Serial adapters

OLPC has 2 different serial adapters for getting serial output from the laptop.

The original adapter that came with the ATest boards

Original Serial Adapter

and the new universal adapter [pic_of_new_adapter].

The original ATest adapter is very simple and only does TTL<->RS232.

The new adapters are able to do TTL<->RS232, TTL<->USB, and RS232<->USB. In the RS232 modes they are able to work with both straight and NULL modem cables. Because of this they are a bit more complicated than the ATest adapters.

This complexity is in the form of 2 jumper blocks on the adapters. Blocks J4 and J6.

J4: Mode select block

J4 selects between the 3 modes of operation.

Mode 1: TTL<->USB

• Jumper 1&2, 5&6

Mode 2: RS232<->USB

• Jumper 3&4, 7&8

Mode 3: TTL<->RS232

• Jumper 2&4, 6&8

J6: Null Modem block

In the RS232 modes 2 & 3, J6 will swap the TX and RX lines. Normally changing these jumpers is not necessary.

• RS232 NULL Modem: 1&2, 5&6
• RS232 Normal: 3&4, 7&8

To make the adapter appear a like a serial port you would find on a PC you would use normal wiring. Connection between the adapter and the PC would use a NULL modem or crossover cable.

If you are using a serial cable that is wired to be straight thru then you would use NULL modem wiring.

If you are using Mode 1 then the settings for J6 do not make any difference because the DB9 is not used.