March 6, 2012
about 3 years ago
Just got mine and forgot to order the shield connectors. So I’m asking this in advance before being able to check it myself and fry the shield. To be honest, I would like to know why wiring pin 7 RESET to RST is necessary at all? But slowly …
I’ve read the comments about wiring the shields pin 7 RESET to Arduino’s RST pin. So far so clear … really? Why is this necessary at all? The datasheet says that the MAX3421E has its own internal POR generator. As far as I could see from Oleg’s sources, all he does is a “soft” reset through the appropriate register accessible via SPI. And this register does not touch SPI communication, as also pin 7 RESET/RST does not.
So what can be the reason for Oleg’s library and QC sketch to fail at all? There has been the (independent) POR and contrary what other wrote here, there is no pulling the Arduino’s RST low as this would also reset the Arduino and restart the QC sketch or whatever. Someone a working explanation?
The Usb::init() method just issues a bmCHIPRES to rUSBCTL, then clears rUSBCTL and waits for bmOSCOKIRQ to become set in rUSBIRQ. There is no fiddling with RST/RESET at all. It just spins and waits for the for the bit to become set.
Any why is there the hardware RESET pin 7 at all if there is the really equivalent bmCHIPRES? Does the latter have issues and is not reliable? But then, the QC should also fail…?
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