Hello,
when we use Verdin IMX8MP Q 4GBIT V1.1A, some of our boards don’t boot.
We tracked the problem down to battery charging. First of all, we have
&rtc_i2c {
aux-voltage-chargeable = <1>;
status = "okay";
};
in our BSP. Disabling the aux-voltage-chargeable = <1>; line “resolves” the problem, but we need the charging.
This is our battery circuit:
We did some measurements, also on the verdin module itself. This is a schematic taken from Verdin datasheet:
We measured that in the failed state, CTRL_RESET_MOCI is down, POR_B (pin on PMIC) is down, JTAG_1_TRST (which is floating on carrier board) is down as well. We were also able to verify that the PMIC chip is fully initialized (by reading its STATUS2 register using external I2C adaptor).
When we desoldered our battery, problem disappeared. Also when I leave the device in the failed state for some time, the device boots.
It all points to a conclusion that when the battery is low (below cca 2.6V), RX8130 pulls down its /RST pin and resets the board until battery is charged. However, according to RX8130 datasheet, the /RST pin should only be pulled down when VDD is low, not VBAT.
Is there something wrong with our setup? If not, how can we deal with discharged battery?
EDIT: I forgot to mention that “Verdin IMX8MP Q 4GB WB IT V1.0C” does not behave like this. When we replace the failing 1.1 Verdin by 1.0 Verdin, the 1.0 Verdin boots without any problem.
