I bought a Pi4 and now ...

Where can I get the best training on-line to work with the Pi4 hardware
and learn to code for it too ?

I want to make a remote control vehicle with a camera that I can drive
around my house. I am handicapped and do not get around well and just
would like to see what is going on in other parts of the house.

Aoli wrote:

> I want to make a remote control vehicle with a camera that I can drive
> around my house.

Are you wanting to use a kit, or build it from scratch?

<https://www.instructables.com/Raspberry-Pi-Remote-Controlled-Car-1/>

On Sun, 20 Jun 2021 21:38:36 +0100, Andy Burns wrote:

> Aoli wrote:
>
>> I want to make a remote control vehicle with a camera that I can drive
>> around my house.
>
> Are you wanting to use a kit, or build it from scratch?
>
> <https://www.instructables.com/Raspberry-Pi-Remote-Controlled-Car-1/>

Do you know how to:
- use the Linux OS
- any programming languages, and if so which?
- what sort of programs have you written on other computers?

Knowing this stuff will let us provide more relevant help.

--
Martin | martin at
Gregorie | gregorie dot org

Thank you for your responses.

I can do from scratch or kit, from scratch I would need some guidance
but I do have tools that might be needed except for 3D printing which I
do not do.

I am slightly familiar with Linux but of the higher forms of such like
Mint with a graphical interface.

I can program in C and a little Java. Python looks pretty straight
forward to me. I am proficient programing in Visual Basic Classic (VB6).

What language would I need ?

Martin Gregorie wrote:
> On Sun, 20 Jun 2021 21:38:36 +0100, Andy Burns wrote:
>
>> Aoli wrote:
>>
>>> I want to make a remote control vehicle with a camera that I can drive
>>> around my house.
>>
>> Are you wanting to use a kit, or build it from scratch?
>>
>> <https://www.instructables.com/Raspberry-Pi-Remote-Controlled-Car-1/>
>
> Do you know how to:
> - use the Linux OS
> - any programming languages, and if so which?
> - what sort of programs have you written on other computers?
>
> Knowing this stuff will let us provide more relevant help.
>
>

I would be nice to operate the vehicle from a tablet (hopefully android).
Tablet is light weight, easy for me to hold and relatively inexpensive.

Aoli wrote:
>
> Thank you for your responses.
>
> I can do from scratch or kit, from scratch I would need some guidance
> but I do have tools that might be needed except for 3D printing which I
> do not do.
>
> I am slightly familiar with Linux but of the higher forms of such like
> Mint with a graphical interface.
>
> I can program in C and a little Java.  Python looks pretty straight
> forward to me.  I am proficient programing in Visual Basic Classic (VB6).
>
> What language would I need ?
>
>
>
> Martin Gregorie wrote:
>> On Sun, 20 Jun 2021 21:38:36 +0100, Andy Burns wrote:
>>
>>> Aoli wrote:
>>>
>>>> I want to make a remote control vehicle with a camera that I can drive
>>>> around my house.
>>>
>>> Are you wanting to use a kit, or build it from scratch?
>>>
>>> <https://www.instructables.com/Raspberry-Pi-Remote-Controlled-Car-1/>
>>
>> Do you know how to:
>> - use the Linux OS
>> - any programming languages, and if so which?
>> - what sort of programs have you written on other computers?
>>
>> Knowing this stuff will let us provide more relevant help.
>>
>>
>

On Mon, 21 Jun 2021 11:52:49 -0700, Aoli wrote:

> Thank you for your responses.
>
> I can do from scratch or kit, from scratch I would need some guidance
> but I do have tools that might be needed except for 3D printing which I
> do not do.
>
> I am slightly familiar with Linux but of the higher forms of such like
> Mint with a graphical interface.
>
Its a good idea to get familiar with bash, the default command language,
because you will probably find yourself writing shell scripts to handle
system management tasks, backups, etc.
> I can program in C and a little Java. Python looks pretty straight
> forward to me. I am proficient programing in Visual Basic Classic
> (VB6).
>
C, Java, Python are good, though I'm uncertain how similar the Windows C
support library is to the the C Standard Library, as used in all
UNIX/Linux systems. Its over 20 years since I compiled a program under
Windows. Java is, of course much the same under any OS.

BASIC is very little used by RPi programmers; most of those who used to
write BASIC would now write Python and, in any case only the .NET
flavours of BASIC seem to be widely supported on RPis.

