Did you verify that the tx pin from the MCU side is shorted with the corresponding MAX232 pin? Are pulses produced on MCU tx pin? If not, then it sounds like there is a software problem. Or the tx line is shorted with something else on the board. To check this out you could use the tx pin as GPIO pin. Produce pulses from software. If pulses are actually produced, then there is a bug in the UART code. If not, then possibly there is a short circuit somewhere.pashok84 said:When connected rx and tx of TTL side. then also no results. I monitor the rx ttl pin in oscilloscope. it is working. Tx is not working.
So it looks like you didn't follow exactly the circuit provided in the datasheet after all. Because the schematic uses 5V supply. Also it is given in the datahseet that supply must be 5V (4.5V to 5.5V). I don't know if this is the problem, but in any case you have violated specifications.pashok84 said:i am using MAX3232 with 3.3v power supply.
when i connect a jumper for loopback,
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