SI4438 Wireless Module
User Manual of E30 Series Modules
Copyright ©2012–2017, Chengdu Ebyte Electronic Technology Co., Ltd.
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6.1 Mode Switch
The user can decide the operating mode by the combination of M1 and M0. The two GPIOs of MCU can be used to switch mode.
After modifying M1 or M0, it will start to work in new mode 1ms later if the module is free. If there are any serial data that are yet to
finish wireless transmitting, it will start to work in new mode after the UART transmitting finished. After the module receives the
wireless data & transmits the data through serial port, it will start to work in new mode after the transmitting finished. Therefore,
the mode-switch is only valid when AUX outputs 1, otherwise it will delay.
For example, in mode 0 or mode 1, if the user inputs massive data consecutively and switches operating mode at the same time, the
mode-switch operation is invalid. New mode checking can only be started after all the user ’ s data process completed. It is
recommended to check AUX pin out status and wait 2ms after AUX outputs high level before switching the mode.
If the module switches from other modes to stand-by mode, it will work in stand-by mode only after all the remained data process
completed. The feature can be used to save power consumption. For example, when the transmitter works in mode 0, after the
external MCU transmits data “12345”, it can switch to sleep mode immediately without waiting the rising edge of the AUX pin, also
the user’s main MCU will go dormancy immediately. Then the module will transmit all the data through wireless transmission & go
dormancy 1ms later automatically, which reduces MCU working time & save power.
Likewise, this feature can be used in any mode-switch. The module will start to work in new mode within 1ms after completing
present mode task, which enables the user to omit the procedure of AUX inquiry and switch mode swiftly. For example, when
switching from transmitting mode to receiving mode, the user MCU can go dormancy before mode-switch, using external interrupt
function to get AUX change so that the mode-switch can be realized.
This operation is very flexible and efficient. It is totally designed on the basis of the user MCU’s convenience, at the same time the
work load and power consumption of the whole system has been reduced and the efficiency of whole system is largely improved.
6.2 Normal Mode (Mode 0)
When M1 = 0 & M0 = 0, module works in mode 0
Transmitting
The module can receive the user data via serial port, and transmit wireless data package of 58 bytes. When the data
inputted by user is up to 58 byte, the module will start wireless transmission. During which the user can input data
continuously for transmission.
When the required transmission bytes are less than 58 bytes, the module will wait 3-byte time and treat it as data
termination unless continuous data inputted by user. Then the module will transmit all the data through wireless
channel.
When the module receives the first data packet from user, the AUX outputs low level.
After all the data are transmitted into RF chip and transmission start , AUX outputs high level.
At this time, it means that the last wireless data package transmission is started, which enables the user to input another
512 bytes continuously. The data package transmitted from the module working in mode 0 can only be received by the
module working in mode 0 or 1.
Receiving
The wireless receiving function of the module is on, the data packet transmitted from the module working in mode 0 &
mode 1 can be received.
After the data packet is received, the AUX outputs low level, 5ms later the module starts to transmit wireless data
through serial port TXD pin.
After all the wireless data have been transmitted via serial port, the AUX outputs high level.
6.3 Wake-up Mode (Mode 1)
When M1 = 0 & M0 = 1, module works in mode 1
Transmitting
The condition of data packet transmission & AUX function is the same as mode 0. The only difference is that the
module will add preamble code before each data packet automatically. The preamble code length depends on the
wake-up time set in the user parameters. The purpose of the preamble code is waking up the receiving module works in
mode 2. Therefore, the data package transmitted from mode 1 can be received by mode 0, mode1 and mode 2.
Receiving
The same as that in mode 0.
