U-blox Sara-u201 Sara Migration User Guide

u-blox SARA-U201 SARA Migration

Abstract
This document provides hardware design guidelines to migrate between u-blox cellular modules based on SARA form factor. u-blox cellular modules having 2G, 3G, LTE-M, NB-IoT as dominant technology use this compact form factor to provide complete and cost-efficient solutions, specifically designed for IoT, offering multi-band data transmission.

Document information

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SARA-R4/SARA-R5 modules description

u-blox SARA-R4 series LTE-M / NB-IoT / EGPRS and SARA-R5 series LTE-M / NB-IoT modules are ideal for IoT solutions, in the miniature SARA LGA form factor (26.0 x 16.0 mm, 96-pin).
They are easily integrated into compact designs and provide a seamless drop-in migration from other u-blox LPWA, GSM/GPRS, CDMA, UMTS/HSPA and LTE module families. They are form-factor compatible with the u-blox LISA, LARA and TOBY cellular module families and they are pin-to-pin compatible with the u-blox SARA-N, SARA-G and SARA-U cellular module families, thus maximizing customer investments, simplifying application design, and enabling a very short time-to-market.
Table 1 summarizes the main features and interfaces of SARA-R4 and SARA-R5 series modules.
With a discrete, hardware-based secure element and a lightweight pre-shared key management system, SARA-R5 series modules offer state-of-the-art security that is ideal for IoT applications and includes data encryption and decryption, zero touch provisioning, anti-cloning, and secure chip-to-chip communication. SARA-R4 and SARA-R5 series modules are the optimal choice for LPWA applications with low to medium data throughput rates, as well as devices that require long battery lifetimes, such as used in smart metering, smart cities, telematics, and connected health.
The modules support handover capability and deliver the technology necessary for use in applications such as vehicle, asset and people tracking where mobility is a pre-requisite. Other applications where the modules are well-suited include but are not limited to: smart home, security systems, industrial monitoring and control.
The modules support multi-band data communication over an extended operating temperature range of –40 to +85 °C, with extremely low power consumption, and with coverage enhancement for deeper range into buildings and basements (and underground with NB-IoT).
Table 2 summarizes cellular and GNSS characteristics of SARA-R4/R5 modules.

1. Not supported by SARA-R410M-52B-01 or SARA-R410M-52B-02 product version
2. Not supported by SARA-R410M-63B or SARA-R410M-73B product versions
3. LTE Cat NB2 not supported by SARA-R500S-00B, SARA-R510S-00B, SARA-R510M8S-00B product versions
4. Not supported in LTE Cat NB1 by SARA-R410M-02B-01, SARA-R410M-02B-02, or SARA-R410M-02B-03 product version
5. Not supported by SARA-R410M-83B product version
6. LTE Cat NB1 not supported by SARA-R410M-52B, SARA-R410M-63B, SARA-R410M-73B product versions
   

   Feature	SARA-R410M	SARA-R412M	SARA-R422 SARA-R422S SARA-R422M8S	SARA-R500S SARA-R510S SARA-R510M8S
   Data rate	LTE Cat M1: up to 375 kbit/s UL up to 300 kbit/s DL	LTE Cat M1: up to 375 kbit/s UL up to 300 kbit/s DL	LTE Cat M1: up to 1119 kbit/s UL up to 588 kbit/s DL	LTE Cat M1: up to 1200 kbit/s UL up to 375 kbit/s DL
   	LTE Cat NB17: up to 62.5 kbit/s UL up to 27.2 kbit/s DL	LTE Cat NB1: up to 62.5 kbit/s UL up to 27.2 kbit/s DL	LTE Cat NB2: up to 158.5 kbit/s UL up to 127 kbit/s DL	LTE Cat NB29: up to 140 kbit/s UL up to 125 kbit/s DL
   		GPRS multi-slot class 338 up to 85.6 kbit/s UL up to 107 Kbit/s DL	GPRS multi-slot class 338 up to 85.6 kbit/s UL up to 107 kbit/s DL
   		EGPRS multi-slot class 338 up to 236.8 kbit/s UL up to 296.0 kbit/s DL	EGPRS multi-slot class 338 up to 236.8 kbit/s UL up to 296.0 kbit/s DL
   GNSS receiver			SARA-R422M8S only:	SARA-R510M8S only:
   			72-channel u-blox M8 engine	72-channel u-blox M8 engine
   			GPS L1C/A SBAS L1C/A QZSS L1C/A QZSS L1-SAIF GLONASS L10F BeiDou B1I Galileo E1B/C	GPS L1C/A SBAS L1C/A QZSS L1C/A QZSS L1-SAIF GLONASS L10F BeiDou B1I Galileo E1B/C

