UART protection

I want to connect the UART of the micro (LPC2100) to a cell phone serial
port. 

Both devices should probably have short circuit protection but neither use
+-15V true RS232 specs.

Do I need a line driver chip between or is there a simpler (less
cost/parts) way of making the connection?

Thanks.

Medic wrote:
> I want to connect the UART of the micro (LPC2100) to a cell phone serial
> port. 
> 
> Both devices should probably have short circuit protection but neither use
> +-15V true RS232 specs.
> 
> Do I need a line driver chip between or is there a simpler (less
> cost/parts) way of making the connection?
> 
> Thanks.
Q1: Are you in the US ?
Q2: Which cell phone ?

don

Medic wrote:
> I want to connect the UART of the micro (LPC2100) to a cell phone serial
> port. 
> 
> Both devices should probably have short circuit protection but neither use
> +-15V true RS232 specs.
> 
> Do I need a line driver chip between or is there a simpler (less
> cost/parts) way of making the connection?
> 
> Thanks.

you want to hook a micro that is known not to accept negative voltage to 
a phone that may or may not supply it. because you THINK that they have 
short circuit protection. Find out what you have and make the proper 
converter. if not one of the two will be toast.

>Medic wrote:
>> I want to connect the UART of the micro (LPC2100) to a cell phone
serial
>> port. 
>> 
>> Both devices should probably have short circuit protection but neither
use
>> +-15V true RS232 specs.
>> 
>> Do I need a line driver chip between or is there a simpler (less
>> cost/parts) way of making the connection?
>> 
>> Thanks.
>Q1: Are you in the US ?
>Q2: Which cell phone ?
>
>don
>

Hi Don,

A1: Yes
A2: iPhone

I'll try and find an iPhone teardown to see what levels Apple use on the
serial port. Just cant imagine they would level shift to try RS232 for the
serial port but dont want to chance it. 

Thanks

>Medic wrote:
>> I want to connect the UART of the micro (LPC2100) to a cell phone
serial
>> port. 
>> 
>> Both devices should probably have short circuit protection but neither
use
>> +-15V true RS232 specs.
>> 
>> Do I need a line driver chip between or is there a simpler (less
>> cost/parts) way of making the connection?
>> 
>> Thanks.
>
>you want to hook a micro that is known not to accept negative voltage to

>a phone that may or may not supply it. because you THINK that they have 
>short circuit protection. Find out what you have and make the proper 
>converter. if not one of the two will be toast.
>

Not quite. My goal is to educate myself about what is required for a
serial connection instead of just resorting to a max232 solution.

Thanks

>>>I want to connect the UART of the micro (LPC2100) to a cell phone
> 
> serial
> 
>>>port. 
>>>
>>>Both devices should probably have short circuit protection but neither
> 
> use
> 
>>>+-15V true RS232 specs.

The microcontroller needs inverters for receive and transmit

Levels can simply be adapted with resistors and diodes.

E.g. 74HC00 nand as inverter in both lines. At the microcontroler end no 
protection, at the rs232 side at least a 1K resistor in series with each 
line and one or 2 diodes at the input of the nand gate.

best regards

Stefan DF9BI

Medic wrote:
>> Medic wrote:
>>> I want to connect the UART of the micro (LPC2100) to a cell phone
> serial
>>> port. 
>>>
>>> Both devices should probably have short circuit protection but neither
> use
>>> +-15V true RS232 specs.
>>>
>>> Do I need a line driver chip between or is there a simpler (less
>>> cost/parts) way of making the connection?
>>>
>>> Thanks.
>> you want to hook a micro that is known not to accept negative voltage to
> 
>> a phone that may or may not supply it. because you THINK that they have 
>> short circuit protection. Find out what you have and make the proper 
>> converter. if not one of the two will be toast.
>>
> 
> Not quite. My goal is to educate myself about what is required for a
> serial connection instead of just resorting to a max232 solution.
> 
> Thanks
Google found these:
http://pinouts.ru/PortableDevices/ipod_pinout.shtml
http://ipodlinux.org/wiki/Apple_Accessory_Protocol

This project will help you as well:
http://www.sparkfun.com/commerce/product_info.php?products_id=8245

good luck

don