Verdin iMX8M Mini – RS485 RX issues and SC16IS762 IRQ instability on custom carrier board

Technical Support
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Hi, I’m the Toradex AI Assistant.

I might make mistakes or occasionally get you wrong. Our support team will step in if needed.

I’d be glad to help with your RS485 and SC16IS762 issues! To provide the most accurate guidance, could you let me know which OS and version you are running on your Verdin iMX8M Mini? For example:

  • Hardware: Verdin iMX8M Mini Quad 2GB Wi-Fi / Bluetooth IT (No CAN) V1.1A
  • OS: Torizon OS 6.8.2, Torizon OS 7.2.0-build.13, Yocto BSP 7, etc.

You can get detailed information about your setup using the tdx-info command - see this guide for more details.

Initial Analysis of Your Issues

Based on the information provided, I can see you’re experiencing:

  1. RS485 RX corruption despite working TX
  2. SC16IS762 interrupt storm causing high CPU usage

RS485 Configuration Insights

From the community discussion on a similar setup (1), there are some key considerations for RS485 on Verdin iMX8M Mini:

Device Tree RS485 Settings

For proper RS485 operation, the device tree configuration should include proper direction control (1):

&uart3 {
    status = "okay";
    linux,rs485-enabled-at-boot-time;
    rs485-rts-active-low; // Adjust polarity as required by your board
    // Remove rs485-rx-during-tx; to suppress echo
};

Echo Suppression

The documentation indicates that RS485 can echo transmissions if the transceiver’s receive line is enabled during transmission (1). The rs485-rx-during-tx property should be removed unless you specifically need to receive while transmitting, as this enables loopback (echo) (1).

Device Tree Overlay Considerations

When working with custom pin configurations, the device tree overlay approach is recommended (2). Your pin multiplexing configuration needs to ensure:

  1. Proper pin function assignment
  2. Correct pad configuration values
  3. No conflicting peripheral usage

Once you provide your OS version, I can give you more specific guidance on:

  • Proper interrupt configuration for SC16IS762
  • Recommended pad settings for GPIO5_IO3
  • RS485 direction control validation
  • SPI3 configuration specifics for your platform

Best regards, Toradex AI Assistant.

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