GPS RS232 Dev Board

  
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Once you discover how to setup an RS232 connection, it`s really just cut-and-paste for future projects. Please note this is a relatively compact SMD version of the power supply. This can easily be obtained with through-hole components using a breadboard. Here is theschematic: The D3 large diode MBRA140 is for reverse protection. It can handle up to 1A and prevents damage to the board if a center-negative wallwart
GPS RS232 Dev Board - schematic

is attached. This diode will cause a ~0. 5V drop from whatever the wall-wart is outputting. U1 is the LM317 (or LM1117 in SMD form) adjustable voltage regulator. It will take in some larger voltage and output a set voltage. The output voltage is set with two external resistors. R1 is historically 240 and value for R2 is different for different required output voltages. In our case, we want 3. 3V out of the regulator, so R2 is set to 715. The LM317 is good because it is variable, the SOT-223 package is nice becuase it can take a relatively large voltage on the input (25V max I believe ) and has decent heat dissapation. J2 is just a two pin polarized header so that you can either `steal` 3. 3V from the board to power other boards, or have other boards power this board without the need for the external wall wart. This shows the DB9 connector (also known as a D-Sub 9-pin connector), serial cable, and MAX3232 IC and charge pump caps (all SMD, again, can be done with PTH components). Here is the schematic: Now read-up on the MAX232 IC. It could be the most common IC out there, at least for the embdded world. This IC will have many different model names (ICL232 for example) but all do the same thing, and will most likely have identical pin-outs. This IC is used to take low voltage signals from your micro or PIC or ARM or whatever, and converts those low-voltage signals to higher-voltage signals that the computer can understand....



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