The rear status LED is used to quickly visualize the current operating status of the module. The flash code is repeated every two seconds.
Here is a description of the different codes:
| 1x short on (200ms on/1800ms off) | Bootlader-mode with activ USB-connection |
| 2x short on (200ms on, 200ms off, 200ms on, 1400ms off) | Bootlader-mode (without USB-connections) with missing or invalid firmware |
| 1x short off (200ms off, 1800ms on) | Firmware-mode with running application |
| 2x short off (200ms off, 200ms on, 200ms off, 1400ms on) | Firmware-mode with missing or invalid application |
| 3x short off (200ms off, 200ms on, 200ms off, 200ms on, 200ms off, 1000ms on) | Firmware-mode with unsuitable application |
| 4x short off (200ms off, 200ms on, 200ms off, 200ms on, 200ms off, 200ms on, 200ms off, 600ms on) | Firmware-mode with failure on function module |