Posted on Feb 6, 2014

When starting with Arduino, one soon has much more Arduino boards then RS232 or even USB ports on the computer. So that, it seems more useful to put the signal level converter to an external adapter than directly on the Arduino board. Usually, one has (I have) a big basket full of ATMEGA8 and ATMEGA168 with Arduino bootloaders and one idea. So I n

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eed a simple and fast-to-build Arduino board. When the bootloader is already programmed, one does not need the ISP port. Also, I prefer an external RS232 level converter than to build it on the Arduino board, since then the usage is more flexible. When connected to a PC via CAT, many mobile phone use a serial protocol and TTL signal levels. At many of these CAT adapters, the connexion to the operating system is done with a virtual COM-port. So we may have exactly the thing we want for our Arduino: A COM-port with TTL signal levels via USB. The first step should be the installation of the COM driver. When opening, one needs a way to find the meaning of the connectors. One possibility is to look out for a scheme of the connector and mark the wires. Another, maybe faster, way is to identify the pins by oneself: The first thing to find out which is the ground pin. Usually, it`s the one having the most connections with the connector. It`s not necessarily connected to the ground or shield of the USB plug! Then, plug-in the connector and watch out if one of those pins is a 5V VCC pin. Should be easy to find out with a multimeter, when you know the GND pin. If there are only three wires, you can do without this step :-).

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