Some other reviews say these units don't work and that was my first impression too. The units appeared to be of high quality, so I found the issues strange and checked them out. After some digging and testing, I found out that the reason for this is that there are resistors on the SPI line (presumably to protect against misconnections) that cause the SPI signals to be smoothed at the expense of line capacitance. This was especially noticeable with the long connecting wires I used in prototyping. After lowering the SPI speed, these devices worked fine even with long connection cables and had a long range. They may have provided a schematic or otherwise communicated that these resistors are installed in the SPI lines. These devices work great, so it's sad to see they get bad reviews just for lack of information.
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