Depending how you prefer to learn stuff, the "RaspberryPi User Guide" may
help. You may also find "Linux in a Nutshell" useful for understanding
how Linux and its scripting language works. It also explains how help
systems like 'apropos' and the 'man' command (both used to find utility
programs and how to use them) are best used. There are a LOT of these:
the UNIX/Linux world works on the principle that a program should do one
thing and do it well and that you can do more complex things by
connecting a number of these utility programs so that the output of one
feeds the next in a 'pipeline'.

O'Reilly books are also good, though some are fairly pricey. That said,
if you're going to write a lot of C, then any of the C system programing
books for UNIX/Linux are good to have.

It also helps to understand regular expressions (which you may already
understand by using them in Java or C programs) because a lot of command
line tools and editors use regexes as parameters.

There are a lot of text editors: 'gedit', either naked or run via the
lightweight 'geany' IDE is not bad, but some of the others ('emacs',
'microemacs' and 'vi') are a lot more powerful and worth looking at to
see which you prefer.
I have David Curry's "Unix Systems Programming for SvR4" and wouldn't be
without it, though its quite a brick: its quite old, but still very
useful.

--
Martin | martin at
Gregorie | gregorie dot org

On 6/21/21 12:58 PM, Aoli wrote:
>
> I would be nice to operate the vehicle from a tablet (hopefully android).
> Tablet is light weight, easy for me to hold and relatively inexpensive.
>
> Aoli wrote:
>>
>> Thank you for your responses.
>>
>> I can do from scratch or kit, from scratch I would need some guidance
>> but I do have tools that might be needed except for 3D printing which
>> I do not do.
>>
>> I am slightly familiar with Linux but of the higher forms of such like
>> Mint with a graphical interface.
>>
>> I can program in C and a little Java.  Python looks pretty straight
>> forward to me.  I am proficient programing in Visual Basic Classic (VB6).
>>
>> What language would I need ?
>>
>>
>>
>> Martin Gregorie wrote:
>>> On Sun, 20 Jun 2021 21:38:36 +0100, Andy Burns wrote:
>>>
>>>> Aoli wrote:
>>>>
>>>>> I want to make a remote control vehicle with a camera that I can drive
>>>>> around my house.
>>>>
>>>> Are you wanting to use a kit, or build it from scratch?
>>>>
>>>> <https://www.instructables.com/Raspberry-Pi-Remote-Controlled-Car-1/>
>>>
>>> Do you know how to:
>>> - use the Linux OS
>>> - any programming languages, and if so which?
>>> - what sort of programs have you written on other computers?
>>>
>>> Knowing this stuff will let us provide more relevant help.
>>>
>>>
>>
>

There are numerous tutorials at adafruit.com and the free e-mag 'magpi'
at raspberrypi.org which would be helpful. The main language for pi is
python. It should not be too difficult to control from a tablet - that
would just mean you would need a pi onboard for control over wifi or bt.

On Mon, 21 Jun 2021 11:52:49 -0700, Aoli <Aoli@Aoli.com> declaimed the
following:

>
>I am slightly familiar with Linux but of the higher forms of such like
>Mint with a graphical interface.
>
The R-Pi, with the default OS, comes out of the box with a graphical
interface... It does require one use an HDMI connected monitor/TV, and a
USB keyboard/mouse... Or one enables the VNC server and connects to it over
network using a VNC client program.

>I can program in C and a little Java. Python looks pretty straight
>forward to me. I am proficient programing in Visual Basic Classic (VB6).
>
>What language would I need ?
>
You won't like this: Which ever one satisfies your requirements -- you
could install GNAT and code in Ada; or suck up a few GB installing
Lazarus/FreePascal.

Python was considered the "native" (as in: meant for beginners)
language for the R-Pi...

Thing is, your requirements are so high-level that one can't really
declare for any language. At the very least, you are looking at a
multi-threaded application, if not multi-process system (threads exist
within a single process, and depending on implementation, can share
information easily; multi-process will require designing some interprocess
communication system/protocol -- unfortunately, the only OSs for which I
was comfortable in IPC are AmigaOS (message ports: linked lists created by
processes to which other processes can append "messages"; since the Amiga
used a flat address space, all processes could access any memory --
messages tended to contain just a pointer to a buffer) and [Open]VMS
(mailboxes to which processes can write/read).

Take into account that Linux is not a "real-time" OS; an RT kernel just
makes it more responsive without truly being real-time.

