3.3 Signal Timing

The following figure illustrates the signal timing of the data transfer.

  1. The remote sensor transmits a data telegram with duration of 11 ms every 10s or when the user presses the SW1 or the SW2 button (TX1). The preamble duration is 7 ms while the data payload duration is 4 ms. Then, the remote sensor switches into Receive mode with a time-out period of 20 ms (RX).
  2. The base station is polling for a valid RF signal that matches the RF channel, the data rate, the modulation scheme and the correct data encoding every 5 ms. This polling interval is chosen to match with the length of the preamble. When the base station receives a valid telegram (RX1), it acknowledges this telegram (TX) and waits for an acknowledgment frame from the remote sensor with the Remote Sensor signal strength data and a time-out of 90 ms (RX2).
  3. The remote sensor transmits the acknowledgment frame with the RSSI signal strength (TX2), then switches into OFF mode.
  4. If the base station does not receive any acknowledgment packet from the remote sensor within 400 ms timeout, the base station displays the error message, as shown below, on ATOLED1-XPRO OLED and changes its mode from RX mode to Polling mode to poll for the temperature telegram.
    RF telegram error: NoRF ACK telegram!
  5. The base station reads the acknowledgment frame with the RSSI data (RX2), displays the result, then switches back into the Polling mode.
Figure 3-1. Signal Timing