ARINC 429, test case #3
In the two previous articles dedicated to ARINC 429, there are all the necessary concepts to implement functional tests using the ARINC Channels library.
But now, to finish the job, I need the electrical test. Let’s see how to do in this article.
To give the right importance at the electrical test, think about driving a car. You turn the key, start the engine, change into first and go, speed up, brake, steer in both directions: it seems work (PASS functional test), what I have to check anymore?
Much more, for example the pressure of tyres or the engine oil level. Here, the electrical test should be compared to verify the accuracy of some “internal” parameters which ansence although it doesn’t compromise the functionality, degrades the performance.
To carry out some electrical measurements on the Bus ARINC I need three things:
- That the UUT transmits some label, even one.
- That the signal is routed to an oscilloscope (two channels, H and L).
- That it has dreamTest and the ARINC Channels library (the library, for the functional tests, doesn’t need dreamTest; for the electrical test, it uses the oscilloscope functions made available to dreamTest.
Here, a rapresentation of ARINC signal:
From the acquisition in the figure, it was “photographed” the transmission of four labels. I zoom in twice to visualize the transmission of a single label and what kind of electrical measurements are required.
The measures which you are interested about are:
- High, low and resting levels
- period and half-period
- rise and fall times
The sixth function, makes all these measures for you. The parameters to insert are:
- nick: “nickname” gave to the ARINC channel
- channelH: oscilloscope channel, used to acquire the H signal
- channelL: as before, for the L signal
- timeConfig: good default parameters
- channelConfig: as timeConfig.
- method: offers the capability to arm the oscilloscope and then, in a second time carry out the measurement or make both functions in a single call.
- name: is the name that you want to give to the acquisition in order to save it on the disk; empty string to not save (the images proposed in this article, were produced using this).
We open TestStand and we start to write the sequence.
In this figure, we get the part of the sequence in which, for each channel TX to test, are performed the following operations (in the figure, between For and End):
- I route the desired channel towards the oscilloscope
- I enable the UUT to transmit “something”
- I wait
- I call the measurement function just exposed (highlighted in the figure)
- I reopen the channel used for the routing towards the oscilloscope
With this, I really concluded ARINC 429 argument and I give you appointment to the next series of articles (I will talk about 1553).
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Thank you for your time and see you soon with the 1553. I will wait for you to the next article
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