ETT boards : Mini232

Now ask yourself: How often have you needed a simple solution to go from TTL to RS232 levels? If you're an accountant, the answer is "Never" but if you're in the engineering business, chances are you have been in situations where you could use one. And in all these cases, the Miniboard RS232 from ETT would have been the solution. Look at it, here on the right. From top to bottom we see:

Two 4 pin headers that are at RS232 levels
The MAX232 converter
The four electrolytic capacitors to power the converter
The 6 pin TTL level inputs.
Power and ground are also supplied via the 6 pin connector

This all mounted on a small printed circuit board. You could keep one in your shirt pocket. ETT also produce a special 4 pin SIL to DB9 converter for a few euros.

Besides this version, that accepts 5 Volts at its input, ETT also make a 3.3 Volt version that is built around the ADM 3232 chip (which does nopt need electrolyticals anymore, but can do with simple 100 nF ceramic caps). The prices are identical : USD 5. In real money this boils down to:

This all for € 3,30!

Below is my version of the ETT manual that came with this product.

Board size : 43 x 56 mm

In Mickey Mouse units, this is 1 11/16 x 2 3/16 inch. As if that gives an impression of how small it is.

This module is a converter between RS232 and 5 Volt TTL. It is powered by a standard 5 Volt supply. It functions as a stand alone level converter between microcontroller and RS232. Each module is dual channel. Each channel is full duplex (if the Microcontroller is so too). Just connect the input labeled 'Tx' to the corresponding output of the microcontroller. So the same for the 'Rx' signal. Always combine Tx1 with Rx1 and Tx2 with Rx2. Do not mix!
The power signals (+5V and Ground) must be taken off the same supply as which is used for the microcontroller.

On the output side make sure the Tx pin goes to the correct pin in the RS232 Sub D connector. This is pin 2 for a DB9 connector. Rx should go to pin 3 of a DB9. Do not forget to connect the GROUND signal line to pin 5. Do not connect the +5 Volt line inside your connector.

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