Making pins low and outputs at startup on an lpc1343

[lpcware]

Content originally posted in LPCWare by canisrays on Mon Dec 17 21:44:02 MST 2012
Is there a means to specify LPC1343 pins be pulled low and made outputs vs inputs and floating at startup?

We have a circuit that for safety reasons at boot must keep some pins pulled low. The LPC1343 by default seems to make the pins inputs and floating at boot.


Setting the pins to outputs and low as soon as user code execution starts is not an acceptable solution because this does not resolve the issue of the pins being inputs and floating when the uC enters one of the bootloader modes (SPI, jtag, usb msd).

[lpcware]

Content originally posted in LPCWare by graynomad on Wed Dec 19 01:08:58 MST 2012
I hope you haven't laid out the PCB yet :)

[lpcware]

Content originally posted in LPCWare by canisrays on Tue Dec 18 23:01:07 MST 2012
Darn, that was what I was afraid of.

The behaviour now is quite interesting. The pins are connected to op-amps (non-inverting) to output 0v (a logic low output on a lpc1343 pin) or 5v (a logic high on a lpc1343 pin)

After setting the pins to be outputs in user code, this works as expected...

At startup is another beast. I'm seeing readings of +11v without a pull-down resistor. With a pull-down resistor I see -0.2v.

[lpcware]

Content originally posted in LPCWare by graynomad on Tue Dec 18 01:25:33 MST 2012
External pull down resistors. Until you have control of the pins there's nothing else you can do.

[lpcware]

Content originally posted in LPCWare by serge on Tue Dec 18 01:24:44 MST 2012
Try pull-down resistors perhaps?