Rs-232 Devices Connecting


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lyssdod

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Aug 12, 2010
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Hello guyz, is there a way to connect a rs-232 device (56k dialup modem) to pandora through ext port?

In fact, i'm watching at this cutie and tears are flowing from my eyes:
page2-Half-InchModem1C.jpg

it's the ultimate micro 56k modem from radicom, the link is here. i know it sounds strange, but just imagine if this modem would be integrated into pandora ..... :rolleyes:
 
Yes, use a USB to RS232 adapter. The RS232 device needs to have Linux drivers for you to have any chanced of using it.
 
It's possible (dunno if the kernel is configured to set those up as ttys or not), but why would you want to?
 
Its possible, as there is RS232 on the EXT output connector, but you'd have to disable the kernel console on it before it'd be useful. Easy enough to do, just be aware if you do try to hook things up, there's already something using the port (kernel messages..)
 
A USB adapter would be easiest for actual RS-232. Yes, there are two UARTs accessible from the EXT port but these are 1.8V and therefore require level shifting for RS-232 (e.g. a MAX232 or whatever applicable low power version thereof).

That tiny modem however doesn't even take RS-232 but a TTL signal, so you'd need to level shift 1.8V (or RS-232 from the USB adapter) to TTL. It also requires a 3.3V (nominal) supply which I don't think you can get from the EXT port but could be derived from the 5V on the USB port.
 
Okay, thank you.
I still wonder if it can be integrated...although the board seems to have not enough free space for this
 
Btw it's seems that this modem can be directly soldered to UART! :rolleyes:

pinouts:
31-mech.jpg
 
Not Pandora's, not with a "TTL level" interface (which is probably 3.3V but 5V tolerant).. you have to do those things SteveM mentioned.
 
lyssdod said:
Btw it's seems that this modem can be directly soldered to UART! :rolleyes:
Click to expand...
UART just means universal asynchronous receiver/transmitter. It means nothing about the actual physical form of the data or the voltage levels used for such, so just saying "UART" is useless. RS232 on the other hand is a full electrical specification.

Never try to connect two devices unless you know the electrical specifications of both, otherwise you could easily damage both devices. For example, the Pandora expects 0V/1.8V signalling.
 
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So it must be Pandora's UART -> MAXIM232 -> SMTH -> Modem?
Or Pandora's UART -> Magic Level Shifter -> Modem ?

I just don't know how to solder it. I emailed radicom and they said that modem can be directly soldered in system board (what i'm dreaming of).
btw does anyone of you knows how to solder DSR, CD, RI pins etc ? I don't know how to solder it with goal of getting full-functional voice modem :(

modem link: http://radi.com/modular63.htm
 
lyssdod said:
So it must be Pandora's UART -> MAXIM232 -> SMTH -> Modem?
Or Pandora's UART -> Magic Level Shifter -> Modem ?

I just don't know how to solder it. I emailed radicom and they said that modem can be directly soldered in system board (what i'm dreaming of).
btw does anyone of you knows how to solder DSR, CD, RI pins etc ? I don't know how to solder it with goal of getting full-functional voice modem :(

modem link: http://radi.com/modular63.htm
Click to expand...
You'll need to design and manufacture an adaptor board for this if you want it to work. It will need
1. A TXB0104 level converter (will give voltage conversion for RXD,TXD,CTS,RTS - thats what we have on the pandora serial port, other pins you will need to either set to a level or leave N/C... mostly means that you wont have RI input, but its mostly used to wake up devices anyways (eg. you'll still get "RING" on the serial port anyways))
2. A 2.8V to 3.3V boost converter (and its needed accessories)
3. An 1.8V voltage regulator (to supply logic level to one side of the TXB0104).
4. Connectors for everything.
5. Other stuff you want to connect. I read that it has a SPKR output, that might be possible to put into a line-in channel for example...

Power-wise it seems that the ext port should be able to supply enough power for the modem. It has 200mA 2.8V, with 80% conversion efficiency (worst case estimate) that should be >135mA at 3.3V. The modem has maximum current consumption of 78mA, so it should roll...
 
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So wait, you want your pandora to be a wired telephone or some kind of answering system? I don't think you'll get audio directly out to the modem over serial, just nasty sounding data carrier.

What might work better is that I believe the ext port has line in and line out. You could connect some adapter to that and connect it straight to the phone line, then be able to listen/record and output audio over that.
 
I assumed he wanted to use a 56K modem as a 56K modem. For what reason I dont know, but they still have their uses in some places.
 
It's always nice to have a backup just in case. If you have a power blackout in a rural region the analogue phone often still works so you can still use a dial-up connection to satisfy your internet addiction :p
 
mali said:
It's always nice to have a backup just in case. If you have a power blackout in a rural region the analogue phone often still works so you can still use a dial-up connection to satisfy your internet addiction :p
Click to expand...
And how do you power the modem? :p
 
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mali said:
^ Via UART :p
Click to expand...
facepalm :p, this is just so wrong in so many levels.
UART = "Universal asynchronous receiver/transmitter". That means nothing as far as the electrical specifications go. It doesnt mean RS-232.
No specifics on whether you can get any power from it, but that well its a data, not a power transfer method. Also, a normal RS-232 line would not be able to power that modem. (Devices that draw power from a serial port exist, but are few. The only notable example i can think of is a serial mouse, and that needs very little power, but still its quite close to the limit of a serial port.)

Anyways, the original posters modem module could be powered by the pandora's EXT port, so with the pandora's big battery, it could be used to get internet access from a blackout if the phone system is still operational.
 
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