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PaxInstruments / t400-electronics

Electronics for the Pax Instruments T400 temperature datalogger
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SPI bus design #150

Closed charlespax closed 9 years ago

charlespax commented 9 years ago

I'm posting this application note about SPI bus design. I don't think we need this for the T400 thought. Moving to Ice box. http://hackaday.com/2014/11/25/better-spi-bus-design/

samchoy88 commented 9 years ago

It looks great and better design to avoid unexpected failure on SPI bus. But it give extra cost on design.

samchoy88 commented 9 years ago

image

Here are the reference reason of this design.

  1. Add Pullup Resistors for Chip Select & Reset Signals: Without a pullup resistor, the second device can "hear" and respond to the communication taking place on the first device, if that second device's chip select pin is not pulled up.
  2. Verify tri-state behavior on MISO: use a tri-state buffer chip if necessary. Most SPI chips will tri-state (effectively disconnect) their MISO pin when their chip select signal is high (inactive). However, some chips do not have proper MISO tri-state behavior.
  3. Protect bus access with SPI.beginTransaction(settings) and SPI.endTransaction(). Newer versions of Arduino's SPI library support transactions. Transactions give you 2 benefits: -Your SPI settings are used, even if other devices use different settings -Your device gains exclusive use of the SPI bus. Others will not disturb you.
charlespax commented 9 years ago

Will not do. Closing issue.