PBP projects for R/C models

[Kenjones1935]

I would like to read a TIMER immediately after sending a trigger pulse to my SONARS. Then immediately reset it for the next cycle. (Which TIMER am I not using with PAUSE or HPWM.) Anybody?

I want to calculate velocity. I plan to subtract two SONAR distance readings and divide by the time elapse between triggers. Units of distance sound travels in a millisecond (13.2 inches) divided by the number of milliseconds. (Could do no translation: Use the distance sound travels in a 4Mhz tick divided by the number of those ticks between SONAR triggers.) Could I explain that to middle school students?

I have not been translating SONAR echo pulses to inches. Instead I learned how to translate inches into SONAR echo times. That is how I set up my distance parameters. At 1100 feet per second that is 13.2 inches per millisecond. (When measuring distance the PIC must divide by two. It is measuring time for an echo response.)

Any simple code snippets you know of?

Ken

[Kenjones1935]

I would like to use the 4 Meg counter to measure time in seconds and the SONAR responses to measure distance in inches.

I could then set up CONstants that would be recognizable
and measurable by middle school students with a yardstick and a watch with a second hand.

How?

Ken

[mackrackit]

This displays the sonar distance in inches. Using the "ping" module from Parallex.

'  18F6680
    DEFINE OSC 20
    @ __CONFIG    _CONFIG1H, _OSC_HS_1H
    @ __CONFIG    _CONFIG2H, _WDT_OFF_2H & _WDTPS_128_2H
    @ __CONFIG    _CONFIG4L, _LVP_OFF_4L
    INCLUDE "modedefs.bas"
    DEFINE LCD_DREG     PORTG
    define LCD_DBIT     0
    DEFINE LCD_RSREG    PORTE
    DEFINE LCD_RSBIT    0
    DEFINE LCD_EREG     PORTE
    DEFINE LCD_EBIT     1
    DEFINE LCD_BITS     4
    DEFINE LCD_LINES    4
    DEFINE LCD_COMMANDUS    3000
    DEFINE LCD_DATAUS   150
    PAUSE 500
    PAUSE 1000
    
    INCONSTANT  CON 890
    INDISTANCE  VAR WORD
    TIME        VAR WORD
    
    START:
    HIGH PORTB.3
    PULSOUT PORTB.3,2
    PULSIN  PORTB.3,1,TIME
    INDISTANCE = INCONSTANT ** TIME
    LCDOUT $FE,1,DEC3 INDISTANCE," INCHES" 
    PAUSE 100
    GOTO START

[Kenjones1935]

My robocars have no LEDs. They have no debugger and no break points. Using PICkit 2 I can read EEPROM. My code can write in that area using the WRITE command.

When I have my car on blocks connected via the PICkit2 USB cable, I would like to do a READ and see in the EEPROM section some words that the code placed there while it ran represented as decimal numbers.

hex includes the digits 0-9. Is there a library routine or a command to which I can give a WORD containing a positive hexadecimal number (for example the response from a SONAR) and it will return that number in decimal format represented with the digits 0-9 in least significant (as read by PICkit2) to the right?

Ken

[ScaleRobotics]

Yes, but how are you checking to see that hpwm is not working, sometimes. Are you really observing the signal itself, or just the reaction it is "supposed" to cause? You have the tools to look at the source .... why not use them?

[Kenjones1935]

I compile the code with the WHILE command. During the first three seconds after powering up the wheels steer and roll as expected. I then comment out the WHILE, recompile and program. For the first three seconds the car does nothing. The PAUSEs work but the HWPM commands do not.

After the initial three seconds both programs work identically.

Ken

[ScaleRobotics]

The PAUSEs work but the HWPM commands do not.

You really need to test the signal Ken. Without observing the signals, you really can't say HPWM doesn't work. How about getting your Pickit2 out and using the logic probe again?

[Kenjones1935]

Scalerobotics:

I used the oscilloscope you gave me way back when. You are correct. The PWM signals appear to be there from the get go, but the wheels neither rotated nor steered until the program counter got past 'main:'.

The pulse traces on the scope are stable and easily readable.

All my fault - nothing new there - just between us programmers. I thought I had set PORTC.0 low with a TRISC = %11110000 when in fact I had set it to be an output. This is the pin that drives the DPDT switch that selects between PIC control and radio receiver control. Once I activated the LOW portc.0 located just before the HPWM commands. Lo and behold!

Thank you for your patience and smarts.

Ken

[Kenjones1935]

One of you knowledgeable people please come to my aid.

I am studying the .ASM code which my PBP produces. My Microchip 16F887 Data Document DS41291F page 232 lists the Assembly Language commands for the 16F88x chips. There is no HPWM in that list. Yet my .asm code contains:

HPWM?CCC 001h, _Right, 032h

How does the Assembler know what to do with that string?

I figured it must be in one of the includes. I searched all the files in the PBP directory, the Mecanique directory and the Microchip directory for the string HPWM. No luck except in my .pbp code that I wrote and its resulting .asm.

This is not a show stopper, but I would like to know what I am missing.

On the very good news side, MIT's Lincoln Laboratory has an Educational Outreach initiative. They have picked up the idea of racing robocars. I am sure that they will take this to the next level - whatever that is.
Ken