Revolution Pi Compact FAQ

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We noticed that when we power up the Revolution Pi Compact, all 8 DIGITAL OUT pins switch to HI for a brief period, perhaps 5-10ms. This happens during every boot. What can I do?

Yes, this is unfortunately a known issue. We are currently working on this bug. Unfortunately, we can't influence the behaviour. The output pins on the Compact come directly from the compute module, and we have no influence on this behaviour at boot time.

• https://revolutionpi.de/forum/viewtopic.php?f=3&t=3329&p=12027#p12027

What is the XXX chip used to multiplex analogue to digital conversions (item 2)?

I have found the following from various specs, etc:

1. DAC is a Dual channel DAC082S085 chip connected to SPI0 of the Raspberry Pi

2. ADC is multiplexed from an XXX chip (I assume on SPI1)

3. Digital I/O is via the GPIO pins (GPIO00 - GPIO27).

Answer:

• The multiplexer: DG408LE

• the selection of the analog input is done via GPIO6, GPIO12 and GPIO13

How can I access the Digital Inputs / Outputs from Codesys?

There is a tutorial which describes the "blinking lights" using Codesys

• https://revolutionpi.com/tutorials/beispiel-blinking-light-2/

I want to count rising edges with the Revolution Pi Compact module, is that possible?

Yes, look here:

• https://revolutionpi.de/forum/viewtopic.php?f=8&t=3062#p11153

What is the sampling rate or cycle time of the analogue inputs?

There is a discussion in the forum here, but it is in German

Finally, the sampling rate is one second with piControl.

Higher sampling rates are possible without piControl

General information about the analogue inputs and outputs:

Tutorials on the topic with and without piControl

I want to read out an analog PNP sensor with Python – how can I do that?

Have a look at this tutorial:

Have a look at the BitMirror example:

The original discussion is here:

Can the digital inputs work as counters?

No, this is not an integrated function of the Revolution Pi Compact.

Can the digital outputs be used for PWM?

No, this is not an integrated function of the Revolution Pi Compact.

I want to connect RS-485 to PLC by I/O RS-485 at Pin P and N (not USB), what do I have to do?

Have a look at our tutorial

There are two different supply voltages – device and IO channels. Is there a sequence to be observed?

• No, the sequence is not relevant. However, external devices should only be connected in a de-energized state and checked for correct wiring before commissioning to avoid destruction.

• Connecting power supply (Compact) - Industrial Raspberry Pi

• Digital Inputs and Outputs (Compact) - Industrial Raspberry Pi

I want to set a GPIO pin high and I don't use piControl. Why does the pin always go low?

• The digital outputs are equipped with a watchdog. A watchdog is a component that monitors the functioning of other components in a system. In this case, the digital outputs must be rewritten at least every 9 milliseconds. If this does not happen, the watchdog sets the digital outputs to “low” to establish a safe state! As the system might have crashed.

There is an undocumented interface on the Revolution Pi Compact, can this be?

The HDMI interface is present but is not considered a warranted capability; therefore we do not warrant or support the HDMI interface.

Can the Revolution Pi Compact be expanded, e.g. with I/O modules?

No, the Revolution Pi Compact is not expandable.

Can the Revolution Pi Compact handle measurements of negative Voltages?

No, the range is 0 - 10 V.

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