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Support Question of the Week: How Can I Use a Single SPI Host Adapter to Control SPI Devices with Different Bitrates and Command Lengths?

I have two different SPI devices and I need to transmit two different command settings. Because of the separate SS (slave select) signal pins, it looks like a Cheetah host adapter should work with this.

The two SPI devices that I intend to control with the Cheetah adapter have different command lengths:

  • SS1 requires a 72-bit command
  • SS2 requires a 24-bit command

The commands will be transmitted one after another, not in parallel. How can I configure this?

Thanks for your question! Having three separate SS signals, the Cheetah SPI Host Adapter can control up to three separate SPI devices Regarding SPI transfer rates, you can transfer SPI data with the Cheetah adapter using the Cheetah GUI Software, the Flash Center Software or the Cheetah Software API.

Use Cheetah SPI Host Adapter and Software to Control SPI Devices with Different Bitrates and Command Lengths Figure 1: Cheetah SPI Host Adapter

Following is a summary of the advantages of each software application:

  • The Cheetah GUI Software provides full access to all Cheetah adapter functionality, and eliminates the need to write custom software to control the adapter.
  • The Flash Center Software provides mechanism to quickly erase, program, and verify SPI based EEPROM and flash memory Chips. It has extensible XML parts library with built-in support for EEPROMs and serial flash chips from major manufacturers.
  • The Cheetah Software API is used to control the adapter, and to write a custom program to achieve the user goals. The API comes with support for multiple OS (Windows, Linux, and Mac) and multiple languages (C, Python, Net, and C#), and includes examples. We recommend using the Python bindings as it is a simple language, and a good option for scripting.

Using one Cheetah GUI, you use (one Cheetah GUI or Cheetah API) instance to connect to the one Cheetah SPI Host Adapter and to the two SPI slave devices.

  1. For the first transmission, the Cheetah adapter (with Cheetah GUI or Cheetah API) can send the first SPI slave a command using a specified packet length with bitrate.
  2. For the second transmission, the Cheetah adapter can send the second SPI slave a command using a different specified packet length and bitrate.

The guidelines are as follows:

  1. Connect the Cheetah adapter to one Cheetah GUI instance.
  2. Configure Cheetah GUI for the appropriate SS signal for the devices: packet size and bitrate

    • SS1, 72 bit packet size
    • SS2, 24 bit packet

For additional information about using the Cheetah adapter with the Cheetah GUI Software, please refer to the knowledge base article Writing and Reading from SPI Flash Using Cheetah Adapter and Cheetah GUI.

For additional information, please refer to the following documents: