me with my project on a taxi meter where:

• The motor start/stop switch increases the mileage

• Detects the temperature of the sensor

• When the button is pressed it displays the fare/distance respectively.( where the fare starts at £5)

i have included pictures and also the code where i have managed to display the distance and temperature but not increment the actions that are being made.

the only problem im having is that im not sure how to make the motor increment a counter just after the distance: and same with the temperature, as i have done both these commands seperately on a 7 segment i just cant get my head round how to get it onto the LCD display...
thank you

Code (Text):

1. ;http://digitaldiy.io/articles/mcu-programming/assembly/55-assembly-example/114-mpasm-tutorial-liquid-crystal-display-lcd#.WKDWRDvyiUk
2. ;====================================================================
3. ; Main.asm file generated by New Project wizard
4. ;
5. ; Created:   Sun Feb 12 2017
6. ; Processor: PIC16F877
7. ; Compiler:  MPASM (Proteus)
8. ;====================================================================
9.  
10.  
11. #include p16f877a.inc             ; Include register definition file
12.  
13. __config 0x3D18 ;sets the configuration settings (osc type etc.)
14. ;====================================================================
15. ; VARIABLES
16. ;====================================================================
17. LCD_PORT Equ PORTB
18. LCD_TRIS Equ TRISB
19. LCD_RS Equ 0x02 ;LCD handshake lines
20. LCD_E Equ 0x03
21.  
22. CBLOCK 0x20
23.   count ; Counter used when switch pressed has stopped
24.   count1 ; 160us Counter variable
25.   counta ; variables for delay timers
26.   countb ; variables for delay timers
27.   LCDTemp ; 4 bit for LCD
28. ENDC ;
29.  
30. ;====================================================================
31. ; RESET and INTERRUPT VECTORS
32. ;====================================================================
33.  
34. ; Reset Vector
35. RST   code  0x00
36.   goto  Start
37.  
38. Text
39. addwf PCL, f
40. retlw 'D'
41. retlw 'i'
42. retlw 's'
43. retlw 't'
44. retlw 'a'
45. retlw 'n'
46. retlw 'c'
47. retlw 'e'
48. retlw ':'
49. retlw 'M'  
50. retlw 'i'
51. retlw 'l'
52. retlw 'e'
53. retlw 's'
54. retlw 0x00
55.  
56. Text2
57. addwf PCL, f
58. retlw 'T'
59. retlw 'e'
60. retlw 'm'
61. retlw 'p'
62. retlw 'e'
63. retlw 'r'
64. retlw 'a'
65. retlw 't'
66. retlw 'u'
67. retlw 'r'
68. retlw 'e'
69. retlw ':'
70. retlw b'00110000'   ;0.
71. retlw 0x00    
72.  
73. DispNumNoDot
74. addwf PCL, f
75. retlw b'00110000'   ;0.
76. retlw b'00110001'   ;1.
77. retlw b'00110010'   ;2.
78. retlw b'00110011'   ;3.
79. retlw b'00110100'   ;4.
80. retlw b'00110101'   ;5.
81. retlw b'00110110'   ;6.
82. retlw b'00110111'   ;7.
83. retlw b'00111000'   ;8.
84. retlw b'00111001'   ;9.    
85. ;====================================================================
86. ; CODE SEGMENT
87. ;====================================================================
88.  
89. PGM   code
90.       GOTO     Start
91. Start
92.  
93. bsf STATUS, RP0 ; select bank 1
94. clrf PORTA ; Initialize PORTA by setting output data latches
95. movlw b'00000000' ; PortA Outputs
96. movwf TRISA ; All portA pins are inputs
97. movlw b'00000000' ; PortB Outputs
98. movwf TRISB ; Change PortB I/O
99. bcf STATUS, RP0 ; select bank 0
100.  
