IMU Driver Implementation

crates/common-arm/src/drivers/IIM20670DriverSpecs.md

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+# IIM20670 Driver Specifications
+
+This document outlines the necessary specifications extracted from the datasheet (DS-000183 Rev 1.0) and reference driver implementation for developing a Rust driver for the IIM-20670 6‑axis IMU sensor.
+
+## 1. General Information
+
+* **Device:** IIM-20670 SmartIndustrial™ 6‑axis MotionTracking® MEMS Device
+* **Key Features:**
+
+  * 3‑axis gyroscope (±41 dps…±1966 dps) with 16‑bit ADC
+  * 3‑axis accelerometer (±2 g…±65 g) with 16‑bit ADC, high‑/low‑resolution modes
+  * Dual temperature sensors
+  * Programmable digital filters per axis
+  * CRC‑protected SPI communication
+* **Package:** 24‑pin DQFN (4.5 × 4.5 × 1.1 mm)
+* **Operating Temperature:** –40 °C…+105 °C
+* **Shock Tolerance:** 10 000 g
+
+## 2. Electrical Characteristics (Driver‑Relevant)
+
+| Parameter             | Min   | Typ     | Max   | Notes                  |
+| --------------------- | ----- | ------- | ----- | ---------------------- |
+| VDD                   | 3.0 V | —       | 5.5 V | Supply voltage         |
+| VDDIO                 | 3.0 V | —       | 5.5 V | I/O supply voltage     |
+| Supply Current        | —     | < 10 mA | —     | All operating modes    |
+| Peak Supply Current   | —     | —       | —     | During ADC conversions |
+| GPIO Drive Capability | —     | —       | —     | Standard CMOS          |
+
+## 3. Communication Interface
+
+### 3.1 SPI
+
+* **Mode:** SPI Mode 0 (CPOL=0, CPHA=0)
+* **Max Clock:** 10 MHz
+* **Frame Format:** 32‑bit (8‑bit command + 16‑bit data + 8‑bit CRC)
+* **Data Order:** MSB first
+* **Pins:**
+
+  * **SCLK** – Serial clock
+  * **MOSI** – Master Out, Slave In
+  * **MISO** – Master In, Slave Out
+  * **NCS**  – Chip Select (active low)
+
+### 3.2 Bank‑Based Register Access
+
+* **Bank 0:** Sensor data & filter registers
+* **Banks 1–7:** Configuration registers (unlock with sequence 0x0002→0x0001→0x0004 to MODE register)
+* **Bank Switch Delay:** ≥100 µs after writing BANK\_SELECT register
+
+## 4. Register Commands
+
+| Name                | Bank | Address | Description                          |
+| ------------------- | ---- | ------- | ------------------------------------ |
+| GYRO\_X\_DATA       | 0    | 0x00    | Raw gyroscope X-axis (16 bits)       |
+| GYRO\_Y\_DATA       | 0    | 0x01    | Raw gyroscope Y-axis                 |
+| GYRO\_Z\_DATA       | 0    | 0x02    | Raw gyroscope Z-axis                 |
+| TEMP1\_DATA         | 0    | 0x03    | Temperature sensor 1                 |
+| ACCEL\_X\_DATA      | 0    | 0x04    | Raw accelerometer X-axis             |
+| ACCEL\_Y\_DATA      | 0    | 0x05    | Raw accelerometer Y-axis             |
+| ACCEL\_Z\_DATA      | 0    | 0x06    | Raw accelerometer Z-axis             |
+| TEMP2\_DATA         | 0    | 0x07    | Temperature sensor 2                 |
+| ACCEL\_X\_DATA\_LR  | 0    | 0x08    | Low-resolution accel X-axis          |
+| ACCEL\_Y\_DATA\_LR  | 0    | 0x09    | Low-resolution accel Y-axis          |
+| ACCEL\_Z\_DATA\_LR  | 0    | 0x0A    | Low-resolution accel Z-axis          |
+| FIXED\_VALUE        | 0    | 0x0B    | Read-back constant (0xAA55 expected) |
+| FILTER\_Y\_Z        | 0    | 0x0C    | Y/Z axis filter configuration        |
+| FILTER\_X           | 0    | 0x0E    | X-axis filter configuration          |
+| TEMP12\_DELTA       | 0    | 0x0F    | Temperature difference (Temp1–Temp2) |
+| RESET\_CONTROL      | 0    | 0x18    | Soft/hard reset commands             |
+| MODE                | 0    | 0x19    | Mode control and lock bits           |
+| BANK\_SELECT        | —    | 0x1F    | Bank selection                       |
+| EN\_ACCEL\_SELFTEST | 7    | 0x11    | Enable accelerometer self-test       |
+| EN\_GYRO\_SELFTEST  | 7    | 0x12    | Enable gyroscope self-test           |
+| ACCEL\_FS\_SEL      | 6    | 0x14    | Accelerometer full-scale selection   |
+| GYRO\_FS\_SEL       | 7    | 0x15    | Gyroscope full-scale selection       |
+| SELF\_TEST          | 7    | 0x16    | Self-test status                     |
+
+## 5. Filter Configuration
+
+Nine cutoff options: 10, 12.5, 27, 30, 46, 60, 250, 300, 400 Hz.  See datasheet Table 14–16 and driver `encode_filter_bits_x` / `encode_filter_bits_yz` implementations.
