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Path to Programmable
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Path to Programmable
Blog Path to Programmable - Blog 11 - Video Project Gimbal
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  • Author Author: rsc
  • Date Created: 13 Jan 2019 1:31 AM Date Created
  • Views 170 views
  • Likes 10 likes
  • Comments 3 comments
  • path to programmable
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Path to Programmable - Blog 11 - Video Project Gimbal

rsc
rsc
13 Jan 2019

To control my camera module, I'm going to use a X-Y gimbal made from RC servos.

I will run the servos from the MiniZed.

To do this, I have modified the code from the IP training to run two RC servos instead (and addition to) the PL leds.

The new Vivado Block Design is as follows:

I added another instance of the IP PWM_w_Int, and connected it to PL_LED_G

The new address of the second PWM channel (Green LED) is 0x40002000:

The green and red PL LED pins are also available on the Arduino headers as A3 and A4 so I didn't have to add any new port definitions:

The Implementation schematic is shown below.

I stumbled upon the IO Bank definitions after getting many bitstream generation errors and set up the Green LED PWM2 on E13:

It turns out that theHW lab example code PWM period is set to 20ms, which is what RC servos use, so that didn't need to be changed.

The test code for setting a PWM pulse from 1ms (50,000 clock cycles) to 2ms (100,000 clock cycles) was changed to the following:

brightnessRed = (period * 5000)+50000;

brightnessGreed = (period * 5000)+50000;

#define PWM_BASE_ADDRESS               0x43C00000

#define PWM_BASE_ADDRESS2              0x40002000

Xil_Out32(PWM_BASE_ADDRESS, brightnessRed);

Xil_Out32(PWM_BASE_ADDRESS2, brightnessGreen);

A period value of 0 is now approx. -45deg servo travel (1000us pulse), and a period value of 10 is approx. +45deg servo travel (2000us pulse).

Here's my servo test setup:

Here's a scope trace of the PWM signal:

I may have to boost the PWM signal from 3.2V to 5VDC for the servos to operate consistently.

Currently the video streamer and the servo drivers are on two separate MiniZed boards, although I am trying to get everything to work together on one board.

**update 19 Jan

I added a level shifter to the AO3 and AO4 outputs and ran a short test program that runs the servos in sine wave patterns:

    for (i = 1; i < 3610; i++){

     Xil_Out32(PWM_BASE_ADDRESS,75000+(25000*sin(i*3.14/1800)));

     Xil_Out32(PWM_BASE_ADDRESS2,75000+(25000*sin(i*3.14/900)));

         for (i2 = 1; i2 < 40000; i2++){

         }

    }

   

Here's a video of the gimbal operating.

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Top Comments

  • rsc
    rsc over 3 years ago in reply to genebren +1

    Hi Gene,

    I have a 9-axis IMU the MPU9250 with I2C interface I've been using with the RPi I will try and implement in this project eventually.

    Scott

  • aspork42
    aspork42 over 3 years ago +1

    Nice job! Do you know why the issues with E13 versus using E12?

    You could also use the accelerometer right on board the MiniZed if you're able to read it. I wasn't able to find any example code for I2C…

  • aspork42
    aspork42 over 3 years ago

    Nice job! Do you know why the issues with E13 versus using E12?

    You could also use the accelerometer right on board the MiniZed if you're able to read it. I wasn't able to find any example code for I2C that worked; which is the bus that the sensor is on.

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  • rsc
    rsc over 3 years ago in reply to genebren

    Hi Gene,

    I have a 9-axis IMU the MPU9250 with I2C interface I've been using with the RPi I will try and implement in this project eventually.

    Scott

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  • genebren
    genebren over 3 years ago

    Nice project.  It will be interesting to see how this all works out for you.  Are you going to be detecting the pitch and roll to drive the gimbal from sensors, or getting this information from some other equipment?

     

    Keep up the good work!

    Gene

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