101. call LCDInit ; Initialize the LCD Display
102.  
103. ; Main program...
104.  
105. clrf count
106. Message
107.  
108. movf count, w ; put counter value in W
109. call Text ; get a character from the text table
110. xorlw 0x00 ; is it a zero?
111. btfsc STATUS, Z
112. goto NextMessage ; display next message if finished
113. call LCD_Char
114. incf count, f
115. goto Message
116.  
117. NextMessage
118. call LCD_L2 ;move to 2nd row, first column
119. clrf count ;set counter register to zero
120.  
121. Message2
122. movf count, w ;put counter value in W
123. call Text2 ;get a character from the text table
124. xorlw 0x00 ;is it a zero?
125. btfsc STATUS, Z
126. goto EndMessage
127. call LCD_Char
128. incf count, f
129. goto Message2
130.  
131. EndMessage
132.  
133. ; Infinate loop
134. Stop
135. goto Stop ;endless loop
136.  
137. ; LCD routines and subs
138. LCDInit ; 4 Bit Initialization...
139. bcf LCD_PORT, LCD_RS ;
140. movlw 0x030 ; Send the Reset Instruction
141. movwf LCD_PORT ;
142. call Pulse_e ; Pulse LCD_E
143. call Del05 ; Delay 5ms
144.  
145. movlw 0x020 ; Send the Data Length Specification
146. movwf LCD_PORT ;
147. call Pulse_e ; Pulse LCD_E
148. call D160us ; Delay of 160us
149. movlw 0x028 ; Set Interface Length
150. call LCDIns ;
151. movlw 0x010 ; Turn Off Display
152. call LCDIns ;
153. movlw 0x001 ; Clear Display RAM
154. call LCDIns ;
155. movlw 0x006 ; Set Cursor Movement
156. call LCDIns ;
157. movlw 0x00C ; Turn on Display/Cursor
158. call LCDIns ;
159. call LCD_Clr ; Clear the LCD
160. return ;
161.  
162. LCDIns ; Send the Instruction to the LCD
163. movwf LCDTemp ; Save the Value
164. andlw 0xF0 ; Most Significant Nibble first
165. movwf LCD_PORT ;
166. bcf LCD_PORT, LCD_RS ;
167. call Pulse_e ;
168. swapf LCDTemp, w ; Least Significant Nibble Second
169. andlw 0xF0 ;
170. movwf LCD_PORT ;
171. bcf LCD_PORT, LCD_RS ;
172. call Pulse_e ;
173. call Del05
174.  
175. return ;
176.  
177. ;LCD_CharD
178.  
179. LCD_Char ; Send the Character to the LCD
180. movwf LCDTemp ; Save the Value
181. andlw 0xF0 ; Most Significant Nibble first
182. movwf LCD_PORT ;
183. bsf LCD_PORT, LCD_RS ;
184. call Pulse_e ;
185. swapf LCDTemp, w ; Least Significant Nibble Second
186. andlw 0xF0 ;
187. movwf LCD_PORT ;
188. bsf LCD_PORT, LCD_RS ;
189. call Pulse_e ;
190. call Del05 ;
191. nop ;
192. return ;
193.  
194.  
195.  
196. LCD_L2: movlw 0xc0 ; move to 2nd row, first column
197. call LCDIns ;
198. return
199.  
200.  
201. LCD_Clr movlw 0x01 ; Clear display
202. call LCDIns ;
203. return
204.  
205.  
206. Pulse_e ;
207. bsf LCD_PORT, LCD_E ; LCD Enable pulse to write data from PORTB
208. bcf LCD_PORT, LCD_E ;
209. nop ;
210. return ;
211.  
212.  
213. ; Delay routines...
214. D160us
215. clrf count1 ;
216. bsf count1, 5 ; Delay 160 usecs
217. bsf count1, 3 ;
218. decfsz count1, f ;
219. goto $ - 1 ;
220. return ;
221.  
222.  
223. Del05 movlw 0x05 ; delay 5.000 ms (1 MHz clock)
224. goto d0 ;
225. d0 movwf count1 ;
226. d1 movlw 0xC8 ; x200  delay 1mS
227. movwf counta ;
228. movlw 0x05 ;   x5
229. movwf countb ;
230. Del_0 decfsz counta,f ;
231. goto $+2 ;
232. decfsz countb,f ;
233. goto Del_0 ;
234. decfsz count1,f ;
235. goto d1 ;
236. return
237.  
238.  
239. ;====================================================================
240.   END

 

I don't see where you try to print data after your message. Take this part of the code:

Code (ASM):

