Mecrisp on the TI Stellaris Launchpad

On 4/17/2015 4:15 PM, mm0fmf wrote:
> On 17/04/2015 19:47, rickman wrote:
>> On 4/17/2015 12:56 AM, Paul Rubin wrote:
>>> rickman <gnuarm@gmail.com> writes:
>>>> I was using a gadget to measure the voltage and current going into the
>>>> rPi.  That side is at 5.25 volts give or take with around 400 mA of
>>>> current.  I moved the meter to the launchpad and the output on the USB
>>>> port is only 4.95 volts.
>>>
>>> I remember reading somewhere (probably adafruit.com) that you should use
>>> a pretty beefy 5V power supply with the rpi especially if it's under any
>>> type of load.  They actually tweak their rpi power supplies to deliver
>>> 5.25 volts to compensate for some inevitable sag.
>>>
>>> I don't remember hearing that the USB ports themselves are out of spec
>>> but it's possible.  Despite popular misconception USB ports are only
>>> supposed to be able to deliver 100 mA unless they grant the client
>>> "permission" to draw more (up to 500ma), through a power negotiation
>>> protocol that's part of USB.  Most x86 motherboards can deliver 500 mA
>>> with no problem, so lots of badly designed client devices just assume
>>> the power is available, and try to draw it without bothering with the
>>> protocol.  Maybe something like that is going on here.
>>
>> I'm not 100% certain of this, but I believe the rPi runs input power
>> through a Polyfuse which does have some noticeable resistance and so
>> voltage droop.  I've cross-posted this to the rPi group to see if anyone
>> will confirm it.
>>
>
> When in doubt check the spec... USB2.0 ports are 5v +/- 5% so 4.75V to
> 5.25V between the pins on the connector.
>
> 4.95 is almost perfectly in the middle.

I never said that measurement was out of spec.  I was commenting on the 
facts that there is a quarter volt lost across the rPi and that the 
launchpad seems to reset when I type on the USB keyboard.  Maybe it's 
not voltage related, but the quarter volt drop is unexpected and there 
are plenty of cases where even an older mouse, like the one I have, 
can't be powered through the rPi.

-- 

Rick

Am 17.04.2015 um 16:42 schrieb Anton Ertl:
> Blajrs Jrolrsen <boegre@no.com> writes:
>> On 2015-04-17, rickman <gnuarm@gmail.com> wrote:
>>> Yes, I figured that out.  It seems the current working directory is not
>>> considered under Linux for finding executables... really!?

Yes, really.

> I think it has something to do with more usage of Unix/Linux by
> non-programmers (to such an extent that they don't even write their
> own shell scripts).

I don't think that argument works.

There have been platforms where a very large fraction of users never 
wrote a program of their own.  The biggest of those has to be Microsoft 
Windows, closely followed by MacOS.

But Unix never was anywhere near the top of that category.  I'm not 
aware of any system that encouraged users to write their own programs 
more strongly than Unix did: the whole "toolkit" paradigm almost forced 
_users_ to become programmers, at least at the shell script level.  And 
how many other systems did come with a bona-fide HLL compiler right 
there in the box?

> In the old times, we had "." first in the PATH.  If I am working on a
> new version of Gforth, and am in the build directory of Gforth, then
> saying "gforth" gives me the development version, not the installed
> version.

And that was baskk-ackward.  If only because it's a whole lot easier to
and type the "./" prefix for the exceptional case of wanting something
else than the normal instance of a command, than it would be to figure
out where the "official" one might be, and type the full path to there 
every time you want to be sure you get that.

The distinction between "gforth" and "./gforth" is way easier to handle 
than the one between "/opt/swserver/Forth/GForth/V5/patch1/bin/gforth" 
and "gforth".

> That disadvantage was worked around by removing the "." from the front
> and putting it on the back of the PATH.

That workaround would be half-assed at best, because it relies on the 
obviously flawed assumption that user will never mis-type commands.  But 
because they do, it's relatively easy for an attacker to pre-load their 
traps with lots of mis-typed versions of, 'ls', 'cd', etc.

One other rather important aspect is that the way Unix does it actually
leaves you a _choice_ how you want this handled: _you_ define your $PATH
setting, so you can put '.' in there exactly where you want or need it,
or not at all. On Microsoft platforms, you have no control over it: the 
system forces an implied '.' to the front of your PATH, whether you want 
it or not.

