ultra - BASIC Commands

Name:

ultra

Syntax:

ULTRA pin, variable

ULTRA pin, pin, variable

Pin - is a variable/constant which specifies the i/o pin to use.

Variable - receives the result (0; no object detected, 1-255 distance in centimetres).

Description:

The 'ultra' command calculates the distance to an obstacle using the SRF005 ultrasonic range finder (distance sensor).

The SRF005 module should be wired for "mode 2" operation (with pin 4 to 0V) so that it uses a single pin for both trigger and echo. This is described in the SRF005 datasheet. If you wish to use 'single pin mode' instead specify two pins (trigger, echo) in the command.

The 'pin' specified in the 'ultra' command for single pin mode must be a bi-directional pin (capable of both input and output) and is used to trigger the ultrasound sensor and read the sensor echo pulse.

The 'ultra' command initiates a triggering of the SRF005 ultrasound sensor connected to the specified pin, then the returned echo pulse is measured and converted to a byte value which is placed in the 'variable' as a 1 to 255 distance in centimetres. A value of zero indicates no object was detected within range. Any object detected over 255 cm away (e.g. at 3m) will also return a value of 255.

Effect of Increased Clock Speed

This command will only function correctly at the default 4MHz (8MHz on X2 parts).

Equivalent commands

An 'ultra pin, variable' command on a PICAXE M2 is equivalent to -

    pulsout pin, 2
    pulsin pin, 1, wordvariable
    variable = wordvariable max 1479 * 10 / 58

An 'ultra pin, variable' command on a PICAXE X2 is equivalent to -

    pulsout pin, 2
    pulsin pin, 1, wordvariable
    variable = wordvariable max 2958 * 5 / 58

'Inch' equivalent

There is no 'inch' version of the ultra command within the PICAXE language, but inch calculation could be programmed by the user as follows:

Inch version equivalent on PICAXE M2 -

    pulsout pin, 2
    pulsin pin, 1, wordvariable
    variable = wordvariable max 3774 * 10 / 148

Inch version equivalent on PICAXE X2 -

    pulsout pin, 2
    pulsin pin, 1, wordvariable
    variable = wordvariable max 7548 * 5 / 148

Applies To:

All M2 and X2 parts

See Also:

Related Create:

Ultrasonic (SRF005)

ultra example

Light an LED if there is an obstacle less than 10cm away.

Code Example:

main:
   ultra C.1, b1   ; measure the distance
   if b1 > 0 and b1 < 10 then
      high B.2      ; LED on
   else
      low B.2      ; LED off
   end if
   pause 200 	   ; wait 200 ms 
   goto main

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