I’ve been working on a sample application alterning RX and TX period (TDMA like).
On a sample PCB, powered by USB (with, I assume, sufficient power), then after a while, the consumption traces go haywire.
The current/voltage conversion ratio is 1V = 10mA (I use a 2 ohms sense with a MAX9938 x50 amplifier to have a span fitting my needs, and a Saleae Logic Pro 8 to capture).
The large view, the black shape is the problem:
Closer view, at first only TX periods are hitting ~30mA, and RX periods stay at ~8mA. But after you can see the RX periods reaches the TX consumption levels!
Here is a typical OK consumption RX zoomed period:
Here is a faulty consumption RX zoomed period (I’ve zoomed even more to see the current spikes:
The TX is also affected, here is a clean OK consumption TX period:
And the corresponding faulty TX consumption zoomed period:
Strangely enough, the problem is only transient, but repeats itself. Therefore I guess there is a hardware or IO sequence problem. Has anyone encountered this behavior?
Edit: the spikes within the RX/TX faulty period has a 22644 Hz frequency. The modulation is SF8, BW=800KHz, CR=4/5, frequency is FHSS, and many channels are impacted, regulator is always SMPS+LDO.