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by joan
Mon Jan 20, 2020 9:27 am
Forum: Troubleshooting
Topic: i2c detect -y 1 show all addresses.
Replies: 1
Views: 26

Re: i2c detect -y 1 show all addresses.

The Pi's GPIO should not be exposed to a voltage over 3V3. If they show 5V they are broken (or your meter is broken, or you are measuring between the wrong pins).
by joan
Mon Jan 20, 2020 8:35 am
Forum: Advanced users
Topic: phase opposite hardware pwm
Replies: 4
Views: 156

Re: phase opposite hardware pwm

pigpio uses hardware timed PWM.

Look at http://abyz.me.uk/rpi/pigpio/examples.h ... te_wave.py for a script to generate a pigpio program to generate waves.

The script uses an input file such as the following.

Code: Select all

# GPIO levels
23 11000001
11 01110000
12 00011100
 4 00000111
by joan
Sun Jan 19, 2020 10:15 pm
Forum: Troubleshooting
Topic: pigpio software PWM jitters when run together with raspivid
Replies: 11
Views: 219

Re: pigpio software PWM jitters when run together with raspivid

Thanks for the instructions. It might be a few days before I have a chance to try them out.
by joan
Sun Jan 19, 2020 8:17 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: current output on 5V header pins
Replies: 2
Views: 70

Re: current output on 5V header pins

Yes, provided there is enough spare from your power supply after feeding the Pi and any connected peripherals.

Which model Pi?
by joan
Sun Jan 19, 2020 4:19 pm
Forum: Troubleshooting
Topic: HMC5883L
Replies: 2
Views: 47

Re: HMC5883L

Go through the tutorial again taking particular care with the parts when you download and build the various libraries. Any problems?
by joan
Sun Jan 19, 2020 4:14 pm
Forum: Troubleshooting
Topic: PCA9685 servo board... how to use external power?
Replies: 3
Views: 38

Re: PCA9685 servo board... how to use external power?

The output pins are for control, not power. They will be 5V as that is what the PCA9685 chip generates. Perhaps 5V is not seen as a logic high to your 12V servos?
by joan
Sat Jan 18, 2020 8:50 pm
Forum: Troubleshooting
Topic: Struggling to connect DHT12
Replies: 1
Views: 33

Re: Struggling to connect DHT12

A clear photo of the connections you have made may help.

You could try it in non-I2C mode to see if that is more reliable.
by joan
Sat Jan 18, 2020 6:36 pm
Forum: Bare metal, Assembly language
Topic: i2c 2 alt functions
Replies: 11
Views: 216

Re: i2c 2 alt functions

That is when the GPIO are configured as INPUT. You are configuring them as ALT3.
by joan
Sat Jan 18, 2020 5:50 pm
Forum: Bare metal, Assembly language
Topic: i2c 2 alt functions
Replies: 11
Views: 216

Re: i2c 2 alt functions

As already said it does not appear to be routed to a Broadcom GPIO so there is no mode to set.

Have you tried the /dev/gpiochip interface? Alternatively talk directly to the I2C hardware as covered in the Broadcom specs.
by joan
Sat Jan 18, 2020 3:34 pm
Forum: Wolfram Language
Topic: Mathematica asks for an activation key and or password ...
Replies: 4
Views: 130

Re: Mathematica asks for an activation key and or password

What is reported by

uname -a

What is reported by

cat /etc/os-release
by joan
Sat Jan 18, 2020 11:42 am
Forum: Bare metal, Assembly language
Topic: i2c 2 alt functions
Replies: 11
Views: 216

Re: i2c 2 alt functions

It does not appear to be connected in the Pi4 either. The Pi4 omits SDA2 (it has SDA 0, 1, 3, 4, 5, 6).
by joan
Sat Jan 18, 2020 8:36 am
Forum: Bare metal, Assembly language
Topic: i2c 2 alt functions
Replies: 11
Views: 216

Re: i2c 2 alt functions

Perhaps no GPIO are connected to this bus? I have never heard of anything but I2C bus 0 and bus 1 hardware being used on the Pi.
by joan
Sat Jan 18, 2020 8:10 am
Forum: Troubleshooting
Topic: pigpio software PWM jitters when run together with raspivid
Replies: 11
Views: 219

