LoRaWAN FUOTA - MIC fail

Question

Hi,
During the fuota process as soon as the fuota session starts i.e. when the firmware fragments are sent from AWS to the end node, I face MIC fail error "**lorawan: McpsIndication failed : MIC fail**" at the end node. I checked the deveui, appkey, joineui are same as in end node and AWS console.I have done successful fuota updates already using AWS but suddenly this error pops out ?
 
**What could be the possible reasons for this error ?**

Thanks.

Greg · Answer

Hi. MIC = Message Integrity Code. It's essentially a checksum performed over the MAC header and MAC payload of your message, and then compared with the MIC In the message. Given that AWS IoT Core LoRaWAN works with lots of devices, it's improbable that it's sending an incorrect MIC. It's more likely that your device has some problem with the MIC calculation.

Have you changed your fragment size? What region are you operating in? It's likely that the FUOTA fragments are the largest payload your device has to deal with, so I would suspect that the MIC failure is related to the large payload size.

LoRaWAN FUOTA - MIC fail

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