Category Archives: Uncategorised

Turn a TI Launchpad into a GoodFET with just a Serial Cable

lp_bsl_modThe TI MSP430 Launchpad is a cheap MSP430 development board – about £3 when they first came out, although a bit more now.  I think mine was a freebie from a distie.  Although I quite like the MSP430 I do tend to use either AVR or some kind of ARM for most of my projects, so it hasn’t really seen much use.

The built-in emulator consists of a TUSB3410 and an MSP430F1612, pre-programmed with TI’s own MSP430 “FET” debugger.  My aim here is to end up with a debugger that I can use with TI’s CC1110 chips used in the Ciseco SRF.  The GoodFET project can talk to these using its Chipcon module, and this has at some point in the past been made to run on the Launchpad.

Continue reading

RFM22B/23B Availability and RFM69W

There is a degree of uncertainty at the moment regarding the future availability of HopeRF’s RFM22B and RFM23B modules.  Having been in touch with a number of HopeRF’s European distributors the message appears to be that while they are indeed “not recommended for new designs”, there has been no end-of-life notification for either of these products.  Both modules will continue to be available for the foreseeable future, although they may be subject to minimum order quantities once distributor stocks run dry.

Recommended replacements are the RFM69W and RFM69HW.  These new modules appear to be based on Semtech SX1231H, which means they are not an ideal equivalent because of a 2.4 V minimum Vcc (the RFM23B can work down to 1.8 V).  Fingers crossed that HopeRF has actually used the 1.8 V capable non-H version of the chip on the lower power RFM69W.

Several EU distributors have indicated that they will be carrying the new modules within a month or so.  Pricing looks like it will be slightly cheaper than that of the older modules, so that plus the addition of hardware AES should make these a welcome upgrade.

Timestore – a Time Series Database

As part of my interest in IoT and Home Automation I spent some time looking for a non-destructive alternative to rrdtool for long-term storage and aggregation of sensor data.  The search did turn up a few alternatives, particularly OpenTSDB, but I was not especially impressed with its performance nor its complexity.  During the search I came across Flot, which is a JavaScript library for plotting graphs client-side in a browser, and the idea for a “Web2.0” time-series database was hatched.

Timestore, which is the result, is written in C and accessed via an HTTP API that can feed data series directly to Javascript via AJAX calls.  It is designed to be lightweight, fast, and to retain all data.  Like most equivalent tools it can decimate on inserts, so queries for aggregate data take constant time regardless of the time-scales involved.

The design has optimisations for sensor applications, where a single device may report multiple data items at each time point.  These can be submitted in one go, but queried as separate series for display.  The modular architecture will enable alternative access methods to be added; MQTT being an obvious one which I intend to look into for data submission.

Code and documentation can be found on the project’s dedicated page.  There are some hosted examples to play with, including the graph embedded above, which is real temperature data and can be zoomed by dragging a box around a range.  Double-click to zoom back out.  The software is released under GNU AGPLv3.