I am experiencing an issue with my board, where I have interfaced an nRF52840 with an LSM6DSV16 via SPI.
The nRF52840 chip, once started, can decide whether or not to power the LSM6DSV16 (1.8V_SYS in the schematic above) through a signal controlling an LDO. However, I noticed that if I configure SPI in the DTS file by enabling it with status="okay";
&spi0 {
compatible = "nordic,nrf-spim";
status = "okay";
pinctrl-0 = <&spi0_default>;
pinctrl-1 = <&spi0_sleep>;
pinctrl-names = "default", "sleep";
cs-gpios = <&gpio0 7 GPIO_ACTIVE_LOW>;
lsm6dsv16x: lsm6dsv16x@0 {
compatible = "st,lsm6dsv16x";
reg = <0>;
spi-max-frequency = <8000000>;
};
};
spi0_default: spi0_default {
group1 {
psels = <NRF_PSEL(SPIM_SCK, 0, 4)>,
<NRF_PSEL(SPIM_MOSI, 0, 28)>,
<NRF_PSEL(SPIM_MISO, 0, 29)>;
};
};
spi0_sleep: spi0_sleep {
group1 {
psels = <NRF_PSEL(SPIM_SCK, 0, 4)>,
<NRF_PSEL(SPIM_MOSI, 0, 28)>,
<NRF_PSEL(SPIM_MISO, 0, 29)>;
low-power-enable;
};
};
even if I disable the LDO powering the LSM6DSV16, I still have a (return?) voltage on 1.8V_SYS, which is approximately 1.5V/1.7V. If I disable SPI with status="disabled";
&spi0 {
compatible = "nordic,nrf-spim";
status = "disabled";
pinctrl-0 = <&spi0_default>;
pinctrl-1 = <&spi0_sleep>;
pinctrl-names = "default", "sleep";
cs-gpios = <&gpio0 7 GPIO_ACTIVE_LOW>;
lsm6dsv16x: lsm6dsv16x@0 {
compatible = "st,lsm6dsv16x";
reg = <0>;
spi-max-frequency = <8000000>;
};
};
spi0_default: spi0_default {
group1 {
psels = <NRF_PSEL(SPIM_SCK, 0, 4)>,
<NRF_PSEL(SPIM_MOSI, 0, 28)>,
<NRF_PSEL(SPIM_MISO, 0, 29)>;
};
};
spi0_sleep: spi0_sleep {
group1 {
psels = <NRF_PSEL(SPIM_SCK, 0, 4)>,
<NRF_PSEL(SPIM_MOSI, 0, 28)>,
<NRF_PSEL(SPIM_MISO, 0, 29)>;
low-power-enable;
};
};
the issue does not occur, and everything works as expected. At this point, I believe the problem is due to the SPI signal handling by the nRF52840, which somehow passes through the LSM6DSV16 (internal pull-up resistors?).
So, I ask: why am I seeing this behavior, and how can I fix it? Is there a way to modify the peripheral's status at runtime?