The process that handles the drive motors is probably going to run at a
higher priority than one that is handling a camera and relaying video over
WiFi. Higher than both of those might be the process that handles command
receipt and return telemetry. It should spend a lot of time just waiting
for commands, and some time packaging telemetry packets -- no busy loops,
since that would interfere with lower level processes (a busy loop could
totally block out the motor control process from responding to forwarded
STOP commands).

You may even find that you only want to run the user-interface on the
R-Pi, with it sending commands to multiple microcontrollers (Arduino, TIVA
C, AdaFruit Metro [which uses CircuitPython natively, but can have an
Arduino compatible loader installed]).

Some books that might be of import:

Real-Time Systems and Programming Languages: Ada, Real-Time Java and
C/Real-Time POSIX 4th Ed (Alan Burns/Andy Wellings, 2009 Addison-Wesley)

Embedded Linux Primer 2nd Ed (Christopher Hallinan, 2011 Prentice-Hall)

{Interesting: both Addison-Wesley and Prentice-Hall appear to be owned by
Pearson}

--
Wulfraed Dennis Lee Bieber AF6VN
wlfraed@ix.netcom.com http://wlfraed.microdiversity.freeddns.org/

On Mon, 21 Jun 2021 21:49:01 -0400, Dennis Lee Bieber
<wlfraed@ix.netcom.com> declaimed the following:

>Embedded Linux Primer 2nd Ed (Christopher Hallinan, 2011 Prentice-Hall)
>
On second thought -- you can probably ignore this one; it is mostly
about configuring and building Linux kernels, and device driver stuff.

Not Linux-based, but of possible use for algorithms:

Make: Arduino Bots and Gadgets
Make: Making Simple Robots
Make an Arduino-Controlled Robot

Hands-On RTOS with Microcontrollers
(FreeRTOS on an STM32, but should port to other ARM processors)

--
Wulfraed Dennis Lee Bieber AF6VN
wlfraed@ix.netcom.com http://wlfraed.microdiversity.freeddns.org/

On 21/06/2021 19:58, Aoli wrote:
>
> I would be nice to operate the vehicle from a tablet (hopefully android).
> Tablet is light weight, easy for me to hold and relatively inexpensive.
> Consider writing your user interface in e.g. php html and javascript
then you can use a browser on the tablet to access the pi.

You probably will need a more 'native' language on te pi. Python or C
really

--
To ban Christmas, simply give turkeys the vote.

On Mon, 21 Jun 2021 21:49:01 -0400, Dennis Lee Bieber wrote:

> You won't like this: Which ever one satisfies your requirements
-- you
> could install GNAT and code in Ada; or suck up a few GB installing
> Lazarus/FreePascal.
>
> Python was considered the "native" (as in: meant for beginners)
> language for the R-Pi...
>
> Thing is, your requirements are so high-level that one can't really
> declare for any language. At the very least, you are looking at a
> multi-threaded application, if not multi-process system (threads exist
> within a single process, and depending on implementation, can share
> information easily; multi-process will require designing some
> interprocess communication system/protocol -- unfortunately, the only
> OSs for which I was comfortable in IPC are AmigaOS (message ports:
> linked lists created by processes to which other processes can append
> "messages"; since the Amiga used a flat address space, all processes
> could access any memory -- messages tended to contain just a pointer to
> a buffer) and [Open]VMS (mailboxes to which processes can write/read).
>
If you are going to multi-thread, normally I'd suggest going for Java,
which also has a decent GUI system, SWING, especially using using the 3rd
party RiverLayout layout manager from se.datadosen.

Disclaimer: I know thus works v. well in kit like Lenovo laptops but
haven't yet installed Java on an RPi, so have no idea of the likely
performance or compile speeds.

OTOH, if you'd rather go multi-process, then writing a set of co-
operating processes in C that communicate through a block of shared
memory and use semaphores to co-ordinate access is fairly easy,
especially if you have the UNIX Systems Programming book I recommended.

A third way to go is to write a set of small, single threading C
processes, each carrying out a single, well-defined part of the overall
task.

One of these processes owns a block of shared memory and manages access
to it: the blocks of incoming do not move once they are loaded into the
shared memory by a loader process, where then remain until all operations
on them are complete, and an exporter process has done the final
operation and requested them to be deleted from shared memory.

The other worker processes operate by requesting access to a data block,
which is locked as they get passed its address. After they've done their
thing the worker tells the shared memory owner to release the last block
and requests another: each stored block is either 'available' or marked
as allocated to a worker process.

