Embedded Linux

Compiling U-Boot with Device Tree Support for the Raspberry Pi

October 5, 2018 Craig Peacock 11

U-Boot U-Boot (The Universal Bootloader) is a popular, feature rich, open source bootloader for embedded systems. It is licenced under the GNU General Public Licence version 2. While its primary purpose is to boot an operating system, such as Linux, it also provides many useful tools for developing and debugging embedded systems. This includes support for many common file-systems including FAT, ext3, ext4, NFS etc and interfaces such as USB, Ethernet (IP), MMC and even Asynchronous Serial (Kermit/xmodem/ymodem). This allows the developer to load new images and file-systems from a variety of sources for testing and/or reflashing. It also includes …

LoRaWAN

RN2903: Using the LoRaWAN™ Library Plug-in for MPLAB® Code Configurator and customising for the AU915 Frequency Plan

September 19, 2018 Craig Peacock 5

The RN2903 Wireless LoRa Module from Microchip ships with an on-board LoRaWAN Class A protocol stack. This stack can be accessed via ASCII based commands over a UART interface. For many, this is the interface of choice, offloading the complexity of the LoRaWAN stack to a dedicated processor contained within the module. Another advantage is Microchip can fully certify the module and stack. I decided not to use the on-board stack for two reasons: Here in Australia, we must use the AU915 frequency plan. Microchip has beta firmware for this frequency plan, but it is not yet publicly available. Developers …

LoRaWAN

Microchip RN2903 LoRa Transceiver Breakout Board

September 15, 2018 Craig Peacock 4

A breakout board for Microchip’s series of LoRa transceiver modules: RN2483 fully-certified 433/868 MHz Module (Europe) RN2903 fully-certified 915 MHz Module (North America, Australia) The RN2483/RN2903 LoRa modules contain a Microchip PIC18LF46K22 MCU with a Semtech SX1276 radio transceiver and is intended as a complete certified solution with LoRaWAN Class A protocol stack and an ASCII command interface over a UART connection. However, if you want to get under the hood, MicroChip provide details in the LoRaWAN Library Plug-in for MPLAB Code Configurator User’s Guide on how to target the on-board PIC18LF46K22 and customise the module for your own purposes. RN2903 Pin Out (XLSX) Design Files …

Power

ML2032 Coin Cell Charger

September 13, 2018 Craig Peacock 0

This design is intended to recharge Maxell ML2032 Lithium Manganese Dioxide rechargeable coin cell batteries with a nominal voltage of 3.0V. These are ‘special’ coin cell batteries designed specifically as a rechargeable secondary cell. It is not recommended to attempt to recharge a primary CR2032. These cells have not be designed for recharging.  Background Rechargeable replacements of the popular CR2032 3V lithium coin cell battery exist, but one caveat is reduced capacity. The common CR2032 from name brand manufacturers such as Panasonic will have a capacity of approximately 220mAh. Rechargeable replacements of the CR2032 appear to come in a range of different chemistries. …

LoRaWAN

RAK833/RAK2247 LoRaWAN Concentrator

August 29, 2018 Craig Peacock 9

This board is a Raspberry PI Hat for the RAK833/RAK2247 LoRa Concentrator Gateway Modules. The RAK2247 is improved version of the RAK833 with better heatsinking, a boost in the maximum transmission power and improved interference immunity. Both are a smaller version of the popular RAK831. The RAK831 is larger, about the same footprint than a Raspberry PI and requires a breakout board to convert the RAK831’s 24 pin connector to the Raspberry PI’s 40 pin connector. The RAK833 is a more elegant industry standard PCI Express Mini Card form factor (Type F2). The RAK833 module consists of a Semtech SX1301 Digital Baseband chip …

Power

12V 7Ah SLA Low Voltage Disconnect

June 12, 2018 Craig Peacock 0

The 12V 7Ahr “alarm” battery is still a safe, dependable choice for stationary back-up supplies, running items such as LED lighting or modem/routers. Using two Keystone 3571 female PCB terminals, this PCB assembly attaches directly to the terminals of a 12V 7AH SLA Battery (with 4.75mm spade terminals) and provides a low voltage cut-out to protect the battery, and a fuse to protect wiring. The Maxim Integrated MAX8212 Micro-power Voltage Comparator with 1.15V reference switches a high side P-Channel MOSFET to disconnect the load. The MOSFET has a low on resistance of 4.1mOhms and a maximum current capability of 90 Amps well exceeding that of the battery. The …

Electronics Hardware

Review: LTC3780 Sync Buck Boost DC-DC Converter

July 30, 2015 Craig Peacock 0

Prevalent on ebay and Amazon is the “LTC3780 Automatic lifting pressure constant voltage step up step down 10A 130W” DC to DC Converter. (What a mouthful) I’m not quite sure what the “Automatic lifting pressure” is about (suspect Chinglish), but it is a fairly well designed DC-DC switcher based on Analog’s (formally Linear Technology) LTC3780 – High Efficiency, Synchronous, 4-Switch Buck-Boost Controller. The board sells for a bargain basement price of about $20 to $25 USD. My interest in this DC-DC switcher is to operate 19VDC laptops/notebooks and LCD TVs from 12V batteries/solar. I took the plunge and purchased two units. Here are …