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Can I Modify the SPI Protocol for SS to Create a Signal Between Byte Transmissions?
Rena Ayeras

Image by Gerd Altmann from Pixabay

Question from the Customer:

I have the Aardvark I2C/SPI Host Adapter. I am wondering if there is a way to modify the SPI protocol so that SS (slave select) returns high between bytes during the entire sequence. Right now, SS goes low at the start of a communication and stays low until all bytes have transmitted.

Here is a diagram comparing what the Aardvark adapter currently provides and the Target SS timing that I am looking for:

Response from Technical Support:

Thank you for your question! Our recommendation is to execute individual operations for each byte, which you can do with the Aardvark Software API. However, this may slow down the speed of the original operation. To improve the speed of the performance, we recommend queuing the API commands, which you can do with the Cheetah SPI Host Adapter as well as the Promira Serial Platform.

The Faster Cheetah SPI Host Adapter

The Cheetah SPI Host Adapter actively communicates on the bus, operates at high speeds up to 40+ MHz, offers gapless shifting, and provides control over the timing of the data that is shifted out. This adapter operates with a high-speed USB link. When using the Cheetah adapter's synchronous interface compared to the Aardvark adapter, the USB latency will be reduced from 2ms to about 250us.

There is also an asynchronous interface that could further accelerate the operations. The asynchronous interface supports queuing the data delivered by the Cheetah adapter, which produces gapless shifting.

The API for Cheetah adapter has a different scheme for creating SPI transactions than the Aardvark adapter. For an example of queuing with the asynchronous interface, please refer to Using Cheetah to Send Multiple SPI Packets with One Transfer.

Promira Serial Platform for Advanced SPI Protocol Transmissions

The Promira platform works over Ethernet interface and offers data transmission through a queuing mechanism, which supports data transmissions with minimal delays. Similar to the Aardvark adapter, but with a significantly greater bitrate, the Promira platform can support SPI and I2C protocols. Separate licenses are available for specific levels of speed and functions.

Here is a summary of the Promira Serial Platform features:

  • Integrated level shifting ensures you'll be able to work at a variety of voltages ranging from 0.9 to 5.0 volts without needing any costly accessory boards.
  • High-speed USB connectivity to the host system provides high performance and convenience for benchtop programming, testing, and emulation.
  • Ethernet connectivity is convenient for benchtop work, and it also enables remote control for your automation needs.
  • By providing up to 200 mA of power to target devices, the Promira platform can easily power your projects with simplified connectivity and troubleshooting.

Here is an article that is related to your question: To Run SPI Tests at a Higher Speed, How Do I Set Up Ethernet Connectivity and the Async Queue for the Promira Serial Platform?

We hope this answers your question. Additional resources that you may find helpful include the following:

If you want more information, feel free to contact us with your questions, or request a demo that applies to your application.