Fix SPI register masking in busWriteBuf

[sensei-hacker]

User description

Summary

Corrects SPI register address masking in busWriteBuf() to clear the MSB instead of setting it.

Problem

For SPI protocol, the MSB indicates read (1) or write (0) operations. The busWriteBuf() function incorrectly used reg | 0x80 which sets the MSB, when it should use reg & 0x7F to clear it for write operations.

This is inconsistent with the correct implementation in busWrite() at line 318.

Solution

Change line 286 from:

return spiBusWriteBuffer(dev, reg | 0x80, data, length);

To:

return spiBusWriteBuffer(dev, reg & 0x7F, data, length);

Impact

Current hardware: None - all devices using busWriteBuf() are I2C-based (VL53L0X, VL53L1X, MLX90393, TERARANGER_EVO, US42 rangefinders).

Future hardware: Prevents silent failures if SPI devices use multi-byte buffer writes.

This is a defensive fix for code correctness.

Fixes #10674

---

PR Type

Bug fix

---

Description

• Corrects SPI register masking in busWriteBuf() to clear MSB for writes

• Changes register operation from OR (0x80) to AND (0x7F) masking

• Aligns implementation with correct busWrite() function behavior

• Prevents future silent failures in SPI multi-byte buffer writes

---

Diagram Walkthrough

flowchart LR
  A["busWriteBuf SPI path"] --> B["Register masking operation"]
  B --> C["Previous: reg | 0x80 sets MSB"]
  B --> D["Fixed: reg & 0x7F clears MSB"]
  D --> E["Correct write operation"]
  C --> F["Incorrect read operation"]

Loading

File Walkthrough

	Relevant files
Bug fix	bus.c Fix SPI write register masking operation                                  src/main/drivers/bus.c Changed SPI register masking from reg | 0x80 to reg & 0x7F in busWriteBuf() Corrects MSB handling for write operations in SPI protocol Aligns with correct implementation in busWrite() function Affects only theoretical future SPI devices; current devices are I2C-based +1/-1

---

[qodo-code-review]

PR Compliance Guide 🔍

All compliance sections have been disabled in the configurations.

[github-actions]

Branch Targeting Suggestion

You've targeted the master branch with this PR. Please consider if a version branch might be more appropriate:

• maintenance-9.x - If your change is backward-compatible and won't create compatibility issues between INAV firmware and Configurator 9.x versions. This will allow your PR to be included in the next 9.x release.

• maintenance-10.x - If your change introduces compatibility requirements between firmware and configurator that would break 9.x compatibility. This is for PRs which will be included in INAV 10.x

If master is the correct target for this change, no action is needed.

---

This is an automated suggestion to help route contributions to the appropriate branch.

[qodo-code-review]

PR Code Suggestions ✨

No code suggestions found for the PR.