IO source/sink specs

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>from the help line
>I just received 3 of your ARMmite computers and need to know what the current
sourcing spec is. I see in the general specs that you list a sourcing current
max of 4 mA. That would generally be different than the current sinking spec.
How many mA can it source on the pins?

The ARMmite uses an LPC2103, and the spec for this is linked in the Help Files :
Hardware Section : CPU Details

The source and sink currents are 4 mA. The 2 currents are normally the same in
modern CMOS devices.

We don't duplicate the NXP specs in our helpfiles, as those specs are updated by
NXP from time to time.

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Thanks bruce@basicnode and peterjtait for their insight . You guys make this
stuff look easy . I did come up with a convoluted way to do a decimal / binary
conversion ; lotsa code though .

-------------------------

Bruce brought up a "clarity issue" with my circuit explanation . Right on Bruce
. Perhaps a simple pin assignment below would help . These are the signals that
my project uses at its interface to the "buffered" I/O signals of the ARMite . (
via 74LS244's)

I/O 0 becomes DATA 0 on the project side ( output direction only )
I/O 1 becomes DATA 1
.... thru to
I/O 7 becomes DATA 7

I/O 8 thru I/O 11 become the LSB (A,B,C,D bits) of an ADDRESS used by a 74154
4x16 Multiplexer .

I/O 12 "gates" the above multiplexer and thus selects any of 16 ports
of the project having been addressed by I/O pins 8 thru 11 above .

I/O 13 is used as an OutputEnable signal to "latch" I/O data lines to some 7
segment displays . These displays are routed thru some 74573 Octal D flips . The
OutputEnable holds the previous data on the bus into the display via the 573's.

The OVERALL idea : Set up an 8 bit data word , use the multiplexer as a "chip
select" via the 74154 to select an output device , and then
latch the data into the output device via the OutputEnable and the 74573's.
(latches data to HOLD into device . NO REFRESHING needed)

OUT(0)=x thru OUT(7)=x (8 bit data)
OUT(8)=x thru OUT(11)=x (chip select address of 74154 MUX)
OUT(12)=0 (GATE enable 74154 MUX with selected address)
OUT(13)=0 (latch up the data into displays and HOLD)
OUT(12)=1 (reset chip select (active low))
OUT(13)=1 (reset OutputEnable (active low))

As Peter alluded to , I'll recheck my wiring yet again .
This stuff is the most fun that I have had since the kids moved out !

Keep On Truckin' and don't give up : EVER . Regards to all;

Rick

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Thanks guys for the recent advice regarding my hardware problem . As Chris
explained , trying to select an " active lo " logic signal with an " active hi "
will not make things work very well .

I had not made that mistake in over 20 years . I guess that I am a ROOKIE again
. Can't beleive that I made that faux pas !

I'm still tearing out some hair trying to come up with a routine to do decimal
to BCD conversions . I'm trying to drive pairs of 7447 BCD / 7 segment decoders
from an 8 bit data bus assigned by I/O 0 thru I/O 7 ARMite pins .

Thanks again to Bruce for suggesting the MOD command . It makes for a good root
base for this routine .

--------------------------------------------------------------------

A buddy of mine works at an electronics recycling center where I get to go thru
the bins to salvage parts from . I end up with a lot of stepper motors from
printers and such . My question is : If I set up a group of 4 "constants" to
drive the phases of one of these motors , is there an easy way to do an old
style INDIRECT ADDRESSING , look-up
table kinda thing to keep track of the motor's current phase step ?

Regards to ALL . Thanks again for the help ! Remember , DON't give up.

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Gentlemen : This saying IS my credo . As a kid from the proverbial "stix" in
Canada , I grad from a local college majoring in electronic engineering tech.
with minors in applied physics and calculus . Hated the calc ; loved the physics
! All that was 1983 .

Worked for a subsidiary of Litton Resources Systems LRS (Houston) of which I
generated some 5 patents in 4 years , some of which applied to your PATRIOT ABM
system . Guidance actally . I wish that I had the ARMite at that time ! I had to
do a " look up table " in EEPROM to solve some ballistic stepper motor response
. All DECLASSIFIED in 1993 .
Don't worry none .

I just wanted to say THANX to all you guys who respond to my "simple sounding"
queries . As I've always said ; I'm a HARDWARE guy ! If this stuff was in 8080
or 6502 , I could handle it alright .

Hardware is EASY . Firmware ....?

Anyway ; DON'T EVER GIVE UP on the project that you are working on !
Something will come out of it ; good results OR bad . Learn from ALL of them !
Please keep telling me what I'm doing wrong . How else can I catch up to you
guys ?

Anybody HIRING guys who think "outside of" the box ?

