Battery ground, RS232

I am thinking the GND may be necessary.

Luhan

You *can* for sure.

Graham

The PC and embedded device are at different potentials ? That might be a problem ! I'd fix that first.

Graham

Pooh Bear =E5=AF=AB=E9=81=93=EF=BC=9A

problem

Hi Graham,

I have connected GND, but still can't work. Always got wrong data, does it possible PC's voltage level can't sutable embedded device's ?

Best regards, Boki.

problem

RS232 supports a range of voltage levels. What's the RS232 interface chip in the embedded device ?

Graham

Pooh Bear =E5=AF=AB=E9=81=93=EF=BC=9A

e a problem

in the

Hi,

Not sure, but my embedded device is 3.3V power supply. Should I do anything to meet PC?

Thank you very much!

Best regards, Boki.

You almost certainly need an RS-232 level shifter, like one of the MAX232 type ICs. RS232 signals coming out of most micros are

*positive* logic swinging between 0 and Vcc, whereas RS-232 requires negative logic with negative swings - + and - 10V is common, but a wide range is supported - +5 to -5 or even +5 to 0 are acceptable to some equipment, though with lower noise and resistance to ground imbalance problems. You can also roll your own level shifters, including stealing the -ve rail from an incoming signal using a diode and capacitor.

Please, no-one bitch about the exact definition of the RS-232 standards. I know there are standards, and that they're widely flouted, and I don't care - I doubt Boki does either.

Clifford Heath =E5=AF=AB=E9=81=93=EF=BC=9A

Hi,

I just check the MAX232 data, the operation speed seems not high enough for my app.

I am using 460.8Kbps ~ 921Kbps app, ( for this I have buy a PCI UART card ...)

Any comment is appreciated!

Best regards, Boki.

problem

the

If the embedded RS232 line driver can only output 3.3V it's no surprise that it doesn't work. You really need to look at the interface chip. Are you using the RX and TX lines on a processor directly by amny chance ?

Graham

Pooh Bear =E5=AF=AB=E9=81=93=EF=BC=9A

ce?

ht be a problem

chip in the

hat it doesn't

and TX lines on

Yes... and now... I found the MAX232 is too slow for my this app..

>

There are literally dozens of alternatives that all need different sized (or no) external capacitors and have different maximum rates. That's why I said "*like* one of the MAX232...". Almost every manufacturer seems to make a variant now - I'm sure you can find one.

Indeed a MAX232 isn't fast enough. Is this what you were using ?

Do you actually need such a fast data rate ?

Graham

Naughty boy !

Try looking at the PCI serial card you have to see what they use.

Graham

Pooh Bear =E5=AF=AB=E9=81=93=EF=BC=9A

I am sending jpg files. As faster as better.

I guess USB maybe better, but in order to meet Bluetooth SPP...

Best regards, Boki.

problem

"Getting Wrong Data" sounds like a baud rate mismatch.

Good Luck! Rich

problem

Thanks, but that case...

Confusing, there is no ADM3202 near my place... any replacement? :D

Boki.

Plenty. Check that Google link I sent you. Intersil for example.

Graham

Common problems connecting a PC to an embedded device:

1. Yes, you usually need the ground wire, unless you are running the PC on the same power supply as the embedded device, in which case you already have a ground wire coming in a different way.
2. If this is a laptop and you are out in the field, unplug the car charger from the laptop. The inverters used can create nasty ground loops that mess up communications and in rare occasions can blow up the serial port on your embedded device.
3. Ensure you are running the correct software on your PC, that knows the protocol to talk to the embedded device. Is your device talking Modbus, AT modem commands, some proprietary protocol, etc?
4. Ensure no other software is running on the PC which might be using the serial port. In general, only one program can use the serial port at a time.
5. Ensure that the port settings match in the PC software and the embedded device. Baud rate, parity, stop bits, etc. are important.
6. Some devices are expecting hardware handshaking on the serial port. If this is the case, you either need to disable hardware handshaking, or else hook up the extra pins needed on the serial port (RTS/CTS, DTR/DSR, etc.) as well as just RX, TX, and GND.

Hope this helps!

Tim Kirk snipped-for-privacy@rogue-engr.com Rogue Engineering Inc

Boki wrote: