Cannot get PWM 33 to work.
Has anyone worked with MRAA on UP2 (Python) PWM pins are suppose to be 33,32,16. I have three MG996R servos connected, I can move the servos on pins 32 and 16, but 33 seems to be unresponsive. These are powered off the 5v (No external) but it makes no difference when removing one or both of the other servos so I don't think it is power issue.
Advice would be awesome, stuck on releasing some code due to this
Ugh, cannot edit post. mraa-gpio list:
03 I2C_SDA: GPIO I2C 05 I2C_SCL: GPIO I2C 07 GPIO4: GPIO 08 UART_TX: GPIO UART 10 UART_RX: GPIO UART 11 UART_RTS: GPIO UART 12 I2S_CLK: GPIO 13 GPIO27: GPIO 15 GPIO22: GPIO 16 PWM3: GPIO PWM 18 GPIO24: GPIO 19 SPI0_MOSI: GPIO SPI 21 SPI0_MISO: GPIO SPI 22 GPIO25: GPIO 23 SPI0_CLK: GPIO SPI 24 SPI0_CS0: GPIO SPI 26 SPI0_CS1: GPIO SPI 27 ID_SD: GPIO I2C 28 ID_SC: GPIO I2C 29 GPIO5: GPIO 31 GPIO6: GPIO 32 PWM0: GPIO PWM 33 PWM1: GPIO PWM 35 I2S_FRM: GPIO 36 UART_CTS: GPIO UART 37 GPIO26: GPIO 38 I2S_DIN: GPIO 40 I2S_DOUT: GPIO
I think you have already tried to use only PWM on pin 33 without the others. Do you confirm that this approach doesn't work?
In general, powering 3 servos from the mainboard is not a good idea. I would suggest to use an external power source.
Thank you for the reply, yes it makes no difference if I have 1 or 3 servos attached. We may be able to add an additional power supply but it changes our design and not really something we want to do at this stage.
Regarding your design, you should consider that the pins are connected to a MAX10 FPGA.
As the pins are TTL, they are not supposed to be used to drive servos directly, but they can at most power an LED.
They have a maximum output current per pin of 25mA and voltage level of 3.3V.
If the servos you are using exceed those values, it is not fine, you may have damaged the FPGA and experience unexpected behavior or non-working pins.
Thanks for the info we are using https://www.electronicoscaldas.com/datasheet/MG996R_Tower-Pro.pdf we are very far into this project, what would your suggestions be? The entire project is based around UP2 boards, published code is working fine with the hardware with exception to this pin. We needed 6 servos really but settled for 3, with only 2 working.
There is another question I would like to ask, we are using OpenVINO and NCS2 for depth measurements for the robot, this requires non root execution of the program (Long story), I have managed to get udev rule set up for GPIO allowing non root control, what rules would work for PWM?
What I have tried so far:
# /etc/udev/rules.d/80-gpio-noroot.rules # Corrects sys GPIO permissions so non-root users in the gpio group can manipulate bits # Change group to gpio SUBSYSTEM=="gpio", PROGRAM="/bin/sh -c '/bin/chown -R root:gpio /sys/devices/soc.0/*pinctrl/gpio'" # Change user permissions to ensure user and group have read/write permissions SUBSYSTEM=="gpio", PROGRAM="/bin/sh -c '/bin/chmod -R ug+rw /sys/devices/soc.0/*pinctrl/gpio'" SUBSYSTEM=="pwm*", PROGRAM="/bin/sh -c '\ chown -R root:gpio /sys/class/pwm && chmod -R 770 /sys/class/pwm;\ chown -R root:gpio /sys/bus/pci/devices/0000\:00\:19.*/pxa2xx-spi.*/spi_master/spi1/spi1.0/pwm/pwmchip0 && chmod -R 770 /sys/bus/pci/devices/0000\:00\:19.*/pxa2xx-spi.*/spi_master/spi1/spi1.0/pwm/pwmchip0\ '"
chown -R root:gpio /sys/class/gpio chmod -R ug+rw /sys/class/gpio chown -R root:gpio /sys/class/pwm chmod -R ug+rw /sys/class/pwm
I resolved the issue above with non-root GPIO, the rule was:
SUBSYSTEM=="pwm*", PROGRAM="/bin/sh -c '\ chown -R root:gpio /sys/class/pwm && chmod -R 770 /sys/class/pwm;\ chown -R root:gpio /sys/devices/pci0000:00/0000:00:1a.0/pwm/pwmchip* && chmod -R 770 /sys/devices/pci0000:00/0000:00:1a.0/pwm/pwmchip*;\ '"
Issue still remains with the PWM pin. I will try with another powersupply for the servos, but still it does not work on it's own.
I moved to another device as even with the rules above still had permission errors. On this device all pins are working. I will debug when I get some time and try and see what the issue was. Will take into account your suggestions about the external power. With external power do you see any other issues. This robot is our prototype of a larger robot, it is not meant for heavy lifting etc, just to show how it is controlled by our open source network.
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