+
+## 6. Full‑Scale Selection
+
+| Sensor        | Bank | Reg            | Bits   | Range Options (LSB/unit)          |
+| ------------- | ---- | -------------- | ------ | --------------------------------- |
+| Gyroscope     | 7    | GYRO\_FS\_SEL  | \[3:0] | ±41…±1966 dps (800…16.67 LSB/dps) |
+| Accelerometer | 6    | ACCEL\_FS\_SEL | \[2:0] | ±2…±65 g (16000…500 LSB/g)        |
+
+* Defaults: ±655 dps, ±16 g
+
+## 7. CRC & Status
+
+* **CRC‑8**: polynomial 0x1D, init 0xFF, final = bitwise NOT (§5.2)
+* **Status bits**: RS1\:RS0 = bits 1–0 of first MISO byte
+
+  * `01` = OK, `10` = in progress, `00/11` = error (Table 13)
+
+## 8. Initialization & Integrity Check
+
+1. Power-on → NCS high → delay ≥10 ms
+2. Soft reset (`RESET_CONTROL = 0x0002`) → delay ≥200 ms
+3. (Optional hard reset) → delay ≥3 ms
+4. Verify `WHO_AM_I` = 0xF3; `FIXED_VALUE` = 0xAA55
+5. Configure full-scale & filters → lock writes (MODE bit)
+
+## 9. Data Read Sequence
+
+```text
+set_bank(0)
+gx = read_register(0x00)
+gy = read_register(0x01)
+gz = read_register(0x02)
+temp = read_register(0x03)
+ax = read_register(0x04)
+ay = read_register(0x05)
+az = read_register(0x06)
+```
+
+* Convert raw → units:
+
+  * Gyro (dps)  = raw / sensitivity
+  * Accel (g)  = raw / sensitivity
+  * Temp (°C)  = 25.0 + raw/20.0
+  * ΔT (°C)    = raw\_delta/20.0
+
+## 10. Timing Requirements
+
+| Operation          | Delay   |
+| ------------------ | ------- |
+| Bank switch        | ≥100 µs |
+| Soft reset → ready | ≥200 ms |
+| Hard reset → ready | ≥3 ms   |
+
+## 11. Pin Summary
+
+| Pin  | Name | Type | Function                 |
+| ---- | ---- | ---- | ------------------------ |
+| 1    | VDD  | PWR  | 3.0–5.5 V supply         |
+| 2    | GND  | PWR  | Ground                   |
+| 3    | SCLK | I/O  | SPI clock                |
+| 4    | MOSI | I    | SPI data in              |
+| 5    | MISO | O    | SPI data out             |
+| 6    | NCS  | I    | Chip select (active low) |
+| 7–24 | NC   | —    | No connect               |
+
+## 12. Hardware Notes
+
+* Place 100 nF decoupling capacitor close to VDD→GND
+* Keep NCS high between transfers to avoid CRC errors
+* Use self-test bits and check `SELF_TEST` status for diagnostics
+
+## 13. References
+
+* DS‑000183 Rev 1.0 — IIM‑20670 Datasheet
+
+  * Section 4: Data conversion formulas
+  * Section 5.2 & Table 13: CRC & status bits
+  * Section 6.6–6.8: Sensor data & filters
+  * Section 6.12–6.17: Reset, mode, FS selection
+  * Table 14–16: Digital filter descriptions
+  * Table 17–18: Full-scale settings
+
+*Prepared based on driver implementation and IIM-20670 datasheet.*