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Author Topic: Useful things with Raspberry Pi  (Read 272546 times)
KJ6DRG
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« Reply #30 on: April 26, 2017, 07:28:32 PM »

Anyone simply use it as a desktop computer? I built a nice Intel i5 quad core machine, 8 gb of ram, SSD, fast as all get out (well, compared to anything I've ever owned previously) but I honestly have a lot of fun just plugging into my monitor and using Raspian Pixel. So basic, so clean, and so capable of running fldigi Smiley
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WE6EE
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« Reply #31 on: June 07, 2017, 09:12:30 PM »

I'm a big fan of the RPi platform, and use one to enable remote-access to my IC-7300 -- using no additional hardware at all. I just plug the USB into the Pi and I have a little 5W machine that can forward control and audio to a client anywhere on the Internet. Because it runs Linux, it's no trouble to set it up so I can securely access it via ssh and even forward network ports. It works really well.

I'm still looking for a solution for forwarding audio that I like better than Pulseaudio. Options on Linux that use codecs that are robust over the internet are limited.

I also built a device for acting as a dead-man's switch to my rig, should I lose network contact. It talks to the RPi using the I2C pins. Here's a post I made about it a few weeks ago:

http://www.eham.net/ehamforum/smf/index.php/topic,115027.0.html

-- dave WE6EE
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WO7R
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« Reply #32 on: June 14, 2017, 08:32:51 AM »

Any ham device that is USB or RS232 with a sufficiently "open" (aka "documented") interface can be turned into an internet enabled device with a Raspberry Pi.  In other words, if you can send and receive ASCII character strings to control the device, you're basically there.

Most RS232 devices (and all that I actually own) run well off of a suitable USB-to-RS232 adapter (they are out there, not expensive).

Devices I am doing this on include:  Arduinos, Sainsmart "dry contact switches" (aka relays), and (soon) a USB-controlled switchable USB hub (so I can turn USB devices on and off individually without being in the room).

Devices I will be doing this on include:  Green Heron Controllers (bought mine before their ethernet versions became available).

Devices I could do if I could get the protocol information:  Alpha 9500.  This one probably stays on Windows.

I have also recently obtained a WinKeyer.  I probably can have that one on the "Pi" as well.

Beyond direct ham radio usage, I routinely have SAMBA (looks like Windows File Sharing) and LIGHTTPD (Web Serving) on my Pis. 

The latter is important:  A simple, basic web page will allow me to access and control any RS232/USB device I managed to support from the Pi.  This also means the device can be controlled from a phone or a tablet, freeing me from having to control everything from a PC.

The former allows me to have a lot of things in a known location.  By today's standards, the SSD on the Pi isn't very big, but as long as you aren't trying to store a lifetime of photos on them, storage in a typical Pi SSD (even 8 GB) is plenty.
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N3QE
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« Reply #33 on: June 14, 2017, 09:35:03 AM »

I do not use it as a desktop computer, but it's real nice as a Wi-Fi connected box to allow remote control via the GPIO pins.

It's the GPIO pins, and their easy access from Python and Perl and other scripting languages, that really make it useful.

I have already put mine to use doing remote antenna switching and for SO2R relay switching.
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WO7R
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« Reply #34 on: June 14, 2017, 12:16:15 PM »

How do you handle the voltage switching?

One reason I have been in favor of Arduinos over Pis for actual device control of relays and such things is that Arduinos do everything in 5v, which is still what most other devices want to see.  As I read the spec, all the stuff coming out of the Pi is 3.3 v.

The other reason is that I am much more confident about "near real time" control with Arduino as it has no significant services running.

What I do is deploy inexpensive Arduinos and operate them over the USB port and let the Pi put up the web page.

How do you overcome those issues, or do you have slow speed stuff that allows you to ignore it?  Does the I2S stuff help in this wise once you account for the voltage?
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N3QE
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« Reply #35 on: June 16, 2017, 08:42:58 AM »

How do you handle the voltage switching?

3.3V GPIO outputs from the Raspberry Pi, drive a ULN2003 that drive the 12V relays.

Quote
One reason I have been in favor of Arduinos over Pis for actual device control of relays and such things is that Arduinos do everything in 5v, which is still what most other devices want to see.  As I read the spec, all the stuff coming out of the Pi is 3.3 v.

You have to keep in mind that the "classic" TTL hi output is very wimpy. Even though the Vcc was 5V, the TTL hi output would wimp out and was only guaranteed to put out 2.4V into sub-milliamp loads. So if you are using modern 3.3V CMOS logic, which are amazingly stiff hi-current outputs in comparison to 5V TTL, you will be able to drive TTL-level drivers no problem.

Below is excerpt from TI SN7400 data sheet showing how wimpy classic TTL was at drive in HI.



