I have an RS232 device that I want to connect to a CoBox Micro or CoBox Mini. How can I interface these device's TTL serial ports to an RS232 device?

Here's an ASCII diagram of an example circuit for the CoBox Micro. This example uses a single Maxim MAX232 chip to drive the RX, TX, CTS & RTS signals.

CoBox Micro RS232 Con1 SGD 2---------------------------------SGD Maxim MAX232 +-------+ RXA(IN) 3------------12|--o<---|13--------TX(OUT) | R1 | | | TXA(OUT) 4------------11|--->o--|14--------RX(IN) | T1 | | | RTSA(OUT) 5------------10|--->o--|7--------CTS(IN) | T2 | DTRA(OUT) 6--NC | | CTSA(IN) 7-------------9|--o<---|8--------RTS(OUT) | R2 | DCDA(IN) 8--NC | | +5Vdc +----4|C2+ Vcc|16----+------O | | | | 0.1uF = | | = 0.1uF | | | | +----5|C2- V+|2-----+ | | +----1|C1+ V-|6----||---GND | | | 0.1uF 0.1uF = | | | | | +----3|C1- GND|15--------GND +-------+

If you need the DTR and DCD signals instead of RTS and CTS you can connect them instead. If you need all 4 handshaking signals you can either use 2 MAX 232 chips or another chip with more drivers.

Maxim has several chips in it's MAX232 line with varying numbers of drivers. Maxim's web site is https://www.maximintegrated.com/en.html.

In the US you can get Maxim parts from:

• DigiKey, http://www.digikey.com/DigiKeySearch.html

• Newark Electronics, http://www.newark.com/

• Mouser Electronics, http://www.mouser.com/

• Jameco Electronics, http://www.jameco.com/

• or you favorite electronic parts vendor.

Other possibilities are:

• National Semiconductors DS14C232

• Harris HIN232 and ICL232

• Motorola ADM232

• Linear Technology LT1137A

  • The LT1137A is a little different from the MAX232.  It has 3 RS-232 outputs and 5 inputs.

[Originally Published On: 01/26/2000 08:39 AM]