1.  
2. Text
3.      addwf PCL, f
4.      retlw 'D'
5.      retlw 'i'
6.      retlw 's'
7.      retlw 't'
8.      retlw 'a'
9.      retlw 'n'
10.      retlw 'c'
11.      retlw 'e'
12.      retlw ':'
13.      retlw 'M'
14.      retlw 'i'
15.      retlw 'l'
16.      retlw 'e'
17.      retlw 's'
18.      retlw 0x00
19.      clrf  count
20. Message
21.      movf count, w            ; put counter value in W
22.      call Text                ; get a character from the text table
23.      xorlw 0x00               ; is it a zero?
24.      btfsc STATUS, Z
25.      goto NextMessage         ; display next message if finished
26.      call LCD_Char
27.      incf count, f
28.      goto Message
29.  

That simply prints your messages in order. You need to return after printing "Distance" to insert your data, then add "Miles." I suspect you see that using 'retlw' prevents you from inserting a variable. When I need to add a variable following a printed label, I do not do it the way you are trying to do it, but as this is homework, here is something to try using your code's structure:

Code (ASM):

1.  
2. Start  
3.      movlw     '1'       ;example odometer data
4.      movwf     Tens
5.      movlw     '6'       ;example odometer data
6.      movwf     Ones
7.      goto       Message
8. Text
9.      addwf PCL, f
10.      retlw 'D'
11.      retlw 'i'
12.      retlw 's'
13.      retlw 't'
14.      retlw 'a'
15.      retlw 'n'
16.      retlw 'c'
17.      retlw 'e'
18.      retlw ':'
19.      retlw 0xFF
20.      retlw 'M'
21.      retlw 'i'
22.      retlw 'l'
23.      retlw 'e'
24.      retlw 's'
25.      retlw 0x00
26. ;====================================================================
27. ; CODE SEGMENT
28. ;====================================================================
29.      clrf      count  
30. Message
31.      movf      count, w       ; put counter value in W
32.      call      Text           ; get a character from the text table
33.      xorlw     0xFF           ; is it a zero?
34.      btfsc     STATUS,2
35.      call      PutMiles
36.      xorlw     0x00
37.      btfsc     STATUS,2
38.      goto      NextMessage
39.      call      LCD_Char
40.      incf      count,f
41.      goto      Message
42. PutMiles
43.      movf      Tens,w
44.      call      LCD_Char
45.      movf      Ones,w
46.      call      LCD_Char
47.      movlw     0x20           ;ascii "space" between data and unit
48.      return
49. LCD_Char
50. ;     <insert your code here>
51. NextMessage
52.      end
53.  

That code has not been tested. Obviously, you need to get the odometer mileage, convert to BCD, and then convert the decimal digits to ascii.

John

EDIT: On thinking a little further about your question, let me emphasize that the approach I showed was based entirely on trying to fit a variable into your already fixed print routine, or what appeared fixed to me. Here are some suggestions for change based on what I do.
1) Remember that LCD's do not need to be refreshed. So, if you print something like "Distance:" followed by some value, followed by a unit, "Miles," the only thing you need to print with each change is the value.
2) You can get to the value by coordinates, e.g, line 0, 10 will get you one space after the colon for Distance: .
3) If the "value" is always the same format, say 2 digits, re-writing at the same location simply writes over what is there.
4) Based on the above, I suggest you break your write routines into smaller chunks and/or write spaces (0x20) there the values go. Then as you determine each value, write it to a specific location.
5) Your compiler may support some shorthand. While there is nothing wrong with what you wrote using retlw's, I usually write something like dt "Distance: " (I use MPLab 8.92.) That is easier to read and takes less space on paper (program memory is the same). If disassembled, it will show exactly as yours, i.e., a series of retlw instructions for each character. Be sure to use double quote (") instead of single quote (') when you want more than one character.
6) Make one print routine and use that. I call mine "Put232" ; although, it has very little to do with that interface today. Each character is moved into W register, then that routine is called. Exactly the same routine is used for placing the cursor in the correct spot as is used for printing a character.
7) I use 1/4" squared graph paper to plot out my print routines, That way, I can be sure what will overwrite and what needs to be cleared.