On 4/17/2015 6:25 PM, Hans-Bernhard Br�ker wrote:
> Am 17.04.2015 um 16:42 schrieb Anton Ertl:
>> Blajrs Jrolrsen <boegre@no.com> writes:
>>> On 2015-04-17, rickman <gnuarm@gmail.com> wrote:
>>>> Yes, I figured that out.  It seems the current working directory is not
>>>> considered under Linux for finding executables... really!?
>
> Yes, really.
>
>> I think it has something to do with more usage of Unix/Linux by
>> non-programmers (to such an extent that they don't even write their
>> own shell scripts).
>
> I don't think that argument works.
>
> There have been platforms where a very large fraction of users never
> wrote a program of their own.  The biggest of those has to be Microsoft
> Windows, closely followed by MacOS.
>
> But Unix never was anywhere near the top of that category.  I'm not
> aware of any system that encouraged users to write their own programs
> more strongly than Unix did: the whole "toolkit" paradigm almost forced
> _users_ to become programmers, at least at the shell script level.  And
> how many other systems did come with a bona-fide HLL compiler right
> there in the box?
>
>> In the old times, we had "." first in the PATH.  If I am working on a
>> new version of Gforth, and am in the build directory of Gforth, then
>> saying "gforth" gives me the development version, not the installed
>> version.
>
> And that was baskk-ackward.  If only because it's a whole lot easier to
> and type the "./" prefix for the exceptional case of wanting something
> else than the normal instance of a command, than it would be to figure
> out where the "official" one might be, and type the full path to there
> every time you want to be sure you get that.
>
> The distinction between "gforth" and "./gforth" is way easier to handle
> than the one between "/opt/swserver/Forth/GForth/V5/patch1/bin/gforth"
> and "gforth".
>
>> That disadvantage was worked around by removing the "." from the front
>> and putting it on the back of the PATH.
>
> That workaround would be half-assed at best, because it relies on the
> obviously flawed assumption that user will never mis-type commands.  But
> because they do, it's relatively easy for an attacker to pre-load their
> traps with lots of mis-typed versions of, 'ls', 'cd', etc.
>
> One other rather important aspect is that the way Unix does it actually
> leaves you a _choice_ how you want this handled: _you_ define your $PATH
> setting, so you can put '.' in there exactly where you want or need it,
> or not at all. On Microsoft platforms, you have no control over it: the
> system forces an implied '.' to the front of your PATH, whether you want
> it or not.

I don't wish to insult anyone.  But I will say that I have tried to 
learn linux several times and found poor support from the linux 
community.  Mostly I think there is an attitude that "we" (the linux 
community) got it *right*, when there are many, many more PC users, even 
professional programmers, than there are working under Linux.

Ok, everyone is entitled to their opinion.  But the problem arises when 
it is not understood that this is an opinion, not a universal truth. 
There are good and bad things about both linux and windows.  I would 
like to learn about linux now, so I won't ask "why" anymore.  I'll just 
accept the things that are goofy about it just as I have done with 
windows for many years.

-- 

Rick

rickman <gnuarm@gmail.com> writes:
> Mostly I think there is an attitude that "we" (the linux
> community) got it *right*, when there are many, many more PC users,
> even professional programmers, than there are working under Linux.

Linux has its roots in Unix which goes back to the 1970's, long before
the existence of PC's, so it tends to use old-school approaches:

http://2ndscale.com/rtomayko/2006/that-dilbert-cartoon

Now I am a bit stuck trying to get a serial port terminal emulation 
running.  It would appear that miniterm is the right program to use, but 
while dealing with the slowness of the rPi when web browsing I have yet 
to find it exactly.  I thought I had found it at a site called Py 
Serial.  But I think what I downloaded with some sort of python wrapper 
for miniterm.  I'm not sure really.

Even once I get a terminal emulator running, I'm not sure how to find 
the ID of the device I'll be talking to with it.  It is a TI launchpad 
with a USB emulated UART.  These things are like falling off a rock in 
the PC world... mainly because I've come up the learning curve and know 
it.  Will miniterm have the smarts to find the one serial port on the 
machine or do I have to figure out the ID of this USB serial port and 
tell it?

-- 

Rick

rickman <gnuarm@gmail.com> writes:
> know it.  Will miniterm have the smarts to find the one serial port on
> the machine or do I have to figure out the ID of this USB serial port
> and tell it?

Do "ls /dev/tty*" and it should give you a list of possible devices
where the port is.  

Do you use irc?  You can probably get quicker help on the #raspberrypi
Freenode channel.

On 4/17/2015 8:14 PM, Paul Rubin wrote:
> rickman <gnuarm@gmail.com> writes:
>> Mostly I think there is an attitude that "we" (the linux
>> community) got it *right*, when there are many, many more PC users,
>> even professional programmers, than there are working under Linux.
>
> Linux has its roots in Unix which goes back to the 1970's, long before
> the existence of PC's, so it tends to use old-school approaches:
>
> http://2ndscale.com/rtomayko/2006/that-dilbert-cartoon

I'm going to get the better computer, but it costs $35.  The rPi 2... 
This thing is not much of a desktop.  I have a 10 year old machine that 
runs XP and does rings around the rPi.  But then it has it's own table, 
burns enough power to warm a cat very nicely while the rPi serves as a 
night light and sits on top of my monitor... lol

-- 

Rick

rickman <gnuarm@gmail.com> writes:
> I'm going to get the better computer, but it costs $35.  The rPi
> 2... This thing is not much of a desktop.  I have a 10 year old
> machine that runs XP and does rings around the rPi.  

The Rpi is an embedded linux board that I hope is not being sold as a
desktop.  The Rpi2 has four cores each around 1.5x the speed of the
Rpi1, and I don't know if the parallelism will really help with web
browsing.  I can understand not wanting to lug a full sized laptop
around but there are some very nice, fast ultralights around these days.
I want one of these:

http://www.dell.com/us/business/p/xps-13-linux/pd.aspx

Ironically one of the easiest places to go look at one in person is the
Microsoft store.  But I'd buy the Linux version above.

On 4/17/2015 8:24 PM, Paul Rubin wrote:
> rickman <gnuarm@gmail.com> writes:
>> know it.  Will miniterm have the smarts to find the one serial port on
>> the machine or do I have to figure out the ID of this USB serial port
>> and tell it?
>
> Do "ls /dev/tty*" and it should give you a list of possible devices
> where the port is.

That gives me a list of tty, tty0 through tty63, ttyAMA0 and ttyprintk. 
  The list is the same if the device is plugged in or not.  Of course, I 
don't know for sure what the board should do, but my understanding is 
one port is for use as a debugger and this port is for use as a UART 
interface to the target MCU.  I had found a web page where they were 
developing on this target under Linux.  I'll go back to that to look for 
info.  But I think it was more debugger oriented.

Trouble is most of these pages are from experienced users and they have 
long ago forgotten all the small stumbling blocks to getting started.


> Do you use irc?  You can probably get quicker help on the #raspberrypi
> Freenode channel.

I'm not familiar with irc.  I think I tried it once a long time ago and 
didn't get much traction with it.  I'm expecting there should be 
knowledgeable people in the rPi group.

One of my problems is there really isn't room for the pi, the laptop and 
all the other misc stuff on my work table at the moment.  Maybe I need 
to just work remotely from the laptop.  That would solve my lack of a 
USB hub as well.  I have to unplug the mouse to plug in the launchpad.

-- 

Rick

On 4/17/2015 8:32 PM, Paul Rubin wrote:
> rickman <gnuarm@gmail.com> writes:
>> I'm going to get the better computer, but it costs $35.  The rPi
>> 2... This thing is not much of a desktop.  I have a 10 year old
>> machine that runs XP and does rings around the rPi.
>
> The Rpi is an embedded linux board that I hope is not being sold as a
> desktop.  The Rpi2 has four cores each around 1.5x the speed of the
> Rpi1, and I don't know if the parallelism will really help with web
> browsing.  I can understand not wanting to lug a full sized laptop
> around but there are some very nice, fast ultralights around these days.
> I want one of these:
>
> http://www.dell.com/us/business/p/xps-13-linux/pd.aspx
>
> Ironically one of the easiest places to go look at one in person is the
> Microsoft store.  But I'd buy the Linux version above.

My problem isn't the size of the laptop exactly.  It is the smallness of 
the space available, lol.  I can't use such small machines really.  In 
fact one of my complaints of this 17" laptop is they didn't use all the 
space available for the keyboard so there is no space between the key 
sections.  It is impossible to feel for any keys like the arrows or the 
Home, End, PgUp, PgDn keys.  You have to look every time you reach for 
one.   Then the rPi is tiny, but the 19" monitor is not and the compact 
Dell keyboard is wider than the 17" laptop, along with all the tools, 
drawers, lamps, outlet strips and misc junk on the relatively small 
table top.  If I put the laptop where the keyboard is I have to lay the 
keyboard behind it... I could bring another table in just for the 
laptop.  Or I could admit I am never going to fire up the XP computer 
again and use that tray.

But for the short term, I'm just looking for a way to talk to the 
launchpad from the rPi.

-- 

Rick