Aaeon’s compact “SRG-3352C” IoT gateway is equipped with a TI AM3352, 3x USB, 2x RS-485, 2x GbE, WiFi/BT, mini-PCIe with micro-SIM, and an NB-IoT connector.

It’s always a bit troubling when vendors omit the name of an embedded system’s processor. However, Aaeon’s fanless SRG-3352C Compact Edge IoT Gateway System, which is said to be based on an 800MHz, Cortex-A8 SoC, gives away the mystery in its name: the IoT gateway no doubt features the aging TI Sitara AM3352. No OS support was listed but given the AM3352 — the lowest end model in the AM335x line, with no 3D GPU or PRU-ICSS cores — Linux is almost certainly supported.

SRG-3352C (left) and mounting options
(click images to enlarge)

No price was listed for the SRG-3352C, which is a re-spin of the $265 SRG-3352. The new model adds a WiFi/Bluetooth model and is more power efficient with 1.8W consumption, therefore enabling solar or battery power, says Aaeon.

The SRG-3352C case has been redesigned to replace the front-mounted RS-485 terminal plugs with rear-mounted DB9 connectors. The system is smaller at 110 x 109 x 39mm, edging into mini-PC territory, and is lighter at 430 grams. It also switches the terminal connector for 9-30V power with a DC jack for 10-30V.

Otherwise, the features appear to be same. Once again, the most notable feature is the dedicated connector for long-range NB-IoT wireless communications. (See farther below for more on NB-IoT vs. LoRaWAN.)

SRG-3352C front and back detail views (left) and bottom detail view
(click images to enlarge)

The SRG-3352C is equipped with 1GB DDR3L, 8GB eMMC, and a microSD slot. Major features include 2x GbE, 2x USB 2.0, and 2x RS-485 ports.

Somewhat confusingly, the announcement mentions 2x COM ports but also notes an “RS-232/422/485 expansion slot for Digital I/O, Isolation RS-485, CANBus, Zigbee and IO-Link wireless support.” Although the datasheet does not mention such a slot, the detail view shows an external RS-485 termination resistor switch.

The SRG-3352C provides a mini-PCIe slot in addition to the WiFi/Bluetooth module. Together with the micro-SIM slot and antenna mount, the slot supports 3G/4G LTE modules. Several 4G modules with external antennas are optional. The NB-IoT connector is separate.

Other features on the gateway include 4x GPIO-controlled LEDs, an RTC with 3V CR2032 Lithium battery, an optional external power adapter, and optional DIN-rail and wall-mount kits, The gateway can operate at 0 to 60°C with 10% ~ 95% non-condensing relative humidity tolerance.

 
NB-IoT overview

Narrowband Internet of Things (NB-IoT) , which we have seen on IoT gateways such as Cloud of Things’ DeviceTone IoT Gateway and Raspberry Pi HATs such as Avnet’s Monarch Go Pi HAT, is a Low Power Wide Area Network (LPWAN) technology. NB-IoT shares many traits with LoRaWAN. According to Statista, LoRaWAN and NB-IoT are together likely to represent 85.5 percent of all LPWAN connections by 2023, gradually eclipsing older technologies like SigFox.

Whereas LoRa uses an open protocol, NB-IoT has a licensed protocol from 3GPP and is only available through established mobile network operators. The NB-IoT is closely related to other LTE/3GPP technologies such as CAT-M1. Whereas NB-IoT operates at 180kHz to 200kHz, CAT-M1 operates at 1.4 MHz and can achieve up to 1Mbps throughput. CAT-M1 modems often claim support for NB-IoT.

Designed primarily for connecting low-power stationary sensors, NB-IoT offers wide coverage and strong indoor penetration. Compared to LoRaWAN, NB-IoT provides slightly higher peak throughput of 60Kbps, according to an Ubidots report and 250Kbps peak per this Ericsson blog report. NB-IoT also offers slightly lower latency and provides superior 256-bit 3GPP encryption.

NB-IoT consumes more power at 120mA peak current compared to 32mA for LoRaWAN. Generally, LoRaWAN is more common on large campuses, farms, and industrial sites where the owner sets up its own LoRaWAN infrastructure. NB-IoT is more typically found in scenarios where LPWAN connections are needed with other institutions and public networks.

 
Further information

No pricing or availability information was provided for the SRG-3352C, although it will likely appear on the Aaeon eShop at some point. More information may be found in Aaeon’s announcement and product page.