Overview
This guide explains how to configure and operate ultra-low power mode on Siretta NLP series modems. It covers low power functionality, DTR sleep control, socket communication in low power mode, RTS/CTS flow control and optimisation techniques for battery-powered IoT systems.
| Part Number | Description |
|---|---|
| ZETA-NLP-LTE1 (EU) | Ultra Low Power European LTE Cat 1 Modem |
| ZETA-NLP-LTEM (GL) | Ultra Low Power Global LTE Cat M Modem |
This guide demonstrates how to:
Expected Result
At the end of this guide the modem should be capable of operating in ultra-low power mode whilst remaining registered on the cellular network.
The ZETA-NLP modem family supports a special ultra-low power operational mode.
In this mode:
This allows the modem to:
Important Note
In ultra-low power mode the modem may appear OFF because the serial interface becomes inactive.
Ultra-low power functionality is enabled using the AT+CFUN=5 command.
| COM3 - Tera Term VT |
¶ File Edit Setup Control Window Help |
|
AT+CFUN=5 |
| Command | Description |
|---|---|
AT+CFUN=5 |
Enables ultra-low power functionality |
Expected Result
The modem should enter reduced functionality mode and prepare for ultra-low power operation.
Ultra-low power state entry is controlled using the RS232 DTR (Data Terminal Ready) signal.
Once AT+CFUN=5 has been enabled:
Important Note
The modem will not respond to AT commands while DTR is de-asserted and the modem is dormant.
The following RS232 signals are used for low power control.
| Pin | Signal | Description | Direction |
|---|---|---|---|
| 1 | DCD | Carrier detect | OUT |
| 2 | RXD | UART transmit line | OUT |
| 3 | TXD | UART receive line | IN |
| 4 | DTR | Controls low power state | IN |
| 5 | GND | Ground | - |
| 6 | DSR | Modem ready indication | OUT |
| 7 | RTS | Hardware flow control | IN |
| 8 | CTS | Hardware flow control | OUT |
| 9 | RI | Ring indication | OUT |
To control DTR and RTS correctly, terminal software must support hardware control signalling.
Recommended applications:
Important Note
Standard terminal applications without DTR/RTS control may not support ultra-low power operation correctly.
The modem can maintain an active socket connection while operating in ultra-low power state.
| COM3 - Tera Term VT |
¶ File Edit Setup Control Window Help |
|
AT&K3 |
| Command | Description |
|---|---|
AT&K3 |
Enables RTS/CTS hardware flow control |
Before opening a socket connection the packet data context must be configured.
| COM3 - Tera Term VT |
¶ File Edit Setup Control Window Help |
|
AT+CGDCONT=1,"IP","APN_NAME" |
| COM3 - Packet Data Context |
¶ File Edit Setup Control Window Help |
|
AT#SGACT=1,1,"username","password" #SGACT: 10.161.45.82 OK |
Expected Result
The modem should activate the packet data session and return a valid IP address.
| COM3 - Socket Configuration |
¶ File Edit Setup Control Window Help |
|
AT#SCFG=1,1,300,90,600,50 |
| COM3 - Socket Connection |
¶ File Edit Setup Control Window Help |
|
AT#SD=1,0,41032,"device.siretta-link.com",255,0 CONNECT |
| COM3 - Connected Socket Session |
¶ File Edit Setup Control Window Help |
|
-------------------------------------------------- |
Once the socket is active:
When the polling interval expires:
| Step | Action |
|---|---|
| 1 | Assert DTR |
| 2 | Assert RTS |
| 3 | Receive buffered socket data |
| 4 | De-assert RTS |
| 5 | De-assert DTR |
While waiting for incoming data:
Important Note
Pending cellular network data increases power consumption until buffered data is read from the modem.
| COM3 - Incoming Socket Data |
¶ File Edit Setup Control Window Help |
|
456 - 01234567890 ----- abcdefghijklmnopqrstuvwxyz ----- ABCDEFGHIJKLMNOPQRSTUVWXYZ ----- PING |
| COM3 - Exit Online Mode |
¶ File Edit Setup Control Window Help |
|
+++ |
| COM3 - Disconnect Packet Context |
¶ File Edit Setup Control Window Help |
|
AT#SGACT=1,0 |
| Recommendation | Benefit |
|---|---|
| Use long polling intervals | Reduces average current |
| Disable unused interfaces | Reduces idle power |
| Buffer incoming data | Reduces wake frequency |
| Use RTS/CTS correctly | Prevents serial overflow |
| Optimise socket activity | Minimises RF usage |
| Problem | Possible Cause | Solution |
|---|---|---|
| Modem appears OFF | DTR de-asserted | Assert DTR |
| No serial response | Dormant state active | Wake modem |
| Socket data missing | RTS inactive | Assert RTS |
| Increased current draw | Pending network data | Read buffered data |
| Modem never sleeps | DTR permanently asserted | Control DTR correctly |
| Step | Action |
|---|---|
| 1 | Configure APN |
| 2 | Activate packet context |
| 3 | Enable hardware flow control |
| 4 | Enable ultra-low power mode |
| 5 | Open socket connection |
| 6 | De-assert DTR and RTS |
| 7 | Poll for incoming data |
| 8 | Re-enter low power state |
Support
For further assistance, please contact the Siretta support team.