Hi,
we are encountering similar issues in the moment. We do have professional build prototypes and we do have different behaviour due to power up / power down sequence using pwrkey line.
- 1st prototype is working as expected and we can power up and power down the modem just like expected.
- 2nd prototype is working on power up of the complete device also as expected, but if we power down the modem by pulling pwrkey for 750ms it happens in every 3rd or 4th case the modem doesn’t power up correctly after pullng down pwrkey for 750ms again.
The effect is similar as described above. If everything is working well we do see expected signals on RX and TX. If the “hang up” happens we do see only high level on RX and TX. We are using direct connection from 1.8V MCU GPIOs with 115k2 Baud.
Is there a workaround and a technical explanation? On the eval boards we don’t see this issue.
Best regards,
Olli