@STTwo-32 ,
Since one customer stumbled here (*), I'd like to suggest to ST that you should add a footnote (or an actual step) to the "test procedure" section in AN4494, reminding the user to consult the SPI timing requirements portion of the relevant datasheet, possibly with an explicit exhortation to consider timing for the CS signal (the duration of the CS delay required is surprisingly long at 10 clock cycles).
Though the datasheet does document the timing requirements, it makes good business sense to treat the issues customer raise as a form of feedback about documentation, even (and perhaps especially) when their problem is a result of overlooking something that *is* properly documented somewhere else.
Since AN4494 is designated as THE bring-up document for a entire line of ST products (BlueRNG is now in its 4th gen, I think?), this appnote should be considered as a "funnel" through which most BlueRNG customers are likely to pass through. So, it makes particular sense to optimize this particular section against common problems, as it's likely to have outsize impact.
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