UART_1 Communication Issue on Dahlia Carrier Board V1.1 with Verdin i.MX8MP

Technical Support
1

I am having trouble getting the UART_1 (Primary UART) to work on my Dahlia Carrier Board V1.1 with Verdin i.MX8MP module. I am trying to communicate with a PC (Linux/Windows) via a USB-to-TTL adapter but no data is being received/transmitted. Is it really impossible to send and receive data when using a 3.3 V USB TTL serial monitor?

2

Hi, I’m the Toradex AI Assistant.

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

The UART_1 interface on the Dahlia Carrier Board can work with a 3.3V USB-to-TTL adapter, but there are specific configuration requirements you need to address.

Hardware Configuration

According to the Dahlia Carrier Board V1.1 Datasheet, UART1 is connected to the primary extension header (1). The Dahlia board features 4 UART interfaces with specific routing (1):

  • UART1: connected to the primary extension header
  • UART2: connected to the second extension header
  • UART3: connected to built-in USB to Serial transceiver (Debug interface)
  • UART4: connected to built-in USB to Serial transceiver (Debug interface)

Voltage Level Considerations

The key issue you’re experiencing is likely related to voltage levels. The Verdin i.MX8MP operates with 1.8V I/O levels, while your USB-to-TTL adapter uses 3.3V (2). This voltage mismatch can prevent proper communication.

Serial Parameters

When configuring your connection, ensure you’re using the correct serial parameters (2):

  • Baud Rate: 115200
  • Parity: none
  • Bits: 8
  • Stop bits: 1
  • Flow control: none

Recommended Solutions

Option 1: Use the Built-in Debug Interface

The easiest solution is to use the built-in USB to Serial converter on the Dahlia board. Connect a USB-C to USB Type-A cable to the DEBUG connector (X18) (2). This provides direct access to UART3, which serves as the primary debug console.

Option 2: Level Shifting for UART1

If you specifically need UART1, you’ll need to add level shifting circuitry between the 1.8V Verdin signals and your 3.3V USB-to-TTL adapter. The voltage mismatch is preventing proper signal recognition.

Option 3: Use 1.8V Compatible Adapter

Consider using a USB-to-TTL adapter that supports 1.8V operation, or one with adjustable voltage levels.

Verification Steps

  1. First, test with the built-in debug interface (X18 connector) to confirm your setup works
  2. Check that your device appears correctly in Linux (/dev/ttyUSB*) or Windows (Device Manager)
  3. Verify the correct serial port parameters are configured

The issue is not that it’s impossible to use UART1 with a 3.3V adapter, but rather that proper level shifting is required due to the voltage difference between the Verdin module (1.8V) and your adapter (3.3V).

Best regards, Toradex AI Assistant.

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