Transceivermodule 1 TRX433-10A / TRX868-10A (Vers. 1.0E ...

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Transceivermodule 6 TRX433-10A / TRX868-10A (Vers. 1.0E) Linkcontrol mode Pin 9 (TEST) of the Transceivermodule has two functions, one for the flow-control (handshake) and the second function is the link-control. The link-control signals a valid, bidirectional link to a second partner- Transceivermodule. If TEST is set high through a resistor, the status of the radio-link to the partnermodem is output on the signal LINK\. LINK\ low means radio communication is OK LINK\ high means no radio communication Because TEST as well as LINK\ are double used and depending on the application are used as an input or an output, please take care not to connect two outputs without any current-limitation resistor together and also prevent the situation of an open input. As an example we refer to the application schematic of the Evalkit3, where the link-control is realized with a push-button and a LED. Important notice: Pin 9 must be connected with a Pulldown resistor (e.g. 100 k) to GND, so that the configuration mode cannot be activated unintentional during powerup of the Transceivermodule. If during powerup pin 9 is already high, the configuration mode is activated. RSSI (Received Signal Strenght indicator) The voltage at pin 8 (RSSI) is directly proportional to the receiving field intensity. The higher this voltage is the higher is also the receiving field intensity. The scaling is approx. 29dB/V, the offset or zero point is not calibrated and depends on the RF-mode. Powersupply The Radiotransceiver needs a clean supply voltage of min. 3.5V with a ripple of < 10mVpp. The power amplifier of the radio transmitter is directly connected to the input supply voltage, the rf-transmitter power therefore depends a little on the input supply voltage. If the supply of the Transceivermodule is switched, the voltage must always sink to 0V, before switching on the supply again. The supply voltage must rise within max. 50ms from 0V to 3.5V, so that the integrated microcontroller starts correctly. The voltage may never fall below 3.3 V, not even for a short time. If this cannot be ensured, the supply voltage must be supervised by a Voltagedetector, which ties the MCLR\ input low as soon as the voltage drops below approx. 3.3V. See also application example with Evalkit3. Datainterface with 5V Systems The logic levels of the Transceivermodule are 3.3 Volt, according to the int. voltage regulator. The Transceiver can work directly at 5Volt systems, however during the high level of the 5V system an additional small current flows over the internal series resistors into the Transceiver. The input high-levels of the 5V system must be compatible to the 3.3V logic. See also simplified schematic of the Transceiver MCLR\ Reset The microcontroller of the Transceivermodule hasn’t got an internal Reset-detector, so the reset pin is externally accessible. We recommend an external Voltage detector with a trip voltage of > 3.3Volt (for standard TRX with 3.3V internal voltage regulator). If no such detector is used, please read the datasheet of the Microchip 16LF648A and ensure that the supply voltage conditions for powerup, brownout etc. can be met. The most problematic situation exists, when the supply voltage drops below 3.5 Volt and then again rises to normal condition, without going to nearly zero Volt. Anyway, with an external voltage detector, these problems are solved. If the conditions described under paragraph Powersupply are all met, the external reset-controller or voltage detector can be omitted.
Transceivermodule 7 TRX433-10A / TRX868-10A (Vers. 1.0E) Timing and Handshake of communication The following example shows an unidirectional data communication of DEVICE1 to DEVICE2 with hardware handshake. If the data source sends more data than the Transceiver can buffer (>31 byte), a handshake is absolutely necessary, so that no data are lost. The databuffer of DEVICE1 is sent, as soon as it is full or if during the time of 3ms no more data arrive. The data communication is symmetrical and identical in both directions. The Transceiver data are double buffered (2x31 bytes) at the transmitter side. The first Buffer takes up the data from RS232 and passes them to the transmitter buffer before the start of the transmission. There the data are kept until an answer (ACK) from the receiver confirms the successful radio transmission. Meanwhile the first Buffer receives already new data from the RS232. The transmitter repeats the radio transmission of the data in the transmitter buffer as long as he receives a successful answer (ACK) from DEVICE2. Then, the next data block from the RS232 Buffer will be shifted into the transmitter buffer. The data buffer at the receiver-side is designed as a ringbuffer. This allows to receive new data over radio as soon as the buffer is going to be emptied into the RS232 interface. RXD_1 RTS_1 Radio1 state TXD_1 CTS_1 TXD_2 CTS_2 Radio 2 state RXD_2 RTS_2 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 Transceiver DEVICE 1 sends 70 Bytes receive 31 Databytes Transceiver DEVICE 2 receive 31 Databytes Tdata Tradio transmit Tdelay Schematic with Hardwarehandshake PC, Terminal RTS TXD RXD CTS TRX, DEVICE 1 CTS RXD TXD RTS RX Buffer1 full receive 31 Bytes 70 Bytes from DEVICE 1 31 Bytes 8 Bytes ACK acknowledge RADIO Link 8 Databytes transmit receive TRX, DEVICE 2 CTS RXD TXD RTS receive ACK acknowledge transmit receive ACK acknowledge PC, Terminal RTS TXD RXD CTS
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