MAX3232E: The MAX3232EIDBR do loopback test and sometime will have data loss.

Hi Bogey,

These waveforms both show normal voltage levels, so it isn't clear what would be causing errors.  The plots are very zoomed out, though, so it isn't possible to observe the signal timing in detail.  Can you please check the failing data lines using a finer scope timebase?  It would also be good to trace the whole signal path from the TXIN to TXOUT and from RXIN to RXOUT.  Also, can you please describe how the loopback test is configured?  I.e., which TX signals are connected to which RX signals?

Regards,
Max

Hi Max 

Thanks for your reply, sorry for i am not familiar MAX3232, may i know form the waveform, i can check Datasheet which item to judgement its pass or fail?

If you can example to us is better. loopback is test software.

                                                                    Bogey

Hi Bogey,

What I mean is that you could look at each signal as it goes through the system to see if there is anything wrong.  For a loopback test, the transmit outputs of the UART should make it back to the receiver input.  So, you can first check the signal on TXD0 (for example).  If the MAX3232E is working, you should see each high bit on TXD0 translate to a negative voltage (< -5 V) on TTXD1 for the same duration.  Similarly, each low bit on TXD0 should correspond to a positive voltage (> 5 V) on TTXD1.  If you don't see this, then there is an issue with the transmitter.

Then, you can check to see if the waveform matches on TTXD1 and RRXD1.  If not, then there may be a problem with the loopback path and you could check the cable connections.

Then, you could check to make sure each positive voltage period on RRXD1 corresponds to a low bit period on RXD0 and each negative voltage on RRXD1 corresponds to a high bit period on RXD0.  If not, then there is an issue with the transmitter.

You could look at each UART signal this way to verify the signal integrity.

If that all looks OK, you might try operating at a lower baud rate.  If that makes the system work, then maybe there are some timing issues at the higher baud rate to debug.

Let me know if this doesn't make sense.

Regards,
Max