7. LTE Cat NB1 not supported by SARA-R410M-52B, SARA-R410M-63B, SARA-R410M-73B product versions
8. GPRS/EGPRS multi-slot class 33 implies a maximum of 5 slots in downlink and 4 slots in uplink, with 6 slots in total
9. LTE Cat NB2 not supported by SARA-R500S-00B, SARA-R510S-00B, SARA-R510M8S-00B product versions

SARA-N2/SARA-N3 modules description

SARA-N2 and SARA-N3 series modules are NB-IoT solutions in the miniature SARA LGA form factor (26.0 x 16.0 mm, 96-pin), offering LTE Cat NB1 / NB2 data communication over an extended operating temperature range of –40 to +85 °C, with extremely low power consumption.
The SARA-N2 series includes four variants supporting single-band NB-IoT data communication for Europe, China, APAC and South America, plus a dual-band variant mainly designed for Europe.
The SARA-N3 series offers multi-band NB-IoT data communication enabling multi-regional coverage, and they introduce several new functionalities for NB-IoT products, including features like TCP, MQTT, DTLS, SSL/TLS, LwM2M, HTTP(S) and many others.
SARA-N2 and SARA-N3 modules are ideally suited to battery-powered IoT applications characterized by occasional communications of small amounts of data.
The modules are the optimal choice for IoT devices designed to operate in locations with very limited coverage and requiring low energy consumption to permit a very long operating life with the primary batteries. Examples of applications include and are not limited to: smart grids, smart metering, telematics, street lighting, environmental monitoring and control, security and asset tracking.
Table 3 describes a summary of interfaces and features provided by SARA-N2 and SARA-N3 modules.
Table 4 summarizes cellular radio access technology characteristics of SARA-N2 / SARA-N3 modules.

• 10 Additional bands (1, 2, 4, 12, 13, 18, 19, 26, 66, 71, 85) available in future FW versions
• 11 Key subset of features
• 12 Configurable to other power class by AT command

Migration between SARA modules

Overview

The u-blox SARA form factor (26.0 x 16.0 mm, 96-pin LGA) includes the following series of modules, with compatible pin assignments as described in Figure 1, so that the modules can be alternatively mounted on a single application PCB using exactly the same copper, solder resist and paste mask:

• SARA-R41 series modules supporting LTE Cat M1, LTE Cat NB1 and 2G radio access technologies
• SARA-R42 series modules supporting LTE Cat M1, LTE Cat NB2 and 2G radio access technologies
• SARA-R5 series modules supporting LTE Cat M1 and LTE Cat NB2 radio access technologies
• SARA-N2 series modules supporting LTE Cat NB1 radio access technology
• SARA-N3 series modules supporting LTE Cat NB2 radio access technology
• SARA-G3 series modules supporting 2G radio access technology
• SARA-G4 series modules supporting 2G radio access technology
• SARA-U2 series modules supporting 3G and 2G radio access technologies

The SARA modules are also form-factor compatible with the u-blox LARA, LISA, and TOBY cellular module families. Although each has a different form factor, the footprints for the TOBY, LISA, LARA, and SARA modules have been developed to ensure layout compatibility.
With the u-blox “nested design” solution, any TOBY, LISA, LARA, or SARA module can be alternatively mounted on the same space of a single “nested” application board as described in Figure 2. Guidelines to implement a nested application board, description of the u-blox reference nested design and comparison between TOBY, LISA, LARA and SARA modules are provided in the nested design application note [10].
Figure 2: Cellular modules’ layout compatibility: all modules can be mounted on the same nested footprint
Table 5 summarizes the main interfaces provided by SARA modules:
Figure 3 summarizes the frequency ranges of the SARA modules’ operating bands.

Pin-out comparison between SARA modules

Table 6 shows a pin-out comparison between the SARA-R4, SARA-R5, SARA-N2, SARA-N3, SARA-G3, SARA-G4, and SARA-U2 modules.

