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by stefanv
Fri Jun 30, 2017 1:12 pm
Forum: Other projects
Topic: E-Reader Questions
Replies: 1
Views: 237

Re: E-Reader Questions

I can't help with the software, as I haven't tried any packages for this yet, but having just built a Pi tablet , I do have some thoughts on your other questions: 2. Any recommendations on 'tablitifying' the desktop? What Desktop Environment would best suit something like this? The end goal being 'I...
by stefanv
Wed Jun 28, 2017 2:14 pm
Forum: Other projects
Topic: Yet Another Raspberry Pi Tablet
Replies: 6
Views: 655

Yet Another Raspberry Pi Tablet

I've just finished the construction of my Raspberry Pi 3 based tablet. Mine certainly isn’t the first Pi-based tablet, as Googling “Raspberry Pi Tablet” will show, but I think that at 195x112x17.6mm (just a hair bigger than the touchscreen itself) and 484g, it's the smallest and lightest that anyone...
by stefanv
Wed Jun 21, 2017 4:06 pm
Forum: Official Foundation Display
Topic: Need to see more content on your 7in Touch display?
Replies: 7
Views: 1277

Re: Need to see more content on your 7in Touch display?

The touch knows nothing about a changed Screen Resolution. It's still useable with a pen, but not very accurate in case of small touch Icons. Nevertheless, OS Buttons are still useable. It's more a case of whether X deals properly with the mismatch between the touch resolution and screen resolution...
by stefanv
Tue Jun 20, 2017 4:03 pm
Forum: Troubleshooting
Topic: RPi3 Bluetooth and Wifi don't play well together
Replies: 41
Views: 7755

Re: RPi3 Bluetooth and Wifi don't play well together

I'm seeing exactly the same problem with a K380 keywboard and T630 mouse. Either one alone works fine, but if both are active, both work unreliably (such as forever repeating keys, etc.). It would be great to fix this without resorting to either a Bluetooth or WiFi dongle, since one of the nice thin...
by stefanv
Tue Jun 13, 2017 7:04 pm
Forum: Official Foundation Display
Topic: V1.0 has brightness control
Replies: 14
Views: 2537

Re: V1.0 has brightness control

Another possibility, I think, would be to build just the low pass filter (R32, R33, and C74 from ali1234's schematic) on its own little board (one could even use a piece of strip board and through-hole components), connect it to U1's pin 3 and ground on the V1.0 controller board, and drive it from t...
by stefanv
Tue Jun 13, 2017 3:02 pm
Forum: Official Foundation Display
Topic: V1.0 has brightness control
Replies: 14
Views: 2537

Re: V1.0 has brightness control

By the way, I don't think the chip is drawing parasitic power through -SHDN, at least not when the display is lit. It's probably drawing power from the ATTINY's P0 pin (and hence the display only lights up when P0 is high). If it were drawing parasitic power through -SHDN, the display would stay lit...
by stefanv
Tue Jun 13, 2017 2:51 pm
Forum: Official Foundation Display
Topic: V1.0 has brightness control
Replies: 14
Views: 2537

Re: V1.0 has brightness control

I know this is an old thread, but followed the link here from a new thread. :-)

Would it be possible to unsolder pins 4 and 5 of U1, lift up that side of U1 (perhaps while heating pins 1, 2, and 3), and then connect pins 4 and 5 to their correct pads using fine wire?
by stefanv
Fri Jun 09, 2017 1:58 am
Forum: Troubleshooting
Topic: Bad interaction between i2c-rtc overlay and Chromium
Replies: 0
Views: 109

Bad interaction between i2c-rtc overlay and Chromium

I'm posting this in case it saves anyone else some grief. I recently put together a RPi 3 system running Jessie, and added one of those $2 DS1307-based RTC modules from eBay. I found various instructions on-line on how to configure it, generally involving enabling I2C, loading some modules in /etc/m...
by stefanv
Thu Jun 08, 2017 5:23 pm
Forum: C/C++
Topic: Writing clean code isn't hard!
Replies: 138
Views: 5470

Re: Writing clean code isn't hard!

I think it boils down to: Writing clean code isn't hard; cleaning dirty code is. :-)

BTW, the project I've been working on during the course of my career was originally written in B, then ported to C shortly before I came along (but still looked very B-like), and has recently been made C++ compliant.
by stefanv
Thu Jun 08, 2017 5:06 pm
Forum: C/C++
Topic: Writing clean code isn't hard!
Replies: 138
Views: 5470

Re: Writing clean code isn't hard!

Adding a totally pointless prototype just before the actual function stops the warning message! I think that the compiler is correct in complaining. What if you were to call this function from another file? Then you would need the prototype (in a header file #Included by both). The real issue here ...
by stefanv
Thu Jun 08, 2017 4:40 pm
Forum: Official Foundation Display
Topic: Controller Board v1.2
Replies: 7
Views: 844

Re: Controller Board v1.2

Note that the 1.1 board also supports dimming the backlight.
by stefanv
Thu Jun 08, 2017 4:38 pm
Forum: Official Foundation Display
Topic: Need to see more content on your 7in Touch display?
Replies: 7
Views: 1277

Re: Need to see more content on your 7in Touch display?

