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by joan
Wed Sep 18, 2019 5:19 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: PWM to 3.5mm jack
Replies: 7
Views: 130

Re: PWM to 3.5mm jack

PWM on GPIO 40/41 is present on the earlier Pi models. Are you sure you are using the new PWM hardware?
by joan
Wed Sep 18, 2019 11:43 am
Forum: General discussion
Topic: Farnell sells RPi4s with LPDDR4-2400?
Replies: 5
Views: 273

Re: Farnell sells RPi4s with LPDDR4-2400?

Is this a speed thing? I'm not sure if you are suggesting that the Farnell Pi's might be slower than the Welsh variants.
by joan
Wed Sep 18, 2019 9:53 am
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: PWM to 3.5mm jack
Replies: 7
Views: 130

Re: PWM to 3.5mm jack

I have the impression that the PI4 has changed the way audio works. I think I read there is now a separate dedicated PWM chip for audio.
by joan
Wed Sep 18, 2019 9:31 am
Forum: Beginners
Topic: Connecting camera to servo?
Replies: 2
Views: 53

Re: Connecting camera to servo?

To be cautious I'd suggest

Code: Select all

sudo pigpiod
pigs s 5 1000
pigs s 5 2000
which should be fairly safe for any servo.
by joan
Wed Sep 18, 2019 8:39 am
Forum: Beginners
Topic: Control my shutters with a radio emitter?
Replies: 5
Views: 74

Re: Control my shutters with a radio emitter?

Ditto the link.

Anyhow just search for 434 radio on the forum to find an appropriate topic.
by joan
Wed Sep 18, 2019 2:12 am
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: Spidev not working
Replies: 14
Views: 241

Re: Spidev not working

Everything you need for SPI to work seems to be working properly.

Perhaps the tag reader software is buggy?

Can you get more diagnostics from that? E.g. which SPI device is it trying to open?
by joan
Tue Sep 17, 2019 6:26 pm
Forum: Automation, sensing and robotics
Topic: pigpiod processor usage
Replies: 3
Views: 86

Re: pigpiod processor usage

You can disable alerts processing. Use the -m option. http://abyz.me.uk/rpi/pigpio/pigpiod.html

I would suggest you do NOT do that except in extremis.
by joan
Tue Sep 17, 2019 5:34 pm
Forum: Bare metal, Assembly language
Topic: mmap() fails
Replies: 6
Views: 142

Re: mmap() fails

Not withstanding that bare metal people tend to know more than the rest of us but mmap is UNIX derived and not really bare metal.
by joan
Tue Sep 17, 2019 5:05 pm
Forum: Python
Topic: Read serial port using pyserial problem
Replies: 9
Views: 121

Re: Read serial port using pyserial problem

In addition please explain the data being received.

Windows and Linux treat line endings differently. Your problem may be as simple as that.
by joan
Tue Sep 17, 2019 3:35 pm
Forum: Automation, sensing and robotics
Topic: How Many Sensors/Motors Can a Raspberry Pi 3 Handle at Once?
Replies: 6
Views: 150

Re: How Many Sensors/Motors Can a Raspberry Pi 3 Handle at Once?

I have powered multiple small 9g servos from the Pi's 5V pins.

The logic supply required from the 3V3 GPIO to position a servo is insignificant.
by joan
Tue Sep 17, 2019 12:56 pm
Forum: Automation, sensing and robotics
Topic: 2 Stepper Motors; Independent control
Replies: 5
Views: 115

Re: 2 Stepper Motors; Independent control

It sounds like something easy to do on the Pi. Of course you would need an ADC.

How many steps per second per motor? How accurately do the pulses need to be timed? Must they be synchronised? These are the sort of questions which will let you know if an Arduino is more suitable.
by joan
Tue Sep 17, 2019 12:36 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: Spidev not working
Replies: 14
Views: 241

Re: Spidev not working

Compare your command with the commands you were told to use.
by joan
Tue Sep 17, 2019 6:47 am
Forum: Python
Topic: how to measure duration of pulse in python
Replies: 2
Views: 68

Re: how to measure duration of pulse in python

http://abyz.me.uk/rpi/pigpio/examples.h ... ead_PWM_py

That is likely to be the most accurate.
by joan
Mon Sep 16, 2019 5:43 pm
Forum: Automation, sensing and robotics
Topic: pigpiod processor usage
Replies: 3
Views: 86

Re: pigpiod processor usage

That sounds right.

I haven't done measurements for years (since the early Pis).

http://abyz.me.uk/rpi/pigpio/cif.html#gpioCfgClock

I think the time is mainly spent in checking for GPIO level changes.
by joan
Mon Sep 16, 2019 12:04 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: Spidev not working
Replies: 14
Views: 241

Re: Spidev not working

spidev is a Python module.

Are you using Python?

sudo apt install python-spidev python3-spidev
by joan
Mon Sep 16, 2019 10:21 am
Forum: C/C++
Topic: /dev/gpiomem usage and limitations
Replies: 1
Views: 45

Re: /dev/gpiomem usage and limitations

/dev/gpiomem only gives access to the GPIO peripheral.

To access the other peripherals you will have to use /dev/mem.
by joan
Sun Sep 15, 2019 10:30 am
Forum: General discussion
Topic: can I create my own PI card?
Replies: 8
Views: 273

Re: can I create my own PI card?

Highly unlikely unless you can afford to pay for several thousand units. If your application is not Pi specific there are plenty of other boards you could use.
by joan
Sat Sep 14, 2019 1:11 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: Pi4 and bcm_host_get_peripheral_address()
Replies: 3
Views: 88

Re: Pi4 and bcm_host_get_peripheral_address()

It's the address I pass to Linux mmap.
by joan
Sat Sep 14, 2019 9:49 am
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: Pi4 and bcm_host_get_peripheral_address()
Replies: 3
Views: 88

Re: Pi4 and bcm_host_get_peripheral_address()

Don't know if it has been updated or not.

BCM2711/Pi4B peripherals base address 0xFE000000.
by joan
Fri Sep 13, 2019 4:03 pm
Forum: Beginners
Topic: How does GPIOs work in raspbian?
Replies: 9
Views: 234

Re: How does GPIOs work in raspbian?

All the GPIO have multiple modes.

Have a look at wiringPi's gpio utility.

man gpio
by joan
Fri Sep 13, 2019 8:18 am
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: Spidev not working
Replies: 14
Views: 241

Re: Spidev not working

You have provided no evidence that SPI is not working.

Why do you think SPI is not working?
by joan
Thu Sep 12, 2019 9:32 am
Forum: HATs and other add-ons
Topic: DHT11 add-ons to an existing ADCPi board
Replies: 1
Views: 51

Re: DHT11 add-ons to an existing ADCPi board

That should be fine. The ADCPi boards only use GPIO2/3 (for the I2C connection).

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