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by liudr
Thu Mar 19, 2020 1:18 am
Forum: General discussion
Topic: Running Khan academy (mostly full-screen videos) with RPI4 ?
Replies: 2
Views: 403

Re: Running Khan academy (mostly full-screen videos) with RPI4 ?

Thank you Botspot! I made all the changes you suggested and I can now play videos smoothly enough without crashing now. Switching from windowed to full screen still takes a couple of seconds and buffering is visible but I think it's a usable system, considering 3B was the first bearable desktop expe...
by liudr
Tue Mar 17, 2020 10:00 pm
Forum: General discussion
Topic: Running Khan academy (mostly full-screen videos) with RPI4 ?
Replies: 2
Views: 403

Running Khan academy (mostly full-screen videos) with RPI4 ?

I've set up my rpi3+ for Khan academy (khanacademy.org) but it is slow and the video sometimes freezes the pi if I play it in full-screen 1080p resolution. Has anyone tried it with rpi4, with what amount of RAM, how do you like it running on rpi4? Thanks.
by liudr
Fri Sep 13, 2019 8:21 pm
Forum: Beginners
Topic: How does GPIOs work in raspbian?
Replies: 9
Views: 727

Re: How does GPIOs work in raspbian?

Awesome help! If I understand correctly, RPi.GPIO looks similar to arduino. gpiozero is more OOP and tries to hide more details. I'll try RPi.GPIO first. Just have to figure out what "GPIO25" means, BCM, or other mode.
by liudr
Fri Sep 13, 2019 4:14 pm
Forum: Beginners
Topic: How does GPIOs work in raspbian?
Replies: 9
Views: 727

Re: How does GPIOs work in raspbian?

Thanks. Will investigate the gpio command. I'll just pick one that is not I2C, not second SPI, not alt. hardware-UART, etc. There should be a few left that are less feature-ful I guess :lol: Also the inner row of pins are preferred to save time on board routing. Will get back to report how it works ...
by liudr
Fri Sep 13, 2019 3:57 pm
Forum: Beginners
Topic: How does GPIOs work in raspbian?
Replies: 9
Views: 727

Re: How does GPIOs work in raspbian?

It depends whether you code an exception handler to reset things. Else they'll stick in the last active state. Exactly what I was seeking (and secretly hoping for) in a concise way! Thank you! Some background: I was hoping to have rpi0w powered by a usb hub, not via its own microUSB ports but via h...
by liudr
Fri Sep 13, 2019 3:31 pm
Forum: Beginners
Topic: How does GPIOs work in raspbian?
Replies: 9
Views: 727

How does GPIOs work in raspbian?

So from a resource stand point, if I were to use a python module to manipulate the states of GPIOs, after my script ends, will the GPIO resource be in anyway reset to default, or will they stay the way I set it in my script? Same for manipulating GPIOs with say some sort of bash command etc. The rea...
by liudr
Wed Sep 11, 2019 4:05 am
Forum: Beginners
Topic: Is this the correct way to use mini-UART on BT and PL011 UART on pins 14/15?
Replies: 1
Views: 262

Re: Is this the correct way to use mini-UART on BT and PL011 UART on pins 14/15?

Can someone with device tree experience check please? Thanks.
by liudr
Sun Sep 08, 2019 11:49 pm
Forum: Beginners
Topic: Is this the correct way to use mini-UART on BT and PL011 UART on pins 14/15?
Replies: 1
Views: 262

Is this the correct way to use mini-UART on BT and PL011 UART on pins 14/15?

I only need PL011 UART on pins 14/15 to talk with arduino in my project so I disabled bt, enabled hardware serial, and disabled serial console. This works but something else is breaking my system, causing wifi to refuse to connect, which might be related to BT being considered as a network interface...
by liudr
Sun Sep 08, 2019 11:35 pm
Forum: Python
Topic: Reading SPI SRAM with python
Replies: 1
Views: 335

Re: Reading SPI SRAM with python

It turns out that at 2Mbaud rate with hardware serial, rpi 0w loses a few bytes in the transmission. I used 1Mbaud at my target data transfer quantity and frequency and that worked.
by liudr
Sun Sep 08, 2019 1:54 am
Forum: Python
Topic: Reading SPI SRAM with python
Replies: 1
Views: 335

Reading SPI SRAM with python

I have a project that needs pi to read bursts of data from arduino at a high rate and large quantity. Arduino doesn't have enough memory to hold all data so it needs a fast interface to send to pi. The fastest way I can think of is to have arduino fill an SPI SRAM module with data, inform pi via ser...
by liudr
Wed Sep 04, 2019 9:32 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: Any settings to hold pi from booting with a GPIO pin?
Replies: 1
Views: 243

Any settings to hold pi from booting with a GPIO pin?

I'm interested in running a pi 0w on a computer USB port with power running through an arduino that acts as a USB device. I could add a transistor to turn on PI when arduino finishes USB enumeration so it could receive 500mA. But instead, if there is a setting I can enable to hold pi in a kind of re...
by liudr
Wed Sep 04, 2019 3:45 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: Enable/disable SPI without raspi-config or reboot?
Replies: 6
Views: 1578

Re: Enable/disable SPI without raspi-config or reboot?

Maybe I should just stick with hardware solution: 54AHCT125 quad buffer (3V->5V logic converter) with 3-state outputs. It has output enable. I can have two of them convert pi's MOSI, SCK, from 3V to 5V, along with GPIO25 to reset Arduino and TX (serial) to Arduino RX. On Arduino side, switch off OE ...
by liudr
Wed Sep 04, 2019 3:03 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: Enable/disable SPI without raspi-config or reboot?
Replies: 6
Views: 1578

Re: Enable/disable SPI without raspi-config or reboot?

I'm confused now as I'm not nix wiz. I'm not familiar with dtparam messages. What are loading orders and do the dtparam on or off work?
by liudr
Tue Sep 03, 2019 1:38 am
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: Enable/disable SPI without raspi-config or reboot?
Replies: 6
Views: 1578

Enable/disable SPI without raspi-config or reboot?

The reason I want SPI enabled is because I connected an arduino to it via level shifters so I can upload code to it using avrdude and spi programmer mode. It works very nicely since rpi 0w has only a single USB port and I won't waste it on arduino usb bootloader. The reason I want RPI SPI disabled i...
by liudr
Wed Oct 10, 2018 2:05 pm
Forum: General discussion
Topic: Load same history every time
Replies: 10
Views: 1391

Re: Load same history every time

tpyo kingg wrote:
Mon Oct 08, 2018 2:54 pm
That would go in the user's .bashrc file.
Thanks.
by liudr
Mon Oct 08, 2018 2:29 pm
Forum: General discussion
Topic: Any PC software that can make backup images of RPI?
Replies: 1
Views: 478

Any PC software that can make backup images of RPI?

I've been using "Paragon backup and recovery 2014" to back up my RPIs until the more recent distro that breaks it (restored images wouldn't boot). I can use the win32 disk imager if I have to, dumping sectors instead of recording drive content and skipping over empty spaces and any memory swap files...
by liudr
Mon Oct 08, 2018 2:24 pm
Forum: General discussion
Topic: Load same history every time
Replies: 10
Views: 1391

Re: Load same history every time

Rather than overwrite .bash_history another way would be to unset the $HISTFILE variable: unset HISTFILE; history -r /home/pi/Documents/cmd_history.txt It's fewer steps but that may not matter so much. Thanks. I'll try this as well. Will this have to be done just once per user account or included i...
by liudr
Mon Oct 08, 2018 2:20 pm
Forum: General discussion
Topic: Load same history every time
Replies: 10
Views: 1391

Re: Load same history every time

Include the command to run your “clean-up history” script in your predefined command history. Then the user can run that command anytime when he/she feels there is a need. If you need to have the command history always only remember the predefined commands, nothing else. Then you may create a scrip...
by liudr
Fri Oct 05, 2018 5:20 am
Forum: General discussion
Topic: Load same history every time
Replies: 10
Views: 1391

Re: Load same history every time

Background: The RPI is sealed in a waterproof box with a display and a few push buttons around the box's sides. It's to be used in the field where people may wear gloves and have water and dust and probably grease. They need to select what command to run and not have to run them in any particular se...
by liudr
Fri Oct 05, 2018 3:44 am
Forum: General discussion
Topic: Load same history every time
Replies: 10
Views: 1391

Load same history every time

I'm trying to have a pre-defined list of commands in history each time I start terminal so I can quickly do a few tasks with the up arrow and enter buttons only. I tried this in .bashrc but that didn't work at first: history -c;history -r /home/pi/Documents/cmd_history.txt Whatever I did before clos...
by liudr
Fri Sep 21, 2018 1:30 am
Forum: General discussion
Topic: Shut down rpi with a keyboard key combo
Replies: 21
Views: 6232

Re: Shut down rpi with a keyboard key combo

Is this any use: https://www.raspberrypi.org/forums/viewtopic.php?f=29&t=206921#p1280779 It won't physically remove power, but nothing internal to the Pi will do that without extra/external hardware. However it does put the Pi into a state whereby you can just safely "pull the plug". BTW: Note that...
by liudr
Wed Sep 19, 2018 9:31 pm
Forum: General discussion
Topic: Shut down rpi with a keyboard key combo
Replies: 21
Views: 6232

Re: Shut down rpi with a keyboard key combo

What if your GUI is focused on a file browser? Will that key sequence delete an important file without confirmation? What if you're focused on a terminal windows that is running a Python code? :lol: I'm looking for a method that will initiate a shutdown process regardless which window gets the focus...
by liudr
Wed Sep 19, 2018 7:29 pm
Forum: General discussion
Topic: Shut down rpi with a keyboard key combo
Replies: 21
Views: 6232

Shut down rpi with a keyboard key combo

I've seen plenty of projects describing how to shut down rpi with a push button connected to a GPIO pin and running a python script to catch the button push. I thought why not setting up a keyboard combo for shutdown or other stuff? If I can do that under GUI, I can replace the real keyboard with an...
by liudr
Thu Sep 06, 2018 4:14 am
Forum: Python
Topic: Trying to make python import work
Replies: 9
Views: 1325

Re: Trying to make python import work

Yes, I like the duck type where you can just pass an object to a function to be used. It's more flexible than C++. Anyway, that doesn't help me with the separate namespace issues. I want variables and functions stored in other files to be incorporated into the main name space like they were defined ...

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