All interprocess communication is done by standard UNIX message passing,
and is handled by the standard C poll() mechanism, which is brilliant for
handling this sort of message queueing.

This sort of multi-process data handling stream works really well and is
quite simple to implement: I designed and implemented a large, high
performance ETL system, running on DEC Alphaserver kit, that transformed
incoming data and loaded it into a data warehouse using this approach. It
easily exceeded the stated performance requirements and, because each
step was handled by a separate, single threaded process, the code was
both simple and secure.

> The process that handles the drive motors is probably going to run at a
> higher priority than one that is handling a camera and relaying video
> over WiFi. Higher than both of those might be the process that handles
> command receipt and return telemetry. It should spend a lot of time just
> waiting for commands, and some time packaging telemetry packets -- no
> busy loops, since that would interfere with lower level processes (a
> busy loop could totally block out the motor control process from
> responding to forwarded STOP commands).
>
> You may even find that you only want to run the user-interface on the
> R-Pi, with it sending commands to multiple microcontrollers (Arduino,
> TIVA C, AdaFruit Metro [which uses CircuitPython natively, but can have
> an Arduino compatible loader installed]).
>
Could also be a good place to use PICAXE chips (despite their rather
horrid compiled, unsigned intreger BASIC (but at least the PICAXE BASIC
compiler runs well on an RPI 2B) or even a RaspberryPi PICO.

Don't forget the standard C poll() function I mentioned earlier, which
can handle responses from microcontrollers as well as from other
processes. See 'man 2 poll' for details.

--
Martin | martin at
Gregorie | gregorie dot org

On Tue, 22 Jun 2021 13:53:54 -0000 (UTC), Martin Gregorie
<martin@mydomain.invalid> declaimed the following:

>Could also be a good place to use PICAXE chips (despite their rather
>horrid compiled, unsigned intreger BASIC (but at least the PICAXE BASIC
>compiler runs well on an RPI 2B) or even a RaspberryPi PICO.
>
I could have suggested the Parallax Propeller chip. An extremely weird
microcontroller.

8 "cogs" (cores) running in lockstep, all sharing the 32 GPIO lines.
Nominally a core runs Propeller BASIC interpreter which accesses compiled
code from external memory (there is controller that rotates from cog to cog
allowing access to external memory), but can be loaded with Propeller
assembly code. I believe there is also a C compiler available.

The former Parallax BASIC-Stamps (if any are still stocked) are way too
expensive to consider. One could (in the US at least) buy 7-8 TIVA C
TM4C123G Launchpads for the cost of BS2p. Launchpads are ARM Cortex M4
floating point. The 123 is the slower one, at 80MHz; 256kB flash, 32kB RAM,
and a 2kB EEPROM; 12-bit ADC (2x), and way too many timers (6x64-bit, each
of which can be split into a pair of 32-bit timers, AND 6x32-bit, also
splitable into pairs of 16-bit timers). (The board actually uses a second
TM4C123 chip to handle the interface for programming!). For beginners, TI
cloned the Arduino IDE as Energia. (though for some reason the visit link
under the IDE Help is going to Arduino site -- some programmer missed a URL
I guess).

--
Wulfraed Dennis Lee Bieber AF6VN
wlfraed@ix.netcom.com http://wlfraed.microdiversity.freeddns.org/

On 20-06-2021 17:06, Aoli wrote:
> I bought a Pi4 and now ...
>
> Where can I get the best training on-line to work with the Pi4 hardware
> and learn to code for it too ?
>
> I want to make a remote control vehicle with a camera that I can drive
> around my house.  I am handicapped and do not get around well and just
> would like to see what is going on in other parts of the house.

You won't get your answer here. Go to
https://www.raspberrypi.org/forums/ and choose a topic. Also they have
https://www.raspberrypi.org/forums/viewforum.php?f=102

On Tue, 22 Jun 2021 13:21:08 -0400, Dennis Lee Bieber
<wlfraed@ix.netcom.com> declaimed the following:

> 8 "cogs" (cores) running in lockstep, all sharing the 32 GPIO lines.
>Nominally a core runs Propeller BASIC interpreter which accesses compiled
>code from external memory (there is controller that rotates from cog to cog
>allowing access to external memory), but can be loaded with Propeller
>assembly code. I believe there is also a C compiler available.
>

Too many IDEs <G>

SimpleIDE is the C-based version (there is a command line Propeller GCC
version for the masochists).

