8051max232
The picture shows standard connection between 8051 and DB-9 via MAX232. 14th pin is the translated output of the transmitted data by 8051, so this should be connected to the receiver pin of DB-9, which is pin 3, but here it goes to pin 2, which is called 'transmitted data', so should we read "transmitted data=receiver of DB-9" and "Received data=transmitter of DB-9"? Because, to me the DB-9
Label seems opposite as expected.
Okay, for anyone that ever encounters something like this in the future:
The issue was that there was leakage from the power trace into the serial trace, such that a 60Hz wave was appearing on the SPI line, which obviously would mess things up.
I know the likelihood of this same fix applying to other people is small, but maybe it will at least give you some ideas!
It will be essential to know the size of the data read from each sensor, how many sensors and how fast of repetition rate that you need to get the data into the PC. Without that data it will be difficult to recommend an exact solution.
That said it may be reasonable to suggest that you configure your 8051 UART port's TXD and RXD lines to talk to a 1x6 header that can mate to one of these cables:
This can then plug into your PC's USB port. Using the appropriate virtual comm port driver from the FTDI web site the solution can easily transfer data in serial manner from your 8051 to the application in the PC. The PC app thinks it is simply talking to a COM port.
These serial adapter cables can easily transfer serial data at rates to 230.4 K baud. Using a standard 8N1 serial framing this baud rate translates to a just over 23000 bytes per second of raw transfer rate. If you had 12 sensors, each with two bytes of data and you wanted to update the data to the PC at 100 times per second this would equal an application data rate of 12*2*100 = 2400 bytes per second. As you can see there would be plenty of remaining bandwidth on the virtual comm port channel to wrap a protocol around your application data and send it to the PC.
Best Answer
There's 2 common pinouts for DB9 RS232,
Data Terminal equipment(DTE) andData Circuit-terminating Equipment(DCE).DTE is the male DB9 pinout typically found on PC's. DCE is the female DB9 pinout found on various RS232 devices such as modems.
The pinouts for DTE and DCE are such that the transmit pin on the one type matches the receive pin on the other type and vice versa... Connecting 2 DTE devices together (such as 2 PC's) requires what is known as a "null-modem" cable that crosses RXD and TXD.
As you can see, your schematic above matches the pinout for the DB9 Female DCE. This allows the device to be connected to a PC (DTE) with a normal 1 to 1 male-female DB9 cable.