Meaning of telegraph code in the song "Planetes" The song Planetes in Guilty Crown begins with some telegraph encoding, which I think is Wabun code.
Here is the YouTube link.
My transcription is:
-•-• -••-- •-- --•-- •- --•-• •-•-- -•--•

which decodes to this:

ni-yu-ya a-i-shi-te-ru

Niyuya didn't make sense. Did I get something wrong?
It really is Wabun Code. The telegraph sequence at the start of the song was widely known and had been discussed on Japanese website, all of them says 「集｛しゅう｝　愛｛あい｝してる」 (Shu-u, ai-shi-te-ru) is the encoded message. [1] [2] [3] [4] [5] [6]
If you take a look at the Wikipedia page you cited, the small ゃ ya, ゅ yu, ょ yo in the digraphs are encoded the same as regular や　ya, ゆ yu, よ yo.
So we can comparing your attempt at decoding:
-•-• -••-- •--

and the supposed coding of the message (shi-yu-u):
--•-• -••-- ••-

Listening to the telegraph sequence again to cross-check, while I can agree with Japanese fans' transcription of the 3rd mora ••-, I could only hear 1 dash at the beginning for the first mora --•-•. And apparently, the author of answer [1] on Yahoo also encountered the same problem:

ネタバレになってしまいますが、
「しゅう あいしてる」
だそうです。桜満集のことですね。
ただ、最初の音(？)が微妙に「にゅ」と解読されるようですが、「にゅう あいしてる」だと意味が通じないので「しゅう あいしてる」で間違いないとおもいます。

Translation:

This is going to be a spoiler,
but it seems to be &quot;Shuu, I love you&quot;.
&quot;Shuu&quot; here is referring to Ouma Shuu.
However, although the first sound somewhat decodes to &quot;nyuu&quot;, &quot;nyuu aishiteru&quot; doesn't really make sense, so I think it is definitely &quot;Shuu aishiteru&quot;.

There is this question on Yahoo Answer which says that apart from the Morse code at the beginning and at the end (which I myself also confirm, but I don't bother to decode it), the asker feels that there are also Morse code playing in the background through out the song (which I also feel there is something, but listening closely reveals nothing).