I've just...
 

日本に来たばかり。。。日本に来たところだ
According to my books, both form are used to convey the idea of something just happened. Is there a difference or they are synonimous?

There's a difference (or, rather, a couple).

http://nihongo-online.jp/tree02/tree...ako=1&log=6752 explains it well, along with the follow up posts.

I. Short time span: difference
たばかり is a shorter time span that has passed than たところ. For example, 駅に着いたばかりだ is a bit like "I just arrived at the station [and am literally walking around carrying my bags having just gotten off the train]." 駅に着いたところだ could be more like you've just arrived, have found a place to sit, and have gotten out your map to plan where to go from there.

A response to the link above has explained this difference as:
ばかり：*gets off train* I just arrived!
ところ：*gets off train* I just arrived, *wonders what to do next* (次には...)

A little more time for thought/reflection has passed for ところ than ばかり.

II. Long time span: Speaker's feeling
Furthermore, たばかり can have had a lot longer time pass so long as it still feels like a short period of time to the speaker. (kind of related to the lack of ability to reflect, as mentioned in part I above)

For example, if you just got married six months ago, and you're amazed at how fast time is going, 六ヶ月に結婚したばかりなので、まだ新婚者だ is possible. Using ところ there would be wrong.

On a side note, it's amazing how easy it is to easily get grammar questions answered via Google now that I can read upwards of 1500 kanji!

１．日本に来たばかりだ
２．日本に来たところだ

There is a difference. Saying #2 can be totally inappropriate depending the situation.

The key factor from the native speaker's perspective is this: "How long is your intended stay?"

If it's a week, you can say either one during the first day or two. Here, the difference is minimal to non-existent. The two expressions are interchangeable. However, on Day 3 or 4, neither one would sound proper.

If it's a year, while #2 can only be said during the first few days, #1 can be said for as long as a few weeks from your arrival.

To answer your original question, the two are pretty much synonymous but not always interchangeable.

Thanks. That comports with what I said above, and makes me feel more confident in my guessplanation.

Thank you very much. So, by what I understood the difference is only in presence of long period of times. While if I am in front of situation like "I just called him...", "I have just come back home...", "I have just eaten..." it doesn't make a real big difference on which 1 I use. Then I guess it is up to a native speaker to hear what sounds more natural per each situation.

The difference, if I look for one, is that the phrase using ばかり often either implies or be followed immediately by a negative comment whereas ところ is more neutral.

今家に帰ったばかりなので（まだ手紙を読んでいない） 。

昨日ダラスに着いたばかりで、（右も左も分からない） 。

１時間前にご飯を食べたばかりなので、（このサンドイ ッチは食べられません）。

ばかり is like a negative counterpart of だけ to begin with.

Thank you. You explained me things that I didn't know and that can't be found in book :) Appreciate.