EVM-900-DT Ver la hoja de datos (PDF) - Unspecified

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EVM-900-DT

HumDT™ Series RF Transceiver Module

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The Command Data Interface Command Set

The following sections describe the commands and parameters.

Note: All values are shown in hexadecimal format unless otherwise

stated.

The module has two forms of memory, volatile and non-volatile. Volatile

memory is temporary and all values are lost when power is removed from

the module. However, it is faster to access and the module typically uses

the values in volatile memory during operation.

Non-volatile memory is retained when power is removed from the module.

This is where default values are stored. When the module powers on, it

pulls some values from non-volatile memory and loads them into volatile

memory for use during normal operation.

There is one command to read (Command Code = 22) and one command

to write (Command Code = 23) all of the configurations in non-volatile

memory. The non-volatile memory has a life expectancy of about 1,000

writes, so using one command for all settings helps extend the life time.

Volatile settings have separate commands for each setting since it has

a much larger life expectancy. This makes it easier to change just one

configuration value.

Send Data Packet - Command Code = 21

This command instructs the module to transmit a data packet over the air.

Send Data Packet Command and Response

Command

Start Cmd Param 1 Param 2 Param 3 Param 4 Param 5 Data End

3C 21 DestAdr3 DestAdr2 DestAdr1 DestAdr0 LEN DATA 3E

Response

Start Rsp Param1

End

3C 21 Status

3E

Figure 21: Send Data Packet Command and Response

The first four bytes consist of the destination address for the data packet

with the DestAdr3 (Param 1 byte) being the Most Significant Byte (MSB).

The Len byte (Param 5) is the total number of bytes in the Parameter and

Data fields (5 bytes plus the number of data bytes).

– 24 –

The Data field contains 0 to 32 bytes of user defined data.

The response parameter indicates if the module successfully processed

the command (0x00) or if there was an error (0x01). It only indicates that

the data packet has been successfully transmitted by module. It does not

indicate that the data was successfully received by the remote device.

When data is received by the module, the output format follows the

same format with two exceptions. The source address (address of the

transmitting module) replaces the destination address and the module adds

one or two RSSI bytes to the end of the response.

The RSSI values depend on the number of hops the packet took. From AP

to ED is one hop and only one RSSI byte is added. Transmissions from one

ED to another ED must go through the AP, so there are two hops. RSSI1 is

the first hop, RSSI2 is the second hop. There is no placeholder, so RSSI2 is

either there or not.

The LEN byte includes the Parameter, Data and RSSI bytes.

Received Data Packet Output

Start Cmd Param 1 Param 2 Param 3 Param 4 Param 5 Data RSSI1 RSSI2 End

3C 20 SrcAdr3 SrcAdr2 SrcAdr1 SrcAdr0 LEN DATA RSSI1 RSSI2 3E

Figure 22: Received Data Packet CDI Output

The RSSI value is returned in 2’s complement hex format. The RSSI value

in dBm can be calculated based on the formula shown below.

RSSI (dBm) = RSSI_value (in the response) - 256

– 25 –

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