That "screen" capture isn't really representative, because it shows what's in the frame buffer (1024x614 pixels), not what is actually displayed (1024x614 pixels squished into 800x480 pixels). I.e., it's not really a screen capture, but a frame buffer capture. However, I could see this technique bei...
by stefanv
Thu Jun 08, 2017 4:21 pm
Forum: Other projects
Topic: DIY Power supply units
Replies: 3
Views: 423

Re: DIY Power supply units

If you have enough Pi 3s connected to the power supply, it will meet the minimum load requirements, so you won't need to do anything special. As for how many you can run from one PSU, you need to look at the current limit of the PSU's 5V output, and divide that by the per-Pi current. In my experienc...
by stefanv
Sat Jun 03, 2017 12:54 am
Forum: Raspbian
Topic: Raspbian Logo Just for Fun
Replies: 0
Views: 208

Raspbian Logo Just for Fun

I was just taking a break from my RPi-based project, playing around in Photoshop, combining Tux the Linux penguin (image from https://pixabay.com/en/tux-penguin-animal-cute-linux-158547), and the Raspbian raspberry (as rendered at https://wall.alphacoders.com/big.php?i=293739). Here's what I came up...
by stefanv
Fri May 26, 2017 3:45 pm
Forum: Wolfram Language
Topic: i dont see any point
Replies: 15
Views: 4844

Re: i dont see any point

scruss wrote:Waterloo alum much, Stefan? :D
You could say that. ;-)

I've been working with Maple (and on Maple) since before Mathematica existed.

My point of course is that anyone who was a big Maple fan would also see the point of Mathematica, since it's roughly the same as the point of Maple.
by stefanv
Fri May 12, 2017 5:16 pm
Forum: C/C++
Topic: Writing clean code isn't hard!
Replies: 138
Views: 5470

Re: Writing clean code isn't hard!

Adding a totally pointless prototype just before the actual function stops the warning message! From gcc manual: -Wmissing-prototypes (C and Objective-C only) Warn if a global function is defined without a previous prototype declaration. This warning is issued even if the definition itself provides...
by stefanv
Fri Apr 21, 2017 1:15 am
Forum: Raspbian
Topic: Temporarily disabling USB ports bumps lxpanel to 100% CPU
Replies: 1
Views: 230

Temporarily disabling USB ports bumps lxpanel to 100% CPU

I'm not sure if I should have put this in the Raspbian sub-forum, or one of the hardware ones ... I'm working on an RPi3 application where I need to be able to disable the USB and Ethernet ports (to save about 200mA), which I'm doing using, sudo echo 0x0 > /sys/devices/platform/soc/3f980000.usb/busp...
by stefanv
Fri Mar 10, 2017 5:00 pm
Forum: Wolfram Language
Topic: i dont see any point
Replies: 15
Views: 4844

Re: i dont see any point

stderr wrote:
curlyc wrote:i just dont see why this is a valid thing to learn
Big Maple fan?
If he were a big Maple fan, he would see the point. Mathematica wouldn't be his choice of product to use, but he would know its purpose.

Stefan (big Maple fan)
by stefanv
Sun Oct 23, 2016 12:52 am
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: Issues found while scanning a matrix keyboard
Replies: 14
Views: 1587

Re: Issues found while scanning a matrix keyboard

Boy am I annoyed! The diodes in the keyboard are actually in the opposite direction of what is shown on the schematic. The reason my "diode alone" test worked was because I connected test leads directly to the diode, and of course I connected those the right way around, so of course it worked. Thank...
by stefanv
Sun Oct 23, 2016 12:42 am
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: Issues found while scanning a matrix keyboard
Replies: 14
Views: 1587

Re: Issues found while scanning a matrix keyboard

Okay, I'm beginning to think you're right that there must be something wrong with my code. I've just tried a simple LED blinking program. When the LED is lit, there is 5mA passing through the LED (it's connected via a 270R resistor between a GPIO pin and ground). The output is 3.1V, which means that...
by stefanv
Sat Oct 22, 2016 11:18 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: Issues found while scanning a matrix keyboard
Replies: 14
Views: 1587

Re: Issues found while scanning a matrix keyboard

I guess I should try measuring the voltage. I'll make a simplified version of my program that just does one row and one column and keeps the voltages static. Four diodes would have a drop of 2.4 to 2.8V, so even if the output was 3.3V, the result at the other end with a pull-down resistor would be 0...
by stefanv
Sat Oct 22, 2016 12:51 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: Issues found while scanning a matrix keyboard
Replies: 14
Views: 1587

Re: Issues found while scanning a matrix keyboard

Well, my evidence that the software is working correctly is that it works when I manually touch a row to a column with a jumper. And, as I mentioned, when I switched to pull-low/read-0, it even works through a keyswitch or diode, but not both together.
by stefanv
Fri Oct 21, 2016 4:44 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: Issues found while scanning a matrix keyboard
Replies: 14
Views: 1587

Re: Issues found while scanning a matrix keyboard

Makes sense. I wish they would just specify the no-load output levels, and the impedance, and we can take it from there to figure out the levels with particular loads.
by stefanv
Fri Oct 21, 2016 2:28 pm
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: Issues found while scanning a matrix keyboard
Replies: 14
Views: 1587

Re: Issues found while scanning a matrix keyboard

From GPIO-pads-control: To answer that question I/O ports have two parameters which deal with the output level:  VIL: The maximum low level voltage. (0.8V on the BCM2835)  VIH: The minimum high level voltage. (1.3V on the BCM2835) Can that be right? All the examples that light an LED using a high...

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