Neo_M660A GPRS Module Hardware User Guide
Copyright © Neoway Technology Co., Ltd
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Parallel a 1 μF filter capacitor on VBUS and place it as close to the pin as possible. You must also add
TVS to the VBUS power cable. Use TVS diodes with a capacity of lower than 12 pF for protection on the
data cables of USB_DP and USB_DM and adopt Differential Signal trace for USB_DP and USB_DM and
ensure complete ground for separation.
USB interface is used only for software download.
3.4
DTR and RING
Table 3-4
DTR and RING pins
Pin Name
I/O
Function
Remarks
DTR
DI
Signal for controlling sleep mode
Low level by default
Left disconnected if not used
RING
DO
Ring output
Left disconnected if not used
3.4.1 DTR Pin
Generally DTR is used to control sleep mode together with AT commands. For details, see
Neo_M660A
GPRS Module AT Command Set
. Based on the setting of the selected mode, pulling DTR low will bring the
module into sleep mode if the module is idle. In this mode, the idle current is less than 2 mA, depending on
the DRX setting of network.
In sleep mode, the module can respond to the incoming call, SMS, and GPRS data. The host MCU can also
control the module to exit sleep mode by controlling DTR.
Process of entering the sleep mode:
1.
Keep DTR high level in normal working mode. Activate the sleep mode by using the
AT+ENPWRSAVE=1
command.
2.
Pull DTR low, and the module will enter sleep mode, but only after process and pending data
finished.
3.
In the sleep mode, the external MCP can pull DTR high so that the module will exit from sleep mode
actively. Then the module can transmit data and initiate calls. After processing is finished, pull DTR
low again to take the module back to sleep mode.
4.
In sleep mode, the module can be woken up by the events of incoming voice call, received data, or
SMS. Meanwhile the module will send out the unsolicited messages through the UART.
Upon receipt of the unsolicited messages, the host MCU should pull DTR high firstly, otherwise the
module will resume sleep mode in two minutes after the service processing. And then the host MCU
can process the voice call, received data, or SMS. After processing is finished, pull DTR low again to
put the module into sleep mode.
3.4.2 RING Signal Indicator
Calling: Once a voice call is coming, UART output "RING" character strings and meanwhile the
RING pin outputs 250 ms low pulses at 4s period. After the call is answered, the high level restores.