Javier Rod wrote:
> Hi!!
>
> I'm experiencing the problem that when I connect an ULN2803 to a LPC2129
> ports the MCU doesn't start, and when unplugged such a driver from its
> socket, the MCU starts to work as usual.
>
> The eight lines goes directly from P0.11 to P0.18 to each input of the
> driver. If I just connect any single pin of the MCU to any single input
> of the driver, the MCU doesn't start!!. I read that P0.14 is needed to
> enter into debug mode (or something like that), but for example, if only
> P0.11 is connected to the I0 of the driver, the MCU doesn't start, and
> so do the rest of the pines. Even more, P0.11 to P0.18 had been set as
> inputs, but this still doesn't work. I've placed the lines that
> initialize those terminals in several parts of my code, without good
> results. My reset line has a 10K resistor and a 1uF tantalium cap tied
> to ground.
>
> Moreover, when debugging under CrossWorks this works fine, but when
> stand-alone this didn't.
>
> Is there something wrong with this MCU when interfacing with such a
> drivers?? Do I need to add pull-down resistors??
>
> Thanks!!

Hi again!!

I guess I solved my problem. The ULN2803 input resistors tied P0.14
down, so it started the serial bootloader mode. I add a 4K7 pull-up
resistor and now it seems to works in stand-alone mode. This is a
thermal printer driver, but it doesn't want to print anything (it does
under CrossWorks), but that's another history.

Thanks for reading the post!!