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Transceiver module TRX433-10C2 / TRX868-10C2 (Vers. 1.0E) 6 General information Serial Interface (RS232) There is a serial bidirectional full duplex interface available to communicate with the transceiver module. The data are transmitted and the transceiver module is configured over the same interface. You can choose between data mode and configuration mode with the MODE pin. Data mode (MODE Pin = Low) When the transceiver module receives data over the serial interface then those are automatically transmitted to all transceivers with the same configurations (frequency, RF data rate etc). Then those transceivers output them immediately over the serial interface after a few milliseconds. The baud rate for the RS232transmission can be set from 1.2kbaud to 115.2kbaud 6 . Configuration mode (MODE Pin = High) The transceiver module is configured over the serial interface. There is a comprehensive command set available. The last configuration will stay saved in the internal EEPROM if the accordant bit for saving in EEPROM is set. The configuration can occur in any baud rate from 1.2kbaud to 115.2kbaud 6 (the baud rate is detected automatically in the configuration mode). Radio transmission In the data mode, all the data which was received by the transceiver module over the serial interface are transmitted autonomous via radio. The transceiver module completely does the coding and decoding of the radio transmission. However, you can adjust the radio transmission to your own needs with help of a few simple commands. The following configurations can be done: Frequency selection There are 139 frequencies in 433MHz–band respectively 159 frequencies in 868MHz–band available, in each case in the 12.5 kHz–channel spacing. The frequency can be chosen irrespectively of the adjusted RF data rate. Make sure that on systems with several used frequencies, the frequency separation is at least the same as the occupied channels of the adjusted RF data rate (see table 1). This frequency separation has to be raised as high as possible for a better range. RF data rate The RF data rate can be chosen from 1.2kbits/s to 38.4kbits/s 7 according to requirements. The smaller the RF data rate is chosen, the higher is the radio range between the transceiver modules. RF data rates > 19.2kbits/s are possible but they require an accordant dimensioned loop filter respectively a change in assembling. Through this change, the sensitivity of the receiver with low RF data rates is reduced. The basic model TRXnnn-10C2 is assembled with loop filters for max. 19.2kbits/s. Further radio transmission configurations to the chosen RF data rates are made automatically by the transceiver modules. These configurations for the different possible RF data rates can be found in table 1. RF data rates Coding Modulation FM-deviation IF-bandwidth Occupied channels 1.2 kbit/s 2.4 kbit/s 4.8 kbit/s 9.6 kbit/s 19.2 kbit/s 38.4 kbit/s 7 Manchester GFSK Manchester GFSK NRZ GFSK NRZ GFSK NRZ GFSK NRZ GFSK NRZ GFSK NRZ GFSK +- 2.025 kHz +- 2.025 kHz +- 2.025 kHz +- 2.025 kHz +- 4.050 kHz +- 4.950 kHz +- 9.900 kHz +- 19.80 kHz 9.6 kHz 12.3 kHz 9.6 kHz 12.3 kHz 19.2 kHz 25.6 kHz 51.2 kHz 102.4 kHz 1 x 12.5kHz 1 x 12.5kHz 1 x 12.5kHz 1 x 12.5kHz 2 x 12.5kHz 4 x 12.5kHz 8 x 12.5kHz 12 x 12.5kHz Table 1 RF data rate with corresponding further configurations can be chosen. Comment 433 MHz 868 MHz 433 MHz 868 MHz 6 115.2kbaud requires a 16MHz µP clock frequency 7 RF data rate > 19.2kbits/s requires a modification of the loop filter, therefore a change in assembling and a 16MHz µP clock frequency
Transceiver module TRX433-10C2 / TRX868-10C2 (Vers. 1.0E) 7 Radio telegram structure For the radio transmission, the actual payloads are embedded in a radio telegram. The transceiver module builds the radio telegram and the associated coding and decoding and disburdens the user with that. A complete radio telegram is built according to figure 1. 2ms Startup + Preamble Syncword 2ms + 32 bits 24 bits 8 bits (opt.) Figure 1 structure of the radio telegram Functions of the individual blocks in the radio telegram LengthField DataField CRC16 n x 8/9 bits (depends on fastsend-setting) 16 bits (opt.) 2ms startup: settling time for the transmitter for the reduction of the transient emissions Preamble: allows the receiver to level out to the carrier signal of the transmitter Syncword: indiales start of the data transmission and conduces therefore to the receiver to synchronize LenthField: declares number of bytes payload in the DataField (optional) DataField: effective payload CDC16: checksum for payload in the data field (optional) Postamble: sends for the correct receiving of the last Data bits of the radio telegram Every radio telegram has to consist of 2ms Startup + Preamble, Syncword, DataField and Postamble. The blocks LengthField and CRC16 are, depending on the chosen configuration, added to the radio telegram as well. The duration of the individual blocks depends on the adjusted RF data rate and is calculated out of the number of bits multiplied by the bit duration of the adjusted RF data rate. Only the period of the 2ms Startup stays constantly 2ms with every RF data rate. Transmittion- and receiving buffer The transceiver module has a transmittion - and receiving buffer, 61 bytes each, for the serial interface. Transmittion buffer (TX-BUF) Over RS232 received data are buffered in the transmittion buffer. The space in the transmittion buffer frees byte-by-byte as soon as a byte is inserted into its place in the DataField of the radio telegramm. Receiving buffer (RX-BUF) In the receiving buffer, the over radio received data are buffered until their output over RS232. When the function “Output of the telegram-RSSI” respectively “Output of the no signal condition-RSSI” is enabled then these RSSI-values are buffered in the receiving buffer in addition to the payloads of the radio telegram. Depending on the configuration, there are maximum two additional bytes needed in the receiving buffer per radio telegram. The space in the receiving buffer for the receiving of the radio telegram has to be free by the time the radio telegram receives the actual payloads from the DataField. The space in the receiving buffer is freed byte-by-byte as soon as a byte is output over RS232. Postamble 2 bits
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