LPC 55S16 - Auto Reset issue

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LPC 55S16 - Auto Reset issue

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Dhaya
Contributor III

Hi,

    We have customized design board with LPC55S16. To flash the code, we separate the JTAG wires to program in SW and JTAG mode. This JTAG includes RESET, SWO, SWD, TRST, TDO, TDI pins. 

    We use mains and battery mode for power supply. During this power switching, controller get resets. We suspect on RESET pin which cause this issue. While RESET pin maintain in open state there is no such issue. But while we connect the wires, this auto reset is happened.

   How we can avoid this issue?

 

Dhaya_0-1685181927430.pngDhaya_1-1685181948737.png

 

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1 Solution
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xiangjun_rong
NXP TechSupport
NXP TechSupport

Hi,

Regarding your question, first of all, for LPC552x, the JTAG port is only used for boundary scan, it can not be used to download code and debug, you have to use SWD port for downloading/debugging.

xiangjun_rong_0-1685323423281.png

Secondly, I have checked your schematics, I think it is okay, a 22uF capacitor must be connected to end of inductor L1 for the on-chip DC/DC converter, I suppose you have connected it, but does not display.

for your issue "We use mains and battery mode for power supply. During this power switching, controller get resets.", you do not draw the mains and battery power on the posted schematics, if both the mains and battery power supply are 5V, I suppose that you can connect two diodes and a large bypass capacitor.

This is the our EVK schematics with multiple power sources.

xiangjun_rong_1-1685323876706.png

one of the 5V power supplies is from external power connector, another is from USB port.

Regarding the Reset event, I suppose that the power switching is not smooth, there is a power supply voltage drop, which leads to reset event by the on-chip BOD(Brown-out detector) module.

If it does not answer your question, pls update the ticket.

Hope it is helpful

BR

XiangJun Rong

 

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acosara
Contributor III

Section 48.4.64 of the User Manual needs to be corrected then. It implies you can flash the MCU through JTAG. 

acosara_0-1697744816977.png

 

416 Views
xiangjun_rong
NXP TechSupport
NXP TechSupport

Hi,

Regarding your question, first of all, for LPC552x, the JTAG port is only used for boundary scan, it can not be used to download code and debug, you have to use SWD port for downloading/debugging.

xiangjun_rong_0-1685323423281.png

Secondly, I have checked your schematics, I think it is okay, a 22uF capacitor must be connected to end of inductor L1 for the on-chip DC/DC converter, I suppose you have connected it, but does not display.

for your issue "We use mains and battery mode for power supply. During this power switching, controller get resets.", you do not draw the mains and battery power on the posted schematics, if both the mains and battery power supply are 5V, I suppose that you can connect two diodes and a large bypass capacitor.

This is the our EVK schematics with multiple power sources.

xiangjun_rong_1-1685323876706.png

one of the 5V power supplies is from external power connector, another is from USB port.

Regarding the Reset event, I suppose that the power switching is not smooth, there is a power supply voltage drop, which leads to reset event by the on-chip BOD(Brown-out detector) module.

If it does not answer your question, pls update the ticket.

Hope it is helpful

BR

XiangJun Rong