The ARM Development Board does not work for several reasons

Just welded 5 pieces of arm (LPC2478) of the Development Board, on the program test, found that only one board to work the other four all the rest of the dish. Hard to find a while finally found that the board of a resistance welding turned. Because it is 1206 of the package and a resistor on the PCB placed on the position of a square, it was to be placed horizontally, welding when welded into the vertical. Because a resistor is incorrect, the power-on reset function of the circuit fails , the board will not be happy to work.

From the experience of commissioning the board in recent times, to find out that the design of the ARM Board (single-chip board) does not work the reasons should be determined from the following aspects:

1, test the power supply circuit is working, the output power is stable, the output power value is correct.

2. Test whether the crystal of the board is vibrating.

3, repeatedly check the board's reset condition is satisfied, is the power-on reset, or manual reset, confirm the reset circuit is correct.

4, check the 232 serial chip is good or bad, confirm that the serial circuit design is correct.

2B errors committed during the course of the work:

Design a single-chip microcomputer development Board at once. Directly from the ad library to choose a similar stc89c51 schematic diagram, the peripheral circuit and the minimum system have been designed, after the PCB finished (SCM package is also obtained from the library), it is assumed that their PCB is correct, and then issued to do. When you come back, the system doesn't work. Finally found that the original is bought STC89C51 and PCB on the pin is not the corresponding , the harm I again made a board. Think about it and feel good 2.

Board back after the tune, or do not work, and finally found that you are the chip MAX232 bad , as to how bad is not clear, may be their own welding level too vegetable, it burned out, it may be other reasons. Because the oscilloscope sees that 232 of the receive Pins are always receiving data.

In the packaging of the painting components must make the pin label of the package and the schematic pin of the component is consistent , otherwise the schematic diagram into the PCB will appear a lot of errors.

The ARM Development Board does not work for several reasons