From 2c1bba5a518a0907fe7d23f00501284d4e1bb356 Mon Sep 17 00:00:00 2001 From: Joe Foley Date: Tue, 30 Jun 2026 18:00:28 +0000 Subject: [PATCH] discussion on the IMU --- imu.md | 13 +++++++++++++ 1 file changed, 13 insertions(+) create mode 100644 imu.md diff --git a/imu.md b/imu.md new file mode 100644 index 0000000..74efd54 --- /dev/null +++ b/imu.md @@ -0,0 +1,13 @@ +# The Intertial Measurement Unit + +As of 2025, we started using an AliExpress version of https://wolles-elektronikkiste.de/en/icm-20948-9-axis-sensor-part-i + +This has an unmarked jumper on the back. Joe believes that it shorts the VDDIO and VDD pins in order to allow it to be used with 1.8V devices. + +Marcel has tested that the pads connect to both of those pins. + +The IMU runs on 1.8V, but our Pi has GPIO voltages of 3.3V. Marcel reports that students in 2025 had no problem using it as long as AD0 and NCS were connected to VDD. +According to the specification, the maximum pin voltage is VDDIO+0.5, which would put it at 2.3, a whole volt below 3.3. On his board, he connected the pins to 3.3V though a 10K resistor to protect it from overcurrent. + +For I2C at least, it appears that we are saved by the fact that it is open-drain. Each device communicates to the master by pulling lines low, which should work with both voltages. +