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34s flashing cable possible candidate?
06-23-2014, 11:25 PM
Post: #1
34s flashing cable possible candidate?
I found the following cable in a box. I have to confess I can't remember what it was used for but I would suspect it was my old HP Jornada cable though it is written "Belkin" on the USB plug. This cable looks pretty similar to the official 30s flash cable doesn't it?

I couldn't figure out how to open the small box in the middle of the cable, it looks sealed. There is a two positions button in the middle that lits a red or green led.
I would like to reuse this cable to flash the 30s into a 34s but I'm not sure how to proceed from there... Any idea?

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06-24-2014, 08:08 AM
Post: #2
RE: 34s flashing cable possible candidate?
If it was mine, I would cut the plug, take a multimeter (or even better, a oscilloscope) and do some checks. The serial interface works at TTL level, and the signals should swing betwwen 0Volt and 3.3Volt.

But before doing so, I would plug the USB side to a PC and see if it is recognized as a serial COMxx port, otherwise it is no good for what we need.

Jose Mesquita
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06-24-2014, 08:53 AM (This post was last modified: 06-24-2014 09:14 AM by pito.)
Post: #3
RE: 34s flashing cable possible candidate?
(06-24-2014 08:08 AM)jebem Wrote:  But before doing so, I would plug the USB side to a PC and see if it is recognized as a serial COMxx port, otherwise it is no good for what we need.
There are 2 kinds of "usb" data cables for mobile phones on the market:
1. straight usb cables - they pass through the usb signal directly to the mobile
2. cables with usb/serial converter inside - they include the chip, need a sw driver usually and show as ComX in the device manager then.
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06-24-2014, 09:49 AM (This post was last modified: 06-24-2014 10:04 AM by Tugdual.)
Post: #4
RE: 34s flashing cable possible candidate?
Thanks for your kind reply. I agree that an oscilloscope would be the absolute answer to my questions but I have none :-(.
One more thing that came in my mind is that this cable is probably quite old. Like 7 years old minimum. Do you know if the expect thecnology was already in place by this time?
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06-24-2014, 12:59 PM (This post was last modified: 06-24-2014 01:00 PM by pito.)
Post: #5
RE: 34s flashing cable possible candidate?
(06-24-2014 09:49 AM)Tugdual Wrote:  One more thing that came in my mind is that this cable is probably quite old. Like 7 years old minimum. Do you know if the expect thecnology was already in place by this time?
The cables (ie. CA-42, DKU-5) are 10-12y old stuff..
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06-25-2014, 11:14 PM
Post: #6
RE: 34s flashing cable possible candidate?
(06-24-2014 08:08 AM)jebem Wrote:  The serial interface works at TTL level, and the signals should swing betwwen 0Volt and 3.3Volt.

You need to make sure to test the voltage levels, as there are also 5V and 1.8V TTL serial interfaces in use also. An older cable may be more likely to be a 5V version, which would damage anything using a lower voltage I/O.
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06-25-2014, 11:40 PM (This post was last modified: 06-26-2014 12:12 AM by Dave Frederickson.)
Post: #7
RE: 34s flashing cable possible candidate?
(06-25-2014 11:14 PM)cruff Wrote:  An older cable may be more likely to be a 5V version, which would damage anything using a lower voltage I/O.

Not necessarily true. Many devices have Low-Voltage TTL logic level pins, yet are 5V tolerant. From the Atmel datasheet:

Voltage on Input Pins
with Respect to Ground...... ..............................-0.3V to + 5.5V

So any circuitry (level-shifters) to ensure that the TTL signals are 3V is a waste.

Dave
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06-26-2014, 11:35 PM
Post: #8
RE: 34s flashing cable possible candidate?
(06-25-2014 11:40 PM)Dave Frederickson Wrote:  Not necessarily true. Many devices have Low-Voltage TTL logic level pins, yet are 5V tolerant.

True, but you really need to review the data sheet to make sure you won't kill something!
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06-27-2014, 12:14 AM (This post was last modified: 06-27-2014 12:24 AM by Dave Frederickson.)
Post: #9
RE: 34s flashing cable possible candidate?
(06-26-2014 11:35 PM)cruff Wrote:  
(06-25-2014 11:40 PM)Dave Frederickson Wrote:  Not necessarily true. Many devices have Low-Voltage TTL logic level pins, yet are 5V tolerant.

True, but you really need to review the data sheet to make sure you won't kill something!

Perhaps you didn't read all of my post. I not only reviewed the datasheet, I quoted from it.
To summarize, the input pin on the ARM serial interface is 5V-tolerant. Connecting a USB-Serial adapter that uses 5V TTL logic will not cause any damage.

Dave
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06-27-2014, 03:01 AM
Post: #10
RE: 34s flashing cable possible candidate?
The official standard for RS-232 requires voltage levels that go both above and below ground.
Some go as high as +- 10Volts. If the cable is designed to talk to serial port, it may generate these
high positive and negative voltages. So just because the Atmel processor in the HP-30B is 5Volt tolerant does not mean that you can just attach anything to it. It would be prudent to at least measure the cable's output pins with a volt meter to be sure it does not generate high positive or negative voltages.
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06-27-2014, 06:51 AM
Post: #11
RE: 34s flashing cable possible candidate?
(06-27-2014 03:01 AM)BarryMead Wrote:  The official standard for RS-232 requires voltage levels that go both above and below ground.
...

Even if you clip the voltages, a regular RS232 signal wouldn't work because the levels are inverted from the TTL signals.

I've build my own cables from an FTDI USB/TTL 3.3V "cable". The converter sits in the USB plug, the other end is an open cable.

Marcus von Cube
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06-27-2014, 07:26 AM (This post was last modified: 06-27-2014 07:28 AM by BarryMead.)
Post: #12
RE: 34s flashing cable possible candidate?
(06-27-2014 06:51 AM)Marcus von Cube Wrote:  Even if you clip the voltages, a regular RS232 signal wouldn't work because the levels are inverted from the TTL signals.
Marcus is right. If the other end of the cable looks like a 9-Pin D connector, there is no hope that
it will provide the signal polarity or voltages you want to program the calculator. Even though it
"LOOKS" like the programming cable physically, electrically it isn't even close.
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