August 