WI.232FHSS-25-R datasheet(28/67 Pages) RADIOMETRIX

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WI.232FHSS-25-R/ WI.232FHSS-250-R DATASHEET

Revision 1.1.0

3.4. Power Supply

Although the Wi.232FHSS module is very easy to use, care must be given to the design of the power

supply circuit. It is important for the power supply to be free of digital noise generated by other parts of the

application circuit, such as the RS-232 converter.

Figure 11 shows the schematic for our evaluation module circuit for the Wi.232FHSS-25-R and

Wi.232FHSS-250-R modules. The EVM includes an on-board power supply and antenna connector.

These evaluation circuits were used to measure the performance of the Wi.232FHSS module, and should

be used as a reference for Wi.232FHSS based designs.

If noise is a problem, it can usually be eliminated by using a dedicated LDO regulator for the module and/or

by separating the grounds for the module and the other circuits.

Additionally, power supply rise time is extremely important. The power supply presented to the module

must rise from Vss to 2.7V in less than 1ms. If this specification cannot be met, an external reset

supervisor circuit must be used to hold the module in reset until the power supply stabilizes. Failure to

ensure adequate power supply rise time can result in loss of important module configuration

information.

The Wi.232FHSS-250-R module power supply should be bypassed as close to the module as possible for

maximum noise immunity (C1 and C2 in figure 11). Also, an inductor or ferrite choke may be placed close

to the module, in series with the supply line to further reduce any noise being conducted back onto the

supply from the module. Noise on the power supply can degrade receiver performance and cause other

instabilities.

3.5. UART Interface

The UART interface is very simple; it is comprised of four CMOS compatible digital lines.

Direction

Description

CTS

Out

Clear to send – this pin indicates to the host micro when it is ok to send data.

When CTS is high, the host micro should stop sending data to the module

until CTS returns to the low state.

CMD

Command – the host micro will bring this pin low to put the module in

command mode. Command mode is used to set and read the internal

registers that control the operation of the module. When CMD is high, the

module will transparently transfer data to and from other modules on the

same channel.

Note: If this pin is low when the module comes out of reset, the non-volatile

registers will be reset to their factory programmed defaults. It is important to

ensure that CMD is held high or left floating during power-up under normal

conditions.

RxD

Receive data input. UART data should be sent to the module with no parity, 1

start bit, 1 stop bit, 8 data bits, least-significant bit first.

TxD

Out

Transmit data output. UART data will be sent by the module with no parity, 1

start bit, 1 stop bit, 8 data bits, least-significant bit first.

RTS

Currently unimplemented, this pin is reserved for future use/reassignment.

Table 9, Wi.232FHSS-25–R and WI.232FHSS-250-R UART Interface Lines

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