Propeller IDE appears to be focused on SPIN, though the help system has
the PropBasic manual listed. SPIN and PropBasic appear quite similar,
though some differences exist. No longer maintained (supposedly, but
someone tweaked the github sources in the last year).

Propeller Tool handles SPIN and Propeller Assembly, appears to be
updated for the new P2 chip (I haven't seen anything obvious in the pages
for the other two IDEs)

Plug-in for Visual Studio Code using a third-party compiler...
(FlexProp). Meant for the P2 chip (though the IDE can be toggled to P1,
don't know how that affects VSC).

--
Wulfraed Dennis Lee Bieber AF6VN
wlfraed@ix.netcom.com http://wlfraed.microdiversity.freeddns.org/

On 22/06/2021 14:53, Martin Gregorie wrote:
> OTOH, if you'd rather go multi-process, then writing a set of co-
> operating processes in C that communicate through a block of shared
> memory and use semaphores to co-ordinate access is fairly easy,
> especially if you have the UNIX Systems Programming book I recommended.
>
No need to go that deep for many apps. My pi runs a multi-process piece
of code that simply uses a file in a small ram disk created for the
purpose.

Obviously in physical terms it is shared memory, but in logical terms
its just a file.

One process deletes it and rewrites it - the other process reads the
data in it.

--
There is something fascinating about science. One gets such wholesale
returns of conjecture out of such a trifling investment of fact.

Mark Twain

Re: Training
By: Aoli to All on Sun Jun 20 2021 08:06 am

> I bought a Pi4 and now ...
>
> Where can I get the best training on-line to work with the Pi4 hardware
> and learn to code for it too ?
>
> I want to make a remote control vehicle with a camera that I can drive
> around my house. I am handicapped and do not get around well and just
> would like to see what is going on in other parts of the house.

There is a relevant Linux Magazine article.

https://www.linux-magazine.com/Issues/2018/215/RaspPi-Controlled-Toy-Sailboat

It is for building a remote control boat that you can maipulate from your
smartphone.

--
gopher://gopher.richardfalken.com/1/richardfalken

On Wed, 23 Jun 2021 06:32:38 +0100, The Natural Philosopher wrote:

> No need to go that deep for many apps. My pi runs a multi-process piece
> of code that simply uses a file in a small ram disk created for the
> purpose.
>
That depends on the volume of stored data. I agree that an in-memory FS
would work for gueuing small data items, but could turn out to be a
bottleneck for handling large data items simply because moving them
between processes and the FS becomes a bottleneck of you're handling lots
of large items.

The ETL case I mentioned was a case in point: the data items were logfiles
from a large network of message switches, each holding several MB of log
records. The network was made of hundreds to thousands of switches, each
writing a new logfile per day. Since the data sanitisation and
reformatting process involved loading each logfile into RAM, passing it
through 8-10 worker processes to convert each logfile to a common format:
the switches were of various makes and models, so their log formats
differed. As each logfile had been converted to the common format it was
passed it to the datawarehouse loader and deleted from RAM. It was
important for system speed that the sanitising and reformatting steps
could run in parallel and that the logfiles were not copied between
workers: consequently each logfile was loaded into RAM and a reference to
it was passed to the logfile storage manager. This owned all the in-
memory logfiles and kept track of the status of each one. Workers were
handed a reference to the next logfile, applied the changes they were
configured to make and then released the logfile, marking it ready for
the next processing stage, which meant that, once a logfile was loaded
into RAM , it stayed at the same physical address until the datawarehouse
loader program added its content to the database and told the logfile
manager to delete it from RAM.

The fact that each logfile occupied the same RAM address from being read
in until it was loaded into the datawarehouse saved a LOT of mill time:
If we'd used an in memory FS instead, each log would have had to be read
into each worker and written back to the FS when that step was complete.
We'd also have lost the ability to tune performance by running multiple
copies of each worker.

> Obviously in physical terms it is shared memory, but in logical terms
> its just a file.
>
Of course, but in the case I described, the mere fact that each logfile
stayed at the same address once it was loaded into RAM and remained there
until it had been loaded into the database and deleted, saved a lot of
CPU cycles compared with reading it in to a worker, applying changes and
then writing it back to the FS would have required.

Also, having a collection of simple processes, each applying a single
operation to a single field type, made system configuration simple and
the ability to run multiple copies of a slow process made system
performance tuning much easier.

--
Martin | martin at
Gregorie | gregorie dot org