The LPC1778 question of wakeup in power down mode

[zhangzhiyong]

We use the LPC1778，enter power down mode，we use CAN INTERRUPT、ACC and RTC to wake up the mcu.

Most products can be awakened normally by the above methods，But individual products can not be wakeup in any way.

The product goes to the lab, get the power back on the board, problems don't recur.

The question to ask is：In the power down mode，What are the possible causes of not be wakeup MCU? Hardware, software, environmental interference? We'll go through them all.

[Omar_Anguiano]

Hello zhiyong zhang

Since the MCU is primarily woken with interrupts, it is important to check that the reset works properly. Adding an external circuit with pull up resistors and ground capacitors will be helpful. If the circuit is no wired correctly you may experience issues with the reset signal obtaining a saw-tooth signal which is not desirable.

If the peripheral is not configured correctly you may experience some issues. The busfault and hardfault will cause the MCU to stop. Additionally, it is important to check that the supply voltage is on the recommended values otherwise the MCU will have a weird behavior.

The MCU uses the 12MHz IRC oscillator to wake up the micro, it is important that it works properly. Although the internal oscillators are precise, the temperature changes will affect its performance.

Resuming, the most important aspects for the MCU wakeup are the oscillator, supply voltage on range and that the interrupt triggers correctly.

Let me know if this is helpful, if you have more questions do not hesitate to ask me.

Best regards,

Omar