I have 4 of these same flow meters. I used to attach them to the UART version of the FLOW circuit produced by Atlas-Scientific, but that was using an Arduino DUE and the sample code on that site. The newest version of the EZO- FLO circuit supports i2c,but it does costs $40, which is a bit of money to spend to read a $10 flow meter.
I have a different flow meter in use at the moment attached to the EZO-FLO i2c circuit. However, in the coming weeks, I will configure the EZO-FLOW i2c circuit for the Yf-s201... I've downloaded the specs for it, but it's on a different computer so I can't provide them to you for a few days... You can search for them yourself .
I'm a big fan of the EZO-FLO i2c circuit because totalization and instantaneous flow using pulse counts is a bit CPU intensive..... With the EZO-FLO circuit you are offloading all of that.... Then you can just have your flow talk to the EZO-FLO using the Node-RED-contrib-i2c node.
This thread here has the flow used (though disabled...but it works when I hook it up).
