SPI connector difference JeeNode <-> JeeNode Micro
Looking at the SPI connector on a JeeNode and a JeeNode Micro, they differ a bit:
1 = SDI RFM12B, MISO ATTINY
4 = SDO RFM12B, MOSI ATTINY
1 = SDO RFM12B, MISO ATMEGA
4 = SDI RFM12B, MOSI ATMEGA
I was just curious what is the reason for this discrepancy.
(@JCW: Thanks for running this very interesting web blog.)
Take a look to the AppNote from Atmel, Figure 7:
With an Attiny, the SPI is implemented through the USI Interface. When configured as SPI Master, the DO Pin (Data Out, PA5) has to be connected to SDI (Slave Data In) on the RFM12 Side.
I guess you have to ignore the usual MOSI / MISO Naming at the Tiny, and think of Data out / Data in here, as visualized in Figure 7.
Maybe someone can validate this, because it is quite confusing….
Correct. There is a blog reference somewhere to exactly this - reversing the sense of the pin naming convention since the implication is that the ‘baby’ ATtiny is always ‘slave’.