SparkFun LTE Stick LARA-R6 Not Responding to UART or USB

Wireless & IoT Cellular
1

I’m unable to get the LARA-R6 module to respond to AT commands via UART or enumerate as a USB device. I’ve tested two different LTE STticks with identical results.

Setup:

  • SparkFun Artemis Thing Plus

  • SparkFun LTE Stick LARA-R6

  • Wiring: Artemis Pin 1 (TX1) → LARA RXD, Pin 0 (RX1) → LARA TXD, VUSB → VIN, GND → GND

  • Power: Via USB-C directly to LARA-R6

  • Code: SparkFun u-blox Cellular Library Example 1

  • Macbook Pro - (Cannot install u-blox m-center)

Troubleshooting completed:

  • Verified Artemis Serial1 working via loopback test

  • Confirmed correct TX/RX crossover wiring with continuity testing

  • Verified all solder jumpers (PWR_LED, ON_LED, DTR) are closed

  • Both PWR and ON LEDs illuminate when powered

  • Tried multiple power-on sequences (tap once, hold 3 seconds to off, etc.)

  • Tested with module powered via both Artemis VUSB and direct USB-C

  • SIM & antenna installed

Result: Module fails autobaud with “Module failed echo test” error. LARA-R6 does not appear as USB device in system. Same behavior on both modules tested.

Any suggestions?

IMG_5089.HEIC
IMG_5089.HEIC3024×4032 3.08 MB

2

If you do a loopback test the LARA by itself does it work?

3

I would be happy to try, however before doing so I tried to run this simple loopback test on my artemis:

void setup() {
Serial.begin(115200);
Serial1.begin(115200);
delay(1000);  // Give Serial1 time to initialize
Serial.println(“Serial1 loopback test starting…”);
}

void loop() {
// Clear any junk in the buffer first
while(Serial1.available()) {
Serial1.read();
}

// Send a single character
Serial1.write(‘A’);
Serial1.flush();  // Wait for transmission to complete

delay(50);  // Give time for loopback

if (Serial1.available() > 0) {
char received = Serial1.read();
Serial.print("SUCCESS! Received: ");
Serial.println(received);
} else {
Serial.println(“FAILED - No data received”);
}

delay(1000);
}

Now it too is failing to receive data, this is the second board that is showing this after connecting it to the TXD and RXD pins on the Lara.

For context, this simple text passed on the fresh artemis, I connected and now failed.

4

Ah, I found something. The LARA is 1.8v Hardware Overview - SparkFun LTE Stick - LARA-R6 Hookup Guide
https://cdn.sparkfun.com/assets/8/9/5/2/1/SparkFun_LTE_Stick_LARA_R6.pdf
and the Artemis is 3.3v, you’ll need a level-shifter to have those chat