Schematic for SARA modules integration

Figure 4 shows an example of a simple schematic diagram where a u-blox SARA-N2, SARA-N3, SARA-R4, SARA-R5, SARA-G3, SARA-G4, and/or SARA-U2 module is integrated in the same application board, using the main available interfaces and functions of the modules.
The different mounting options for the external parts are highlighted in different colors as described in the legend, according to the interfaces supported by each module, and related characteristics.
VCC supply
In the simple schematic diagram shown in Figure 4, the VCC supply of the SARA modules is provided by a suitable supply source, at 3.6 V nominal voltage, not illustrated in the diagram. The application processor controls the VCC supply of the modules by means of a high-side switch. Proper bypass capacitors and EMI filter parts are placed close to the VCC input pins of the modules.
While selecting the supply source for SARA cellular modules, consider with adequate safe design margin the maximum current consumption of each SARA cellular module (see related data sheet [1], [5], [6], [7], [11], [12], [13]), as it reflects the RATs supported. For additional specific design guidelines, see the VCC interface sections in the related system integration manual [2], [8], [9], [14], [15].
The switch-on sequence of SARA-N2, SARA-R500S, SARA-R510M8S, SARA-G3 and SARA-U2 starts by applying a valid VCC supply.
Instead, SARA-N3, SARA-R4, SARA-R510S and SARA-G4 modules continue to be switched off even after a valid VCC supply has been applied: the PWR_ON input line has to be properly toggled, with valid VCC supply present, to start the switch-on sequence of these modules.
UART serial interface
The application processor is connected to the SARA modules over main UART interface in the simple schematic diagram illustrated in Figure 4.
The design is implemented with the UART interface configured at the same voltage level on both sides (application processor and SARA module), without using voltage translators, as is recommended in order to minimize any possible leakage and benefit from the extremely low current consumption of the u-blox LPWA modules, in particular in deep sleep Power Saving Mode.
Thus, the supply level of the application processor is selected to properly set its UART voltage level:

• at the VCC level of the module (3.6 V nominal), in case of SARA-N2
• at the V_INT level of the module (2.8 V nominal, with VSEL unconnected), in case of SARA-N3
• at the V_INT level of the module (3.0 V nominal, with VSEL unconnected), in case of SARA-G4
• at the V_INT level of the module (1.8 V nominal), for all the other SARA modules

The TXD and RXD data lines, supported by all the SARA modules for AT and data communication, are directly connected with the application processors. For additional specific design guidelines, see the UART sections in the related system integration manual [2], [8], [9], [14], [15].
The RTS, CTS and RI lines are connected to the application processors by 0 Ω jumpers for all the u-blox SARA modules except the SARA-N2 series, which does not support hardware flow control functionality and instead supports RI functionality over the CTS output pin.
The other UART lines are not implemented in the simple example of design shown in Figure 4, and the DTR input is grounded as required to have URCs and/or the greeting text sent by SARA-R4, SARA-R5 and SARA-U2 modules.
System control interfaces
The application processor controls the PWR_ON / PWR_CTRL line by means of an open drain driver in the circuit illustrated in Figure 4, with an external pull-up to V_BCKP for SARA-G3 and SARA-U2 modules. The whole circuit need not be populated for SARA-N2 modules, which do not provide PWR_ON / PWR_CTRL input.
The application processor controls the RESET_N / PWR_OFF line by means of open drain driver too. The assertion or toggling of this line causes different actions:

• the RESET_N line triggers an unconditional reboot of the module when toggled, without internal PMU shutdown when set low, in case of SARA-N2, SARA-R5 and SARA-G3
• the RESET_N line triggers an unconditional reboot of the module when toggled, with internal PMU shutdown when set low, in case of SARA-N3 and SARA-U2
• the RESET_N / PWR_OFF line triggers an unconditional shutdown of the module when set low or toggled, in case of SARA-R4 and SARA-G4

