Sara rx ab

SARA-Rx application board

SARA-R4 NB-IoT + Cat-M1 + GNSS application board - NINA-B3 with Secure MQTT

:heavy_exclamation_mark:BEFORE YOU DO ANYTHING, CHECK BATTERY POLARITY:heavy_exclamation_mark:

TODO

• More details about battery etc...
• !!! Better Socket close URC handler.
• Check AT response based on the last chars, in order to avoid missing URCs when after "OK" for example
• Implement Subscribe;

Energy Budget

• 88mA active current;
• Code takes ~10 seconds to execute;
• Wakes every hour;
• 40uA Sleep current;
• 10 hours of light available;
• V charge ready = 3.67V;
• V Over discharge = 3.6V;
• V Over charge = 4.12V;

Source Power Required = 3.8mW

Storage Required = 4.73mAh

Sleep Current

Nordic SDK

• This is based on nRF5_SDK_16.0.0_98a08e2, get yours here: https://www.nordicsemi.com/Software-and-tools/Software/nRF5-SDK/Download

1. Sign in to the AWS IoT Console
2. Register a Device in the Registry
3. Configure Your Device
4. View Device MQTT Messages with the AWS IoT MQTT Client

https://docs.aws.amazon.com/iot/latest/developerguide/iot-gs.html

• 120mA active current;
• Code takes 15 seconds to execute;
• Wakes every hour;
• 2mA Sleep current This needs to be optimized;
• 10 hours of light available;
• V charge ready = 3.67V;
• V Over discharge = 3.6V;
• V Over charge = 4.12V;

1. Clone this repo to a local folder > git clone https://github.com/ldab/SARA-Rx-application-board
2. Point the $(SDK) @./code/ninab3/blank/ses/libuarte_pca10056.emProject to where you have installed Nordic SDK, for example C:\nRF\nRF5_SDK_16.0.0_98a08e2
3. Like so: macros="CMSIS_CONFIG_TOOL=C:/nRF/nRF5_SDK_16.0.0_98a08e2/external_tools/cmsisconfig/CMSIS_Configuration_Wizard.jar;SDK=C:/nRF/nRF5_SDK_16.0.0_98a08e2"
4. Open the SEGGER Embedded Studio project file located in ./code/ninab3/blank/ses/libuarte_pca10056.emProject

• PS. don't forget to set the NFC Pins as GPIO on the Preprocessor: CONFIG_NFCT_PINS_AS_GPIOS

Ref. https://devzone.nordicsemi.com/f/nordic-q-a/44638/how-to-move-an-sdk-example-out-of-the-sdk-tree

IoT Dashboard

• Adafruit https://io.adafruit.com provides a free MQTT broker with a Dashboard allowing this project to be displayed publicly with little to no effort

  • Create an account and insert your KEY as the MQTT_PASS
  • MQTT_USER is the username used for creating the account.

• Adafruit expect data as a json, for example:

  sprintf(_msg, "{\"feeds\": {\"T\": %.01f,\"H\": %.01f,\"Bpc\": %d,\"RSRP\": %.02f,\"Bv\": %.02f}}",
          temperature, humidity, batt_lvl_in_percentage, modemInfo.RSRP, _b)

• The topic, groups and feeds are created automagically, on the example the MAC address is added as an identifier:

  sprintf(topic, "lbispo/g/nina_%X/json", NRF_FICR->DEVICEADDR[0]);

https://io.adafruit.com/lbispo/dashboards/moree?kiosk=true

Efficiency

Schematic

PCB

BOM

Enclosure

Kown issues, limintations

• MQTT Socket Implementaition can only publish QoS 0 messages.

Thoughts or Improvements

• Use STATUS 2 of AEM10941 as last grasp;
• Control boost converter EN, in order to turn SARA Off;
  • Remove boost converter, as it does not boost a lot since Vbatt ON = 3.6V.
• SARA RESET Pin access;
• Use 101b AEM10941 Configuration in order to Vovdis = 3.0V givin extra ~20% battery (?).
• Open Drain 74LVC3G07 buffer on NINA LED, in order to avoid leakage.

Credits

• MQTTBox for Windows in order to communicate with the broker and check messages;
• CloudMQTT Free Cloud Broker;
• MQTT implementation inspired and based on knolleary PubSub Client;
• AT Commands implementation inspired on vshymanskyy TinyGSM;
• GitHub Shields and Badges created with Shields.io;