Quote
The other reason is that I am much more confident about "near real time" control with Arduino as it has no significant services running.

What I do is deploy inexpensive Arduinos and operate them over the USB port and let the Pi put up the web page.

How do you overcome those issues, or do you have slow speed stuff that allows you to ignore it?  Does the I2S stuff help in this wise once you account for the voltage?

Raspberry Pi is lightning fast. CPU is running at hundreds of MHz. Never saw any of these speed issues you are talking about. As a remote relay driver responding to WiFi UDP packets it always responds in milliseconds, faster than the relay mechanical throw time even. I think the limiting factor in my use is millisecond-range WiFi latency and has nothing to do with the processor or the code running on it.

Another platform I like even better than Raspberry Pi for remote Wi-Fi control to GPIO pins, is the ESP8266. I love the ESP8266, about $8. I think you can program it using Arduino toolchain but I use the quickie LUA scripting language that comes built into the ESP8266 and it is a joy to use. The ESP8266 modules I use come packaged like a "large DIP chip" making them very easy to put into perfboard for all sorts of fun projects. Power draw is very low compared to Raspberry Pi. Unlike the Raspberry Pi it doesn't have a place to plug in a keyboard and a video screen but then again this is for IoT stuff, not "little PC" stuff.


« Last Edit: June 16, 2017, 08:55:46 AM by N3QE » Logged
WB8LZR
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« Reply #36 on: July 01, 2017, 01:16:25 PM »


...

Raspberry Pi is lightning fast. CPU is running at hundreds of MHz. Never saw any of these speed issues you are talking about. As a remote relay driver responding to WiFi UDP packets it always responds in milliseconds, faster than the relay mechanical throw time even. I think the limiting factor in my use is millisecond-range WiFi latency and has nothing to do with the processor or the code running on it.

Another platform I like even better than Raspberry Pi for remote Wi-Fi control to GPIO pins, is the ESP8266. I love the ESP8266, about $8. I think you can program it using Arduino toolchain but I use the quickie LUA scripting language that comes built into the ESP8266 and it is a joy to use. The ESP8266 modules I use come packaged like a "large DIP chip" making them very easy to put into perfboard for all sorts of fun projects. Power draw is very low compared to Raspberry Pi. Unlike the Raspberry Pi it doesn't have a place to plug in a keyboard and a video screen but then again this is for IoT stuff, not "little PC" stuff.



Yes, I'm a big fan of that form factor.  I'm using the Photon (from particle.io) - which is a very similar type of device, when compared to the ESP8266.  But the Photon runs a little higher in cost (about twice what the ESP8266 goes for), so I've been thinking about giving the ESP8266 a try for the next project.  The Photon has a big library for almost any functionality, and they're constantly adding more useful things,  it uses a modified FreeRTOS "OS" - and multiple "threads".  How does the ESP compare on those scores?

As far as the RPi goes, sometimes it is overkill.  That's where the Photon (or something even smaller) comes into play.  There's not that much wrong with the Pi (I love those things) - but the complicated software it runs (also known as Linux) - can have problems associated with it, and that could impact reliability.  Although - those problems are usually drivers, and over time are fixed. 

« Last Edit: July 01, 2017, 01:20:38 PM by WB8LZR » Logged
N3QE
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« Reply #37 on: July 11, 2017, 12:09:43 PM »

Yes, I'm a big fan of that form factor.  I'm using the Photon (from particle.io) - which is a very similar type of device, when compared to the ESP8266.  But the Photon runs a little higher in cost (about twice what the ESP8266 goes for), so I've been thinking about giving the ESP8266 a try for the next project.  The Photon has a big library for almost any functionality, and they're constantly adding more useful things,  it uses a modified FreeRTOS "OS" - and multiple "threads".  How does the ESP compare on those scores?

The ESP8266 LUA environment is event driven by IO completion and/or timer expirations and in that way you can keep multiple things in flight. They describe it both in terms of couroutines and threads. It's not quite a full multitasking OS because each coroutine/thread must yield at its I/O wait points etc. But it is similar to a lot of Real-time operating systems I've used in the past. I'm not sure I'd call LUA an operating system but it is more than just a scripting language.

Particle seems to be a little broader than LUA but there are LUA libraries for doing many similar things.

It can also be programmed in the Arduino IDE that has similar ideas as well as libraries but not quite the same words.
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K6TTE
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« Reply #38 on: September 11, 2017, 07:38:24 PM »

There are a ton of projects out there for the Raspberry Pi, the 3 in particular.  I recently implemented an email server and a VPN server on a couple of them.  A live backup email server and a super cluster are other projects on my list.

If you have an android device, search for "Proyectos Pi" in the Play Store.  Don't worry, you can select English once you start the app.  It has a large number of interesting projects.

Enjoy! 
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