HAC-UM96 COM2 seemingly not really RS232 compliant

Wireless & IoT
1

I was having problems using the UM96 COM2 port jumpered for “RS232” operation. It would work with some devices but not others. Further investigation showed that the idle state of the lines was 0V, not -3 to -12. (I didn’t have access to a scope to check the high state.)

Replacing COM2 with a MAX232 level converter connected to the COM1 (TTL) lines solved the problem.

Perhaps Spark Fun could investigate and comment? The advertising for this part, “This unit can be attached … directly to RS232 for incredibly simple serial cable replacement!”, may not be entirely correct.

2

Good to know. We’ll have a look at it.

What RS232 device where you attaching it to that gave you the problem?

-Nathan

3

The device that didn’t work has a MAX3221 on the RS 232 lines. It would be a simple experiment to hook a 3221 up to the UM96, send some traffic from another UM96, and examine how the TTL side of the 3221 reacts.

4

sparky:
Good to know. We’ll have a look at it.

What RS232 device where you attaching it to that gave you the problem?

-Nathan

any update on this?