Originally Posted by MatzeMatz
BTW, the only cables which I found which for sure will work, cost more than 20$/ EUR and that's really expensive!
Same here in USA: digikey $25 + $5 shipping (USD).
The problem is that you can easily search for a 5v or 3.3v adapter, but try searching for a 1.8v adapter and any useful results are buried under a deluge of hits for 6 ft (1.8 m) adapter cables.
The only easy way to find one is from a local distributor, and that is a LOT more expensive than from a Chinese eBay store (where some 3.3v adapters cost under $3 USD, free shipping). That is WHY a level shifter circuit is useful.