The circuit need not be populated for SARA-R42x modules, not providing RESET_N / PWR_OFF input.
The timings for proper control of the PWR_ON / PWR_CTRL, RESET_N / PWR_OFF lines of the SARA modules are reported in the related data sheet [1], [5], [6], [7], [11], [12], [13].
Cellular RF interface
Figure 4 shows the ANT cellular antenna circuit implemented with the optional ANT_DET antenna detection circuit according to the design guidelines provided in the antenna interface sections of the related system integration manual [2], [8], [9], [14], [15].
While selecting the antenna for SARA cellular modules, consider the frequency range supported by each SARA module, as illustrated in Figure 3.
Designers must consider the antenna from all perspectives at the very start of the design phase when the physical dimensions of the application board are under analysis/decision, since the RF compliance of the end-device integrating cellular modules with all the applicable required certification schemes depends on the antenna’s radiating performance.
While implementing the cellular RF antenna design for SARA modules, consider providing the best possible return loss in the frequency range supported by the modules, and place the antenna far from VCC supply line and related parts, as well as far from any possible source of interference and/or noise.
GNSS RF interface
Figure 4 shows the ANT_GNSS circuit implemented for the SARA-R422M8S and SARA-R510M8S modules, which integrate the u-blox M8 GNSS receiver chip. The module ANT_GNSS RF input is connected to a GNSS antenna without additional external SAW and LNA, because dedicated band-pass SAW and LNA are already integrated in the modules along the internal GNSS RF path.
Similar to the cellular RF antenna design, the GNSS RF antenna design needs to provide the best possible return loss in the GNSS frequency range supported by the modules, and should have the antenna placed far from any possible source of interference and/or noise.
SIM interface
Figure 4 also shows the SIM interface circuit implemented with the optional SIM detection function, according to the design guidelines provided in SIM interface sections of the related system integration manual [2], [8], [9], [14], [15]. Bypass capacitors with proper self-resonant frequency are recommended to be placed close to the SIM connector, as well as ESD protections.
GPIO interface
Figure 4 also shows the GPIO1 that controls an LED, which provides the network status indication. It is supported by all SARA modules (except SARA-N2 series) that can provide this function on the CTS pin. Other functions can be enabled on the GPIOs of the SARA modules, as described in the related data sheet [1], [5], [6], [7], [11], [12], [13] and related AT commands manual [3], [4], [16], [17].
Test-Points
Table 7 lists the interfaces dedicated for FW update and/or diagnostic purposes on SARA modules.

The schematic diagram illustrated in Figure 4 includes accessible test-points directly connected to the following pins, which are strongly recommended for FW update and/or diagnostic purposes:

• V_INT
• PWR_ON/PWR_CTRL
• RESET_N/PWR_OFF
• TXD
• RXD
• GPIO1
• VUSB_DET/USB_5V0
• USB_3V3
• USB_D+/TXD_FT/TXD_AUX
• USB_D‒/RXD_FT/RXD_AUX
• RSVD #33
• TXD_GNSS
• DCD
• DTR

Other
All the GND pins are intended to be externally connected to ground, while other interfaces are not implemented or not used in the simple example of design as shown in Figure 4.
For additional specific design guidelines, see the related system integration manual [2], [8], [9],[14], [15] of the u-blox SARA modules.

Glossary

Table 8: Explanation of the abbreviations and terms used

Related documentation

1. u-blox SARA-R5 series data sheet, UBX-19016638
2. u-blox SARA-R5 series system integration manual, UBX-19041356
3. u-blox SARA-R5 series AT commands manual, UBX-19047455
4. u-blox SARA-R4 series AT commands manual, UBX-17003787
5. u-blox SARA-G3 series data sheet, UBX-13000993
6. u-blox SARA-U2 series data sheet, UBX-13005287
7. u-blox SARA-N2 series data sheet, UBX-15025564
8. u-blox SARA-G3/SARA-U2 series system integration manual, UBX-13000995
9. u-blox SARA-N2/SARA-N3 series system integration manual, UBX-17005143
10. u-blox nested design application note, UBX-16007243
11. u-blox SARA-R4 series data sheet, UBX-16024152
12. u-blox SARA-N3 series data sheet, UBX-18066692
13. u-blox SARA-G4 series data sheet, UBX-18006165
14. u-blox SARA-R4 series system integration manual, UBX-16029218
15. u-blox SARA-G4 series system integration manual, UBX-18046432
16. u-blox AT commands manual, UBX-13002752
17. u-blox SARA-N2/SARA-N3 series AT commands manual, UBX-16014887

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Revision history

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References

• Roblox
• Home | u-blox
• Home | u-blox
• u-blox.com/docs/UBX-13000993
• u-blox.com/docs/UBX-13000995
• u-blox.com/docs/UBX-13002752
• u-blox.com/docs/UBX-13005287
• u-blox.com/docs/UBX-15025564
• u-blox.com/docs/UBX-16007243
• u-blox.com/docs/UBX-16014887
• u-blox.com/docs/UBX-16024152
• u-blox.com/docs/UBX-16029218
• u-blox.com/docs/UBX-17003787
• u-blox.com/docs/UBX-17005143
• u-blox.com/docs/UBX-18006165
• u-blox.com/docs/UBX-18046432
• u-blox.com/docs/UBX-18066692
• u-blox.com/docs/UBX-19016638
• u-blox.com/docs/UBX-19041356
• u-blox.com/docs/UBX-19047455