Lpc2000

Hello,

I am experincing a strange problem on a LPC2212.
Sometimes, after board power-up, the micro does not start at all and 
seems to remain in a pseudo-reset state (all pins in high-z).
The software execution seems not to start at all, since one of the 
first thing done is to program some of the GPIO as outputs.
I checked the state of the BOOT pins related to RESET pin and power 
supplies but everything seems to be ok.
RESET is released when all the configuration pins are in the correct 
position.
JTAG pins are polarized with pull up/down resistors.

The problem seems to be somehow related to the UART0 (the problem 
appears when the board is connected to a PC through a serial cable).

Any suggestion will be greatly appreciated.

Thank you.

Hi,

> I am experincing a strange problem on a LPC2212.
> Sometimes, after board power-up, the micro does not start at all and 
> seems to remain in a pseudo-reset state (all pins in high-z).
> The software execution seems not to start at all, since one of the 
> first thing done is to program some of the GPIO as outputs.
> I checked the state of the BOOT pins related to RESET pin and power 
> supplies but everything seems to be ok.
> RESET is released when all the configuration pins are in the correct 
> position.
> JTAG pins are polarized with pull up/down resistors.
> 
> The problem seems to be somehow related to the UART0 (the problem 
> appears when the board is connected to a PC through a serial cable).

do you have some sort of Reset/Enable Bootloader mechanism controlled
by RS232 lines?

--- In lpc2000@yahoogroups.com, "extra300_it" <roberto.labaa@...> 
wrote:
>
> Hello,
> 
> I am experincing a strange problem on a LPC2212.
> Sometimes, after board power-up, the micro does not start at all 
and 
> seems to remain in a pseudo-reset state (all pins in high-z).
> The software execution seems not to start at all, since one of the 
> first thing done is to program some of the GPIO as outputs.
> I checked the state of the BOOT pins related to RESET pin and power 
> supplies but everything seems to be ok.
> RESET is released when all the configuration pins are in the 
correct 
> position.
> JTAG pins are polarized with pull up/down resistors.
> 
> The problem seems to be somehow related to the UART0 (the problem 
> appears when the board is connected to a PC through a serial cable).
> 
> Any suggestion will be greatly appreciated.
> 
> Thank you.
>

If you are using two PCs, the problem might be something to do with 
the three ground connections - PCs and board power supply.

Leon

--- In lpc2000@yahoogroups.com, "Uwe Arends" <nospam@...> wrote:
>
> Hi,
> 
> > I am experincing a strange problem on a LPC2212.
> > Sometimes, after board power-up, the micro does not start at all 
and 
> > seems to remain in a pseudo-reset state (all pins in high-z).
> > The software execution seems not to start at all, since one of 
the 
> > first thing done is to program some of the GPIO as outputs.
> > I checked the state of the BOOT pins related to RESET pin and 
power 
> > supplies but everything seems to be ok.
> > RESET is released when all the configuration pins are in the 
correct 
> > position.
> > JTAG pins are polarized with pull up/down resistors.
> > 
> > The problem seems to be somehow related to the UART0 (the problem 
> > appears when the board is connected to a PC through a serial 
cable).
> 
> do you have some sort of Reset/Enable Bootloader mechanism 
controlled
> by RS232 lines?
>

Yes, but I disconnected the cables that brings my MCU in BOOT mode.
So now I have only RS-232 TX, RX and GND connected.
It doesn't seem to enter boot mode, since it does not respond to ISP 
commands.

Have you looked at the comm lines and ground with a scope for the presence 
of excessive noise?

[Non-text portions of this message have been removed]

--- In lpc2000@yahoogroups.com, mfrazier@... wrote:
>
> Have you looked at the comm lines and ground with a scope for the 
presence 
> of excessive noise?
> 
> [Non-text portions of this message have been removed]
>

I had a similar problem last month.  A small amount of current got 
through the RS232 driver chip and into the 3.3V power rail, so that 
when the DC power to the CPU was off, it did not go to 0V.  The CPU 
must go down to 0V when it is powered off, and if it drifts around .5-
1V, something internal to the CPU latches up.  You can put a pull-down 
resistor on the 3.3V to verify that this is the issue.

Yes, this is the reason for the faulty reset (I discovered myself, 
but thank you all the same).
In my case the TX of the PC RS-232 goes through the drivers and 
apllies a little negative voltage on 3.3V (around -200mV).
This makes (sometimes) the reset fail.


--- In lpc2000@yahoogroups.com, "johnsonnenberg99" 
<johnsonnenberg99@...> wrote:
>
> --- In lpc2000@yahoogroups.com, mfrazier@ wrote:
> >
> > Have you looked at the comm lines and ground with a scope for 
the 
> presence 
> > of excessive noise?
> > 
> > [Non-text portions of this message have been removed]
> >
> 
> I had a similar problem last month.  A small amount of current got 
> through the RS232 driver chip and into the 3.3V power rail, so 
that 
> when the DC power to the CPU was off, it did not go to 0V.  The 
CPU 
> must go down to 0V when it is powered off, and if it drifts 
around .5-
> 1V, something internal to the CPU latches up.  You can put a pull-
down 
> resistor on the 3.3V to verify that this is the issue.
>