On the Adafruit website I found a confusing information about the TX and RX characteristics. As it describes here, the RX acts as a transmitter and TX as a receiver.
But in the table above I can see that TX is for writing data and rx for reading.
I thought that TX->RX and RX<-TX is only connection one-directional.
I hope someone can help me with this confusing information.
TX (0x0002) This characteristic is used to send data back to the sensor node, and can be written to by the connected Central device (the mobile phone, tablet, etc.).
RX (0x0003) This characteristic is used to send data out to the connected Central device. Notify can be enabled by the connected device so that an alert is raised every time the TX channel is updated.
TX is abreviation for Transmitter. RX for receiver. These are seen from the Central side. The Central can/should enable notifications on the RX characteristic to get the data and not having to poll.