I hope someone could advise met. I’m interfacing with an SIM800C module using an STM32L MCU. My problem is this: I’m trying to publish data to cloudmqtt using the SIM800C. I’m constructing the entire MQTT packet in firmware and in essence it seems to be working. I ensure that the connect and publish packets are correctly constructed, but I cannot see data arriving on cloudmqtt. Here’s the catch…I fill the actual data array that I want to send with zeros (I add 0xAA and the beginning and end of the array, but the rest is zeros) and then everything seems to be working - I can see data arrive. As soon as I replace the zeros with actual values, the publising fails.
Note that I change NOTHING else, I only forge the actual data part that I want to send by replacing with zeros with actual values incremented from 1. All the other mqtt parameters (remaining lenght etc.) stays the same.
I thought it could be something to do with voltage levels or even the baud rate that is off between the two devices.
I thought I would take a chance here and that maybe someone had some experience.
Thanks in advance!