topic Re: pwm pin and reset problem in LPC Microcontrollers

pwm pin and reset problem

lpcware — Wed, 15 Jun 2016 17:05:33 GMT

Content originally posted in LPCWare by enrico cortelazzo on Wed Mar 25 02:33:33 MST 2015
Hello,
I have a problem with PWM pin during reset:
at start-up all the pins are in high impedence input state with pull-up inside and for this reason I configure my PWM as "active low" in my board.
I configure SCT_OUT pin for drive an inverter and use two events/state, the first for drive low the pin and the second to reset pin high. It works fine, but now I have this trouble:
if it happens a reset condition all the register about the SCT timers go to its reset condition and my output pin goes in low state, but switch matrix is not involved in this kind of reset so my pin remains low and the inverter hardware is on, in a dangerous condition.
Pratically there are two different condition for output pwm at reset state: high state at start-up reset and low state for other reset (wcd for example).
Someone has a suggestion for solving this trouble?
thanks
enrico

Re: pwm pin and reset problem

lpcware — Wed, 15 Jun 2016 17:05:34 GMT

Content originally posted in LPCWare by R2D2 on Wed Mar 25 21:07:13 MST 2015

Quote: enrico cortelazzo
I configure SCT_OUT pin for drive an inverter and use two events/state, the first for drive low the pin and the second to reset pin high.

I'm not sure how you setup your SCT in detail :((

Could be useful to post a project to see what is happening there :)

Re: pwm pin and reset problem

lpcware — Wed, 15 Jun 2016 17:05:34 GMT

Content originally posted in LPCWare by starblue on Thu Mar 26 01:18:27 MST 2015
How about using a relatively strong pull-down and active high signals?

Re: pwm pin and reset problem

lpcware — Wed, 15 Jun 2016 17:05:35 GMT

Content originally posted in LPCWare by enrico cortelazzo on Thu Mar 26 04:21:54 MST 2015

you can configure pull-down only after reset, so at start-up the pin is high.
The preblem is that we have 2 different conditions for pwm output pin at reset:
high state (pull-up) at start-up
low state at other reset
I think the only solution is to add other hardware to enable/disable pin between micro and the other; it's a pity!

Re: pwm pin and reset problem

lpcware — Wed, 15 Jun 2016 17:05:36 GMT

Content originally posted in LPCWare by R2D2 on Thu Mar 26 05:03:34 MST 2015

Quote: enrico cortelazzo
you can configure pull-down only after reset, so at start-up the pin is high.

It is input and pulled up with internal weak pull-up :)

Quote: enrico cortelazzo
I think the only solution is to add other hardware to enable/disable pin between micro and the other; it's a pity!

:quest:

And I think the fastest solution is to pull this pin up/down with an external (strong) resistor :O