SPI master netos

I am having problems implementing SPI on a Connect EM module. I have set port 1 to use the spi driver in the bsp.h file, and have made calls to NASpiRegisterDevice() and NASpiReadWrite(). The CLK & DOUT signals are both present when I send data, but their rise-times are ~500nsec, well out of spec for SPI. I am using the EM dev board as target hardware, and NetOS 6.2 with Multi 4.0

We fought the same battle last year with the EM module. The CPU itself can handle something like 8MHz SPI, but the “problem” is there are external RC filters (which I think also are used to provide the 5v-tolerant inputs) that limit the SPI speed greatly. It works, just really slow.

Biggest problem is this is not documented anywhere, and took a lot of measuring and support emails to finally ascertain.


Those RC filters are the cause, as you said. I removed the caps from the module (not a practical production solution !) and that squared up the waveforms considerably, to the point wher my SPI slave device (a Maxim RTC) would respond reliably to reads & writes. I may have to add a schmitt trigger gate to the outputs to clean up the CLK & MOSI signals.