Raspberry pi zero

The raspberry pi and especially the -zero variant is a really simple board. There is not a "serial chip" that this RX pin connects to. The serial lines go directly into the CPU.

It is also extremely unlikely that say a short has developed on the board. So the only thing that seems reasonable is that your CPU has developed a short on the RX pin.

There is only one option  that I can think of that might have caused this: Illegal voltages at the RX pin. These are documented to "reduce reliability a lot", and that's what you seem to be seeing.

The voltage at the RX pin should be between 0 and 3.3V at all times (that's what we mortals are supposed to attempt). The official specs will state something like ABSOLUTE MAXIMUM RATING: min -0.3V max: 3.6V.

So... what are you using to drive the serial signal into the pi? Something that runs at 5V? Or maybe there are long lines between the two devices and some EMC events slowly wear down the pi?

rew Sir, I have Connected TX, RX pins to RS232 IC setup along with USB to RS232 converter cable. Raspberry pi itself supplying the voltages to drive serial signal.

So what you're saying is that you have an USB-RS232 converter that allows you to set the IO voltages on the non-USB  side(*). And you're saying that you used a voltage output from the pi to set the IO voltage.

Now the question remains: did you use 3.3V or 5V? (3.3V is pin 1 on P1, 5V is pin 2 and pin 4 on P1).

(*) if the signal levels are not -12V for "1" and +12V for "0" then you can't really call it RS232.

rew Sir, my RS232 Chip circuit is well Tested and Signal Levels are also as per Required.

As i mentioned before that my serial Transmission was working well on my Raspberry pi zero.

All of a sudden something happened and raspberry is now only Transmitting the Data but not receiving it.

And also 5V supply voltage RS232 chip is given from Raspberry pi VCC (Physical pin no. 2).

Sir, The raspberry pi foundation has not released full formal electrical specifications for the chip. But they have said: if you supply 5V signals into the raspberry pi CPU, the chip will have a reduced lifetime.

I have in the past accidentally supplied 5V signals into the raspberry pi. I have then noticed that and quickly disconnected what shouldn't have been connected in the first place. So far this has not resulted in my raspberry pi breaking down.

You have confirmed to me that you're sending 5V signals into the raspberry pi.

You have confirmed to me that you've tested this for a while.

The foundation says that it won't die immediately. My experience confirms that.

The foundation says that it will die quicker than when you provide appropriate 3.3V signals. Your experience confirms that.

Sir, you have, by your own actions, blown up your raspberry pi.

The good news is that it's only one pin. The bad news is probably that you NEED that pin for your project. Sorry about that.

rew  Thank you so much for all the help sir.

condolences to my raspberry pi 

rew Raspberry Pi Sir, Have one Question in my Mind. Can i use any other GPIO on Raspberry as SERIAL RECEIVE PIN. I understand technically its not possible,  but still if there is any way ? please suggest. Thank you in advance

The GPIO pins are "general purpose".... you can do anything with them. But you have to write software to do that. And  often what you want to do is easy to do in hardware and many people use it, so they make a hardware module that can do it.

This is the case for the serial port. The protocol (start out with the line high, then pulse it low for one period, then pulse each of the bits and then go high again for at least one bit period) is common and easy enough to warrant hardware. Now they COULD make the chip so that you can route all pins to each of the hardware modules. (besides "serial" there is SPI and I2C for example). But that's expensive in terms of chip space. And in most cases not necessary.

So as an example the chip maker may tell you: If you want serial that can be on pins 1 and 2 or 4 and 5. SPI can be on 4-5-6, or on 7-8-9. If now I2C can go on 1-2 or 7-8, you'd have the situation that you can chose any two of these modules but not all three. Of course in practice, things are more complex, with more options and more peripherals things get more complex. But also you get the situation that almost always you can find a solution provided you don't need ALL peripherals at the same time.

Anway..... I looked up the options for your RX signal. It is normally on pin GPIO15. pin 10 of the P1 connector. But you can also configure it on pin GPIO33, GPIO37 or GPIO41. None of these are broken out on the P1 connector. :-(

rew Thank you so much for the Information. so I can use pin 15 Directly as RX or I have to make changes in any kind of software?

like in /boot/cmdline.txt or anywhere else?

GOIO15, which is pin 10 on the P1 connector is the one that is broken. It is the default location for the RX.