RP2040

If the handshake consistently fails, try manually setting the RX pin to INPUT mode before calling begin():

void setup() {
  pinMode(RX_PIN, INPUT);
  device.begin();
}

ATmega328/P

Disable the automatic host type detection feature by defining the LUMP_HOST_DETECT_OFF macro before including the library header:

#define LUMP_HOST_DETECT_OFF
#include <LumpDeviceBuilder.h>

Reason:

During the handshake phase, to perform AutoID, the UART is required to:

• Ground the TX pin to indicate UART mode to the host.
• Enable RX to receive information from the host for automatic host type detection.

To achieve this, the library follows a simple sequence:

1. Initializes the UART.
2. Grounds the TX pin.

However, this sequence may not work on all MCUs due to hardware differences. For example, on the ATmega328/P, register manipulation is required to ground the TX pin after UART initialization.

Therefore, on such MCUs, automatic host type detection must be manually disabled to ensure proper operation.