MAX3232: MAX3232CDR not supporting for 115200 bit/s data rate

Please show an oscilloscope trace of the input and output signals.

Are all the capacitors near the chip?

Hi Dattaatray,

As Clemens mentioned, Can you provide scopeshots? Can we also review the schematic?

Are you also doing any kind of loopback test or is your test done through a cable to another RS232 device?

-Bobby

Dear Clemens,

All capacitors are close to the chip. In one PCB, we used three RS232 port. On all ports found same issue.

Thanks.

Regards,

Dattatray

WA : +91 8087590560MT_2021_0007_R6_v1 2.sch

Dear Bobby,

We did in both way. Same result found.

Dattatray

Please note that T2IN must not be left floating.

Please provide the oscilloscope traces.

Hi Dattatray,

Dattatray Salunke said:

I reviewed the schematic here but don't see any big red flags that would indicate failed RS232 communication. 

As Clemen's pointed out, the TIN pins should be biased to something to ensure they don't float around and cause toggling to occur on the output pins but I don't immediately expect that to result in failed RS232 communication. 

Can you do a loopback test by shorting the RS232 TOUT pin to RIN pin? Please send a byte like 0x55h or 0xAAh

Get a scopeshot of the TIN, RIN, V+, and V- pins all in one shot. 

-Bobby

Dear Bobby,

Please refer below waveform with 0x55.

1. Pin no 11 (T1IN), 0x55, 115200, pin no 13,14 short

2. Pin no 13(R1IN), 0x55, 115200, loop back test

3. Pin no 2. V+

4. Pin no 6 :V-

Regards,

Dattatray