I am working on a project that is using an ATtiny861A and this only has one SPI. If I want to hook up a radio and an external memory to the same SPI, will there be an issue sending data from the external memory to the radio? I know I can hook up the external memory and the radio to the same SPI but I am not sure if the radio will be able to send the data saved on the external memory.

  • \$\begingroup\$ Any particular radio? \$\endgroup\$ Commented May 20, 2015 at 14:52
  • \$\begingroup\$ It will be a CC2520 from Texas Instruments \$\endgroup\$ Commented May 21, 2015 at 17:39
  • \$\begingroup\$ I'm fairly sure you could run that as a master, making a multi-master system. \$\endgroup\$ Commented May 21, 2015 at 18:01

1 Answer 1


Your micro is the master and as such you can't get this type of bus to interact slave-to-slave. It's a case of reading the memory into the micro and then forwarding this to the radio i.e. the micro must buffer the data when sending it between slaves.

  • \$\begingroup\$ So they can communicate but the Micro-controller needs to hold the data before it is sent? Would this all be done in the coding? \$\endgroup\$ Commented May 20, 2015 at 14:11
  • \$\begingroup\$ Yes, it is done in the micro's coding \$\endgroup\$
    – Andy aka
    Commented May 20, 2015 at 14:16
  • \$\begingroup\$ @Therusscher SPI being Master-Slave protocol, Everything must go through Master \$\endgroup\$
    – Swanand
    Commented May 21, 2015 at 10:04

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