Problem with servos in export to arduino

[jenncross]

This was with CLVP 1.4.383 on Windows 7

I had a set of expressions and sequences that I made originally with a blue hummingbird. I opened them with same robot upgraded with a hummingbird duo and the sequences all seemed to function just fine running from CLVP. However when I exported the sequence to arduino many of the servo values were incorrect.

The "Dino - Chill.xml"

"<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE expression PUBLIC "-//CREATE Lab//TeRK//Expression//EN" "http://www.createlab.ri.cmu.edu/dtd/terk/expression.dtd">
<expression version="1.0">
   <services>
      <service type-id="::TeRK::motor::VelocityControllableMotorService">
         <operation name="setVelocity">
            <device id="0">
               <parameter name="velocity"><![CDATA[204]]></parameter>
            </device>
         </operation>
      </service>
      <service type-id="::TeRK::servo::SimpleServoService">
         <operation name="setPosition">
            <device id="3">
               <parameter name="position"><![CDATA[219]]></parameter>
            </device>
            <device id="1">
               <parameter name="position"><![CDATA[219]]></parameter>
            </device>
            <device id="0">
               <parameter name="position"><![CDATA[90]]></parameter>
            </device>
         </operation>
      </service>
      <service type-id="::TeRK::led::FullColorLEDService">
         <operation name="setColor">
            <device id="0">
               <parameter name="red"><![CDATA[0]]></parameter>
               <parameter name="green"><![CDATA[0]]></parameter>
               <parameter name="blue"><![CDATA[255]]></parameter>
            </device>
            <device id="1">
               <parameter name="red"><![CDATA[0]]></parameter>
               <parameter name="green"><![CDATA[0]]></parameter>
               <parameter name="blue"><![CDATA[255]]></parameter>
            </device>
         </operation>
      </service>
   </services>
</expression>

became

void DinoChill(){
    hummingbird.setMotor(1,-204);
    hummingbird.setServo(4,-219);
    hummingbird.setServo(2,-219);
    hummingbird.setServo(1,-90);
    hummingbird.setTriColorLED(1,0,0,255);
    hummingbird.setTriColorLED(2,0,0,255);
}

The first issue is that the values sent to the servo became negative when in the XML the value was positive. The second issue is that the current setServo function takes the servo position as 0-180 degrees (not the 0-255 value stored in the xml expression), so that conversion was omitted.

Another example, "Dino - Mouth Open"

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE expression PUBLIC "-//CREATE Lab//TeRK//Expression//EN" "http://www.createlab.ri.cmu.edu/dtd/terk/expression.dtd">
<expression version="1.0">
   <services>
      <service type-id="::TeRK::servo::SimpleServoService">
         <operation name="setPosition">
            <device id="1">
               <parameter name="position"><![CDATA[173]]></parameter>
            </device>
            <device id="3">
               <parameter name="position"><![CDATA[173]]></parameter>
            </device>
         </operation>
      </service>
   </services>
</expression>

became

void DinoMouthOpen(){
    hummingbird.setServo(2,173);
    hummingbird.setServo(4,173);
}

which suffered from not being converted to the 0-180 range, but was oddly not made negative?

[chrisbartley]

A little more info...

In Expression_CodeGenerator.java, there's no scaling done of the values. That is, the values that the VP stores in the expression XML are the values in the range that the Hummingbird USB HID API expects. But, for the VP user interface, we scale the values to [0, 180] to make things easier to understand for the user. The Arduino code generator is simply taking the values in the XML and using them, unscaled, in the generated code. My understanding is that the Hummingbird library for Arduino is expecting servo values in the range [0,180]. I can only guess that the Arduino code conversion either just was not well tested for servos, or perhaps the Hummingbird library for Arduino has changed since the Arduino export was written. Either way, it sounds like Expression_CodeGenerator needs to start scaling the servo values to [0,180]. It's worth checking whether motor values need to be scaled as well.

As for the motors always getting a negative value, this is definitely due to the logic in Expression_CodeGenerator. For some reason, there's an else condition which negates the motor value. I have no idea why it's being negated.

Finally, as for the servo values sometimes getting a negative value, this appears to be due to a motor flag getting set to true, but never getting reset to false for things that aren't motors.

This has been addressed in the BirdBrainDev branch