Nuts & Volts - March 2006

cost you around $5 for the parts, depending on what you have in your junk box. As far as assembly goes, I soldered the 78L05, diode, and resistor directly to the connector.

Software

then print the received value, as well as the Rot value.

Note that you have to access the ComInput command to pull the data out of the buffer or the ComBuff command will just keep getting larger and won’t ever return a 0.

Laps

First, Second, Third, and
Fourth.
Completed laps.

A call to initBike is also made. Notice that I am using com port 4. You will need to pass the com port number your interface is connected to.

Now, for the fun part. We will use a development program called Zeus. There is even a special free Nuts & Volts version up on the Nuts & Volts website ( www.nutsvolts.com). Let’s see how this will work.

Sensor Test

I’m going to start with a simple program just to test if the sensor is working properly.

Program 1 is fairly straightforward. We open up the com port. If the ComOpen returns a 0, we have an error so we display an error message and exit the program.

Once we have an open port, we raise DTR with the ComDTR command. This provides power to the interface.

We then run a very tight loop that checks the status of the com buffer with the ComBuff command. If it returns anything greater than 0, we know we have a sensor event.

We increment the Rot variable

Race Program 1

I’m not going to list the Race Program 1 here because it can be found on the Nuts & Volts website, as well as the Kronos Robotics website. I will, however, walk you through each section of the code.

There are four functions used to make up Race Program 1.

Main Loop

Here we set a variable called ticks. This variable will increment every 10 milliseconds. Once we get a tick value greater than 3, we reset the counter and using a random number generator, increment the position of each of the bot pips. For instance, take the following snipit of code:

• initBike(ComPort)

This function opens the indicated port and sets DTR to power the interface.

if Random(1, 10) > 4 then rots(2) = rots(2) + 1

endif

• Draw Track()

This function draws the track. You can change the FormBrush values to change the track colors.

• PlotPlayers(Player,

Rotations)

This function plots a player pip at a particular position on the track based on its Rotation value. Note that player 1 is the sensor and players 2-4

are the bot players.

Program 1. Sensor Test

‘Exercise Bike Sensor Test
func main()

gconst chBike 1
dim Rot as integer
clearall

if ComOpen(chBike,baud=9600,port = 4) = 0 then
  MsgBox(“Error Opening Com Port”)
  end
  endif

‘Power up the connector
ComDTR chBike,1

Loop:
  if ComBuff(chBike) > 0 then
     Rot = Rot + 1
     Print val(ComInput(chBike)),”Count=”+Rot
  endif

DoEvents
goto Loop

endfunc

• Main()

This is the entry point of the program. This is where most of the work gets done and, due to its complexity, it is broken down into its own sub sections.

Here, a random number between 1 and 10 is generated. If it is greater than 4, we will increment the bots rotation count. This equates to a 40% chance of this particular pip advancing one position every 40 ms.

By changing the value from 4 to 8, you effectively double the skill level of this bot. This would give the appearance of that bot running faster on average.