Re: pigpio software PWM jitters when run together with raspivid

Tell me how to reproduce the fault and I will have a look.
by joan
Fri Jan 17, 2020 8:58 pm
Forum: General discussion
Topic: Raspberry motor controller
Replies: 3
Views: 121

Re: Raspberry motor controller

Actually the L298N only controls two DC motors at a time. For some reason they have put two motors on each output, but they will be both on/off at the same time. Most motor driver chips control two DC motors.
by joan
Fri Jan 17, 2020 11:50 am
Forum: Troubleshooting
Topic: Issue with running ESC Skywalker 30a
Replies: 1
Views: 44

Re: Issue with running ESC Skywalker 30a

Does the ESC work if you connect it in the place of a working ESC? If not then it sounds like the ESC is faulty.
by joan
Thu Jan 16, 2020 10:10 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: Maximum GPIO frequency from kernel space
Replies: 7
Views: 201

Re: Maximum GPIO frequency from kernel space

I mean you need to use one of the Pi's hardware peripherals to guarantee accurate and regular timing.

DMA as used in pigpio sampling will not work faster than perhaps 2 MHz.

I don't know anything about the DPI hardware or how SPI might be used to capture such data.
by joan
Thu Jan 16, 2020 6:03 pm
Forum: Troubleshooting
Topic: pigpio software PWM jitters when run together with raspivid
Replies: 11
Views: 219

Re: pigpio software PWM jitters when run together with raspivid

I don't know what is happening.

You can delete the pid file so you don't need to reboot.

sudo rm /var/run/pigpio.pid
by joan
Thu Jan 16, 2020 8:35 am
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: Maximum GPIO frequency from kernel space
Replies: 7
Views: 201

Re: Maximum GPIO frequency from kernel space

The Pi has limited hardware support for regular GPIO reads. You need hardware support as software based reads will be subject to Linux jitter.

I'm not sure if DPI would work. Perhaps SPI.
by joan
Thu Jan 16, 2020 6:20 am
Forum: Troubleshooting
Topic: i2cdetect shows all addresses
Replies: 9
Views: 199

Re: i2cdetect shows all addresses

The GPIO are bust. If something was connected that would have invalidated the test.
by joan
Wed Jan 15, 2020 10:14 pm
Forum: Troubleshooting
Topic: i2cdetect shows all addresses
Replies: 9
Views: 199

Re: i2cdetect shows all addresses

That indicates GPIO 2, 3, 17, and 18 have failed (assuming nothing was connected to those GPIO during the test).
by joan
Wed Jan 15, 2020 8:51 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: Maximum GPIO frequency from kernel space
Replies: 7
Views: 201

Re: Maximum GPIO frequency from kernel space

I've seen people claim more than 20 MHz from user land.

Define stable frequency.
by joan
Wed Jan 15, 2020 2:58 am
Forum: Troubleshooting
Topic: i2cdetect shows all addresses
Replies: 9
Views: 199

Re: i2cdetect shows all addresses

SDA is probably shorted to ground.

Run gpiotest.
by joan
Mon Jan 13, 2020 6:02 am
Forum: Advanced users
Topic: phase opposite hardware pwm
Replies: 4
Views: 156

Re: phase opposite hardware pwm

You can use pigpio waves for this purpose. Just construct a simple wave and send it in repeat mode.
by joan
Sun Jan 12, 2020 10:21 am
Forum: Advanced users
Topic: GPIO.setmode(GPIO.BOARD
Replies: 22
Views: 832

Re: GPIO.setmode(GPIO.BOARD

bruceblosser wrote:
Sun Jan 12, 2020 10:19 am
...
So i really do not get why this is so hard to see ?
We are asking ourselves the same question.
by joan
Fri Jan 10, 2020 11:08 am
Forum: General discussion
Topic: GPIO event detect
Replies: 13
Views: 274

Re: GPIO event detect

RPi.GPIO only allows one active callback per GPIO.

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