In the previous article, I described the ARINC 429 and explained how to receive the labels transmitted by the unit under test (I recommend reading them to those who have not yet done so).

In this one, I will explain how to transmit the labels, which is necessary to verify that the UUT is able to receive correctly. Remember that ARINC library has six functions: we have already seen three of them and we will use here the other two (for the sixth and last, we have to wait for the next article).

Last time, I deliberately omitted the Hardware configuration. To communicate with our UUT via ARINC you need a PC in which is installed and configured an ARINC card. There are several of them on the market; the ones I worked with are AIM and AIT; make and model do not matter, the "my" library is disconnected from the used card (or almost) and the functions to use in automatic sequence are always the same.

I fly over the configuration steps and resume from the point where I have already written the automatic sequence part that activates the UUT reception.
As in the previous article, I have to set the desired speed and clean the buffer.

To broadcast from the ARINC channel, one or more labels, I have to use the "labelAdd" function, as many times as the desired labels.

The function has only two input parameters: nickname (the nickname used in configuration) and label.
The latter is a structure as follows:

• label: is the label identifier to be transmitted

• SDI: is the SDI of the label to be transmitted

• value: value: the value with which the label will be transmitted, tainted value

• rate: the transmission period, in milliseconds

Sometimes, the test requires to vary the value of the transmitted label and verify that the UUT receives the new data correctly. In this case, I will use a function very similar but conceptually different: “labelWrite”. The previous one has the purpose to add a label in the transmitted lot of label; this modifies the value of a label already present in the same lot.

The function has only input parameters, very similar to the previous one but not equal. The difference lies in the lack of the rate parameter (I cannot change, in running, the transmission period).

I write everything in test sequence, using National Instrument TestStand. I enter the step of type Action in order to add the demanded label (through the function "labelAdd"), to upstream of the verification of the reception from part of the UUT.

But also for the labels in transmission can I use interactivity? Of course. It is availale a panel where all the broadcast labels are listed and where I can add new ones or modify existing ones. I mean, if it helps, I can do the manual test.

With this, I think I have concluded the overview on the codestep of the library dreamTest for ARINC, dedicated to functional tests. It may seem strange, covering almost all ARINC tests with only five codesteps. I assure you that it is true and there is evidence in several test sequences already developed.

It remains to do the electric test (the sixth and last function). For this, I will meet you at the next article.

If you find this article interesting, leave your like. If you have any questions or comments, write to me: I will be happy to answer to all of you.

Thank you for your reading and share if you want.

Antonio Costantino