master & slave SPI with Duemilanove

Forum 2005-2010 (read only) Hardware Interfacing
1

Hi. I'm a new Arduino user (loving it!!) with heaps of software experience, but just hobby-level electronics experience. Maybe you can help? :slight_smile:

I'm working on a project that needs an Arduino as both SPI master ~and~ SPI slave. I already have the dedicated SPI pins (Arduino 11,12,13) talking back & forth with an external slave at 2Mhz, no problem. But now I need to move this to the UART MSPIM pins (Arduino 0,1,4) and use the Arduino as a slave to another controller on pins 10-13. So I have a couple of questions about the Duemilanove board:

  1. Will the pin 13 LED cause problems with the external master SCK signal?
    The master controller has a max output current of only 2mA per pin. The pin 13 LED will draw more current than that, right? Is there any way to work around this, besides removing the LED from the board?

  2. Will the Serial<>USB chip (FT232RL) cause problems with the Arduino MISO signal on pin 0?
    I understand that all devices on the MISO line except the active slave need to be tri-stated (disconnected). Is there some way to tri-state the TXD pin on the FT232RL chip?

If the answer is "use a different Arduino board with no LED or USB", I'm OK with that. I just want to see if I can use what I have first. Thanks for any help!

2

Maybe I should rephrase these 2 questions...

1) To use the Arduino Duemilanove as an SPI slave (pins 10-13) with a 2mA/pin (maximum) master SCK on pin 13, do I need to disconnect the pin 13 LED?

2) To use the Arduino Duemilanove as an SPI master via UART MSPIM (pins 0,1,4) on the Arduino, do I need to disconnect or find some way to tri-state the TXD of the FT232RL?

Sorry if these are silly questions. :slight_smile: Thanks for any help!