How Can the Promira Serial Platform's GPIO be Used as Data Lines for non-SPI Devices?

Question from the Customer:
We’re considering purchasing the Promira Serial Platform with SPI Active - Level 1 Application. We like the USB connectivity, Labview support, and adjustable voltage features - now we have some questions about GPIO.

  • Can we use GPIOs on Promira as data lines?
  • Our application is not SPI; we are looking for one CLK output and 5 or 6 Data outputs synchronized by the CLK.
  • With SPI Active - Level 1, one transaction is 1Mbits per output data line

Response from Technical Support:
Thanks for your questions! Using the Promira Software API, you can manually generate a clock. A separate clock is not provided for GPIO. To manually set the clock simply use the Promira Software API command ps_queue_gpio_set(): toggle the pin with 0 and 1 to create clock pulses. The speed of the clock depends upon the end user system's execution speed.  Here is an example of generating a clock with a 50% duty cycle:

  1. ps_queue_gpio_set(queue, STATE0)
  2. ps_queue_delay_ms(queue, on_time_in_ms)
  3. ps_queue_gpio_set(queue, STATE1)
  4. ps_queue_delay_ms(queue, off_time_in_ms)

Repeating that series of time will generate the clock pulses. For a  50% duty cycle, on_time_in_ms = off_time_in_ms.

The STATE0 and STATE1 parameters are set in terms of bitmasks of the available GPIOs. With Promira  configured with SPI level 1, you can use up to 6 GPIOs [pin 1, 3, 9, 14, 15, 17] (or 2 GPIOs [pin 1, 3] when SPI is configured in your code simultaneously)

Please note, there are speed limitations. The switching speed of GPIO pins depends on the time of the line-by-line execution of your script. The overhead of the Operating System may add to the delay. There is also a latency caused by the Ethernet/USB link between the computer and the Promira platform.

The bitrates set for SPI/I2C has no effect on the GPIO pin switching.

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

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