Appreciate ALL of your guys' efforts . Don't give up .

Rick (Prompted by a neighbor kid who wants to LEARN)

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--- In ARMexpress@yahoogroups.com, "chernenkoffr" wrote:

> Anyway ; DON'T EVER GIVE UP on the project that you are working on !
> Something will come out of it ; good results OR bad . Learn from ALL of them !

Well said! My personal theme song is 'Don't Give Up' by Peter Gabriel:

http://www.petergabriel.com/discography ... _the_Tree/

Cheers,
Chris

Chris Burrows
CFB Software
Armaide v2.1: LPC2xxx Oberon-07 Development System
http://www.armaide.com

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Gentlemen :

As I have a neighborhood kid who is a kind of "student" , he asked a couple of
POINTED questions today as we were going over the finer details of using an
oscilloscope . The lad asks : " What is a mSec ? What is a uSec ? " . We turned
off the scope and had a small discussion .

Having found out that the young lad was in grade 10 ( A "Junior" in USA schools
) , he was casually employed as a carpenter in his "off hours" . Knowing that he
knew how to use a measuring tape , accurate to 3 decimal places at best estimate
; I tried to impart the idea that the electronic industry tends to use 12
decimal places in its calculations as a minimum ; and sometimes 15 decimal
places .

The lad ponders this fact . His retort : " Jim asked me to trim off a 2 by 4
by a BCH . What's up with that ? I didn't know what he meant ".
As I am a plumber / gas fitter as well as an electronic engineer , I eventually
figured out what he was confused with .

In Canada , we are taught to use both Imperial and S.I. ( Metric ) units of
measure as a matter of fact . Fluency in both systems tends to guarentee an
understanding that is universal . The older "trades oriented" measuring system
was the one that he was being confused by : The "C HAIR" measuring system .
This system's units are not based upon Angstroms , Nanometers , Millimeters ,
nor Centimeters ; but upon color !

At best , the C HAIR is becoming rare indeed . If one tends to find one , one
would find that the "Red Head" variety is far thicker than either the standard
"Brunette" ones or the ; finest of them all , the "Blonde" ones .

I decided to leave the lad with the advice that IF he should ever discern which
type was more accurate for general measuring , he should relay to me the
"accuracy" as to decimal placing . I think that it is 3 myself .

I thought that this one was kinda funny . Forgive me if I offend anyone .

DON't Give Up !

Rick

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>from help line
>about how to interface to a hall effect sensor. With the hall effect sensor I
want to set an IO pin to high, output low voltage to the sensor, and monitor the
return on an adc channel, determining when a magnet passes the hall effect
sensor. will I need to put a resistor on this wire to prevent over current or is
the output current on the pins self limiting?

The IOs have no current limiting so you can burn them out if you short them out
for long periods or try to pull too much current out of them

>With the HWPWM, im currently going to send the 10 mA 3.3V signal to a 12V
preamp, and use the ~100 mA square wave to switch the power transistors,
controlling 120V DC at 5 amps at 50% PWM...does that seem feasible?

The IOs can drive Darlington transistors, depends on the type. With 5A you
probably want to use a MOSFET otherwise you'll be dissipating a lot of power in
power transistor and it would require a lot of heat sinks.

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Do you think it is possible to use a darlington to control 1-5 amps (at
120VDC)directly with the IO? If so please inform as to the chip capable of doing
this. We can probably pay you for a more in depth consultation on this
application. I have some darlington mosfets that may be suitable (IRF630) gain =
500, 10A, 200V. im pretty reluctant to get the IC anywhere near 120V. Thinking
of using an optocouple.
Justin

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>I have a 5v relay that is a SANYOU SRD-S-105D. I was wondering what type of
transistor I should use to buff the 3.3v to the 5v I need to power this relay.

Except for small reed relays, you will need to buffer the drive for a relay.

I couldn't find a spec sheet on the relay you mention, so I looked at Digikey
website and sampled some Omron 5V relays, which have coil currents of 24- 240 mA

At the low end a simple 2N3904 and diode would be adequate.

For the bigger relays a MOSFET would be needed.

Back of the envelope calculation

assume 1V saturation voltage of transistor, would be upto 1/4 watt in the
transistor (which with a big heatsink the 3904 might do it, but I'd step up to a
bigger device).

Details on these circuits on page 248 of Claus's book we link to on the support
page

http://www.ckuehnel.ch/PDF/bs2pCommnFeat.pdf

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Hi Folks,

I'm new to the Armmite Pro and this forum, and I did do a quick search before
posting, but does anyone know if the Armmite Pro can Source or Sink on Output?
I'd like to "drive" a PNP transistor using HWPWM.

Thanks much, Mike