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Forum: µC & Digital Electronics Reset on LPC1768


von Prakash R. (Company: Coinel Technology Solutions) (prakash)


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Hello,

I am using LPC1768 and programming it using ISP. What i have observed is 
that the programs that i load work fine but when i repower the LPC 
board, the code starts to work only after a reset.

The code executions should start after powerup.

Kindly let me know what could be the possible issue.

: Moved by Admin
von M.K. B. (mkbit)


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Hello,

to me it looks like a problem with the power supply.

If you switch on the power, all the devices in your circuit draw 
current. If this ist too much and the voltage drops below a certain 
level, the controller might end up in an undefined state.

Solution might be too change something on your power supply. Or maybe 
there is a parameter to delay the startup of your controller.

I hope this will help you!

von Lutz (Guest)


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Have you enabled the brown out detection? Another possibility is the 
power supply: If you only switch off the power for a few seconds there 
may be capacities in the circuit which holds the power on a sufficient 
level. As a result the µC doesn't recognize the power loss.

von Martin T. (mthomas) (Moderator)


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Are there any loops in the initialisation which wait for bits to be 
set/cleared by the hardware (something like while 
(!(SOME_REG&SOMEMASK)){;})? IF so, check with "LED-blink-debugging" if 
the code "hangs" in such a loop. Did you try with the ISP interface 
connected and disconnected. Did you check the VCC, BSL and RST levels 
with a scope? Do you use code from NXP's CMSIS package to init the 
clock-system? If not, you may at least do a few tests with the code from 
the package.

von Prakash R. (Company: Coinel Technology Solutions) (prakash)


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Mk Bit wrote:
> Hello,
>
> to me it looks like a problem with the power supply.
>
> If you switch on the power, all the devices in your circuit draw
> current. If this ist too much and the voltage drops below a certain
> level, the controller might end up in an undefined state.
>
> Solution might be too change something on your power supply. Or maybe
> there is a parameter to delay the startup of your controller.
>
> I hope this will help you!

Thanks for your response. Ya it looks like problem hardware only.

I have herewith attached the circuit, It would be great if you check 
this circuit

The reset and isp circuit i have uploaded to this link
The RST# goes to controller pin 17.

von TL431 (Guest)


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Is R22 470 Ohms? Together with the 10k (R21) the Reset Voltage might be 
very low.

von Prakash R. (Company: Coinel Technology Solutions) (prakash)


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Martin Thomas wrote:
> Are there any loops in the initialisation which wait for bits to be
> set/cleared by the hardware (something like while
> (!(SOME_REG&SOMEMASK)){;})? IF so, check with "LED-blink-debugging" if
> the code "hangs" in such a loop. Did you try with the ISP interface
> connected and disconnected. Did you check the VCC, BSL and RST levels
> with a scope? Do you use code from NXP's CMSIS package to init the
> clock-system? If not, you may at least do a few tests with the code from
> the package.

Thanks for your reply.

There are no loops in the initialization.

I have checked the VCC, BSL, RST lines

BSL line: default -> 3.1v
          After ISP switch - 0 -> 3.1v (the value changes from low to 
high)

Vcc line: Default -> 3.3 v
          After Reset - 3.3v

RST line : Default -> 1.7v
           After Reset - 0 -> 1.7v (the value changes from low to high)

RST out Line: Default -> 3.2v
            after reset - 0-> 3.2v (the value changes from low to high)

These lines seems to be working fine, Any suggestions to the possible 
problem??

von hamid (Guest)


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helloo
i have a challenge with lpc 1768 reset.
 in several case when i reset  this processor via  the  reset pin and 
connect it directly to gnd the ic  will crashed and burnes.so that for 
avoiding ic failing i should reset the ic reset pin via the resistance.

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