USB narrowband transceiver - Page 1
Forum section: electronics / projects

author: Velocitus
author_rank: Newbie
timestamp: October 15, 2016, 08:05:23 pm
content: Hello,I would like to present a little project with aim of getting some feedback.I'm working on various "Internet of Things" devices that cooperate in wireless sensor network.Usually they communicate using narrowband transceiver operating in ISM band (868MHz here in Europe).One of the devices is an RF transceiver, which serves as data collector and interface to computer.This device is essentially a USB key that connects to PC as a virtual COM port and relays data between the port and RF spectrum (half duplex).Radio part consists of CC1120 transceiver and CC1190 amplifier from Texas Instruments.The device had few versions with various ICs configurations.( see first photo )Versions from Left to right (oldest to newest):1. MSP430 + CC11202. MSP430 + CC1120 + CC11903. FT234XD + STM32F0 + CC1120 + CC1190Old versions ran with MSP430 controller using USB stack from TI.This however required installation of custom driver on PC and took half of available program space in MCU Flash.The newest version has FTDI chip for compatibility and STM32F051 as controller.Non-optimised range of CC1120 WITHOUT the amplifier is about 175meters at 1kpbs with 25khz bandwidth.With the RF amplifier the range goes up to 500m at 5kpbs with 25khz BW.(Not quite relevant range reference I know :-) More testing to be done. )The CC1120 and CC1190 combo is expected to have 500mW TX power which is maximum allowed in EU ISM bands without license.Together they can support 868MHz band or 915Mhz. Standalone CC1120 can however do 433MHz or 169MHz.I'm using the CC1120 transceiver, as it has the most data-link improving features. (or maybe I haven't seen enough of RF ICs)It is more expensive than competitors, but the features (like minimal 8KHz bandwidth) are worth it for slow long range link.I'm considering selling the newest version of these devices as programmable RF transceiver.( see second photo )So far I have not found user-programmable USB RF transceiver.Such device allows user to take advantage of physical layer properties that are otherwise limited by higher level software.( like the ability to program custom protocol, use less common modulations, efficiently use received signal strength etc. )Since controller is from STM, user would need SWIM programmer for debugging. ( standard development kit would do )Device works on Windows and Linux including single-board computers. ( tested with raspberry 3 and A20-olinuxino-lime )Device would be supported with software samples guiding user through necessary initializations.I have developed simple chat application which would be open and come pre-programmed in devices, so user-programming would not be absolutely necessary.All together this allows various applications : home/greenhouse automation, radio location, long range control, remote data collection etc.My few questions for you are:- Would such device interest you?- Would you prefer integrated ceramic/PCB antenna or rather SMA connector?- Would you see CC1120 sufficient without the amplifier with range limited to 200m?- Is it rational to seek crowdfunding for this kind of stuff?Thank you :-D