Hi,
I am encountering a strange intermittent problem initializing an AP281M5IB (rev. F) module in byte sync mode. About 90% of the time, the SEN\\ signal from the module never asserts, neither after startup/reset, nor in response to MRDY\\ signal from the host MCU. From what I understand, "normal" operation is for the module to assert SEN\\ immediately after reset, and deliver an 0x6F startup message (which happens, but very rarely).
I've attached a logic analyzer trace showing the issue in more detail. Ohmmeter test between the PCB pins and the vias atop the module indicate all pads are correctly soldered
Note the line labeled 'SSFAKER' is a software-generated signal to the the MCU's hardware SS\\ line (SEN\\ can't be used directly as ANT pulls it high at the start of the last byte, making it lost to the MCU).
Can anyone see a problem, or suggest what might be going on here? Is it possible I just have a broken module?
Thanks!
