serial port pinout on 50gs
cyrille de Brebisson
just as an info, because I was asked for the info by a couple of peoples,
the pinout for the serial port on the 50gs is, from right to left, when
looking at the top of the calcualtor: GND, RX, TX and VBat (battery
voltage).
cyrille
James M. Prange
Thanks for that information.
Much more important to me is what voltage can the 50g's RX pin
withstand. Can it use a +5V signal level? Perhaps a bit more?
--
Regards,
James
Avatar_e
but my new pc does not has serial port :-( only has massive usb ports
everywhere
Chips
reads serial through a usb port. They work pretty well. I use one my Sokkia
surveying instrument.
GC
"Avatar_e" <erwi...@gmail.com> wrote in message
news:1156790322.7...@i3g2000cwc.googlegroups.com...
Johannes Thordarson
I don't know if this is relevant, but I put it here anyway.
http://www.educalc.net/2146080.page
http://www.educalc.net/2147084.page
Johannes
On Tue, 29 Aug 2006 02:01:51 GMT, "Chips" <Chi...@reliableins.nospam>
wrote:
cyrille de Brebisson
that, I do not know, you will have to dig through the samsung arm9 docos...
cyrille
"James M. Prange" <jmpr...@i-is.com> wrote in message
news:cff4c$44f32fb9$4267ebd0$28...@123.NET...
James M. Prange
cyrille de Brebisson wrote:
> hello,
>
> that, I do not know, you will have to dig through the samsung arm9 docos...
Okay, fair enough.
In the Samsung document, under
ELECTRICAL DATA
ABSOLUTE MAXIMUM RATINGS
I find:
Parameter | Symbol | Rating | Unit
DC Input Voltage | VIN | 3.3V Input buffer | 3.8 | V
| | 3.3V Interface / 5V Tolerant input buffer | 6.5 |
I'm hoping that the UARTs' RX lines would be classified as
"3.3V Interface / 5V Tolerant input buffer".
But in a different thread, you wrote: "they are protected by a
Zener, but only to a certain level, so be carefull...", so I guess
that, as long as the voltage is something "reasonable" and a
current limiting resistor is used, a typical 3.3V/RS-232
transceiver should be okay.
If you (or anyone else) happen to know the Zener's characteristic
voltage, that may be of interest.
Antti Louko
> Parameter | Symbol | Rating | Unit
> DC Input Voltage | VIN | 3.3V Input buffer | 3.8 | V
> I'm hoping that the UARTs' RX lines would be classified as
> "3.3V Interface / 5V Tolerant input buffer".
> But in a different thread, you wrote: "they are protected by a
> Zener, but only to a certain level, so be carefull...", so I guess
> that, as long as the voltage is something "reasonable" and a
> current limiting resistor is used, a typical 3.3V/RS-232
> transceiver should be okay.
> If you (or anyone else) happen to know the Zener's characteristic
> voltage, that may be of interest.
It should be easy enough to measure the Zener voltage by applying
eg. 9V through a 500kOhm resistor and measure the voltage over the
input pin. Smaller resistance should work but 500k is on the safer
side. I would do this myself but I don't have a 50g.
If you don't understand what I am suggesting, please don't try. I
take no responsibility of possible damage!
James M. Prange
> Hi,
>
> I don't know if this is relevant, but I put it here anyway.
>
> http://www.educalc.net/2146080.page
> http://www.educalc.net/2147084.page
Yes, those are certainly relevant, particularly that first link.
I suggest that it would be better to use a lower-power chip, such
as something from the ICL3221 or MAX3221 families, instead of a
MAX232 or MAX232A. Links to the manufacturers' information:
http://www.intersil.com/data/fn/fn4805.pdf#search=%22ICL3221%22
http://www.maxim-ic.com/quick_view2.cfm/qv_pk/1069
On the Museum Forum, Tim Wessman posted a link to converter cables
complete with the DB9 connector; you'd have to add any voltage
regulation needed and the connector for the 50g yourself. See:
http://www.superdroidrobots.com/shop/category.asp?catid=41
Also this one, which seems to be the converter circuit assembled
on a printed circuit board only:
http://www.tildesign.nl/rs232_ttl_converter-20107101P2N
A possible problem is that converter chips are typically designed
to be used with a Vcc up to 5.5V, with an absolute maximum of 6V,
and with 4 fresh alkaline cells, the +VBat from the 50g may be a
bit over that. One solution would be to use a diode (or maybe even
two) in series with Vcc to drop the voltage to something
acceptable. Another would be use a current-limiting resistor in
series with Vcc and connect a Zener between Vcc and ground. One
could always use a DC to DC voltage converter, but that seems to
me to be a bit of "overkill". Of course, if you use NiMH cells,
this won't be a problem.
> Johannes
>
> On Tue, 29 Aug 2006 02:01:51 GMT, "Chips" <Chi...@reliableins.nospam>
> wrote:
>
>> You can do a web search and get a usb-serial adapter. It has software that
>> reads serial through a usb port. They work pretty well. I use one my Sokkia
>> surveying instrument.
>>
>> GC
>>
>>
>> "Avatar_e" <erwi...@gmail.com> wrote in message
>> news:1156790322.7...@i3g2000cwc.googlegroups.com...
>>> Thanks for the info... i will try to do my own cable :-D
>>>
>>> but my new pc does not has serial port :-( only has massive usb ports
>>> everywhere
--
Regards,
James
James M. Prange
I agree, but I don't have a 50g either.
--
Regards,
James
TW
> complete with the DB9 connector; you'd have to add any voltage
> regulation needed and the connector for the 50g yourself. See:
> http://www.superdroidrobots.com/shop/category.asp?catid=41
I don't think those will work anymore. That was posted before I found
out that the signal is inverted.
TW
Colin Croft
You may find this useful - a guide to installing a USB/Serial converter.
It's sometimes not simple. It's written for the 39G but the info should
still be relevant.
http://www.hphomeview.com/Tips/USB%20to%20Serial%20Converters.pdf
James M. Prange
Thanks for the heads-up Tim, but now I'm confused again (or maybe
I should say "still").
My understanding is that, conventionally, the data signals at a
UART's serial connections (before being shifted to EIA-232 levels)
are near 0V for 0 bits, and some positive voltage (+3.3V in the
case of the 50g) for 1 bits.
EIA-232 transmitted levels are +5V to +15V for 0 bits, and -15V to
-5V for 1 bits, and for receiving the ranges are +3 to +15V for 0
bits, and -15V to -3V for 1 bits.
So if I've got that right, a typical "level-shifter" (or
"converter", "translator", or whatever) inverts the signals as
well as shifting them between unipolar and bipolar signals and
changing the amplitudes.
Are you saying that those cables are designed to be used with a
UART with "inverted" serial signals, that is, near 0V for a 1 bit
and positive for a 0 bit?
--
Regards,
James
TW
> UART with "inverted" serial signals, that is, near 0V for a 1 bit
> and positive for a 0 bit?
I don't think they are designed to invert the signal as well as change
the voltage higher. You did understand what I was saying: the signals
coming out of the port use 0V for a 1 bit and +3.3 for a 0.
TW
James M. Prange
You're saying that the signal at the serial port of a *50g* is 0V
for a 1 bit and 3.3V for a 0 bit?
If so, that seems to rather throw a monkey wrench in the works.
All of the converters that I'm aware of include inverting the
polarity (although there may well be some that don't that I'm just
not aware of).
So to use an inverting converter with the 50g, we have to have an
inverter (actually, a pair, but I have in mind a chip with at
least two inverters in the package) between the 50g's serial port
and the level-shifter?
--
Regards,
James