Totally useless, the circuit doesn't have any level switches and can't be used as a 5V to 3.3V SPI interface. It's pretty much just an LDO with a little red LED. It turns the 5V from the Arduino into 3.3V for the transmitter board, but all SPI logic signals are connected 1:1. The MISO is not shifted to 5V, and the main outputs are not shifted to 3.3V.
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