Ghost on the Bus

SPI MISO Always High Debug

Symptom

Both reads print 0xFF. The scope shows both reads on SCK and MOSI. MISO never leaves high. The registers and bit fields are on the Datasheet tab.

Circuit

Pass condition

USART1 prints the sensor's two values, one line each: WHO_AM_I:0x<id> then PWR_MGMT_1:0x<value>.

Notes

The bench runs the IMU on SPI1 from power-up: mode 0, up to 1 MHz. A read sends 0x80 | address. The value comes back on the next byte.