How many SPI devices can I use on a LoPy?

  • I'm looking at using 4x or 5x of these: Thermocouple Amplifier MAX31855 to connect to Type K temp probes. Just wondering if a LoPy would be suitable for the following use case:

    OLED Display with temps shown (button to display and 15 sec timeout to save power)
    MQTT connection over wifi when available
    eventually LoRa once I setup a gateway
    BLE for integration with a smartphone app.

    I saw the LoPy has 2x SPI but as im new to SPI im not sure how it works.. if I use two SPI pins across all boards then a normal digital IO pin per MAX31855 board?

  • @sjp770 SPI is a bus system. In a star configuration you can connect several slave devices to one master, as long as the (capacitive) load is not exceeded. But you need a CS for each device. If D/C is needed, you may be able to share it. If devices have active feedback pins like an Alarm pin, that has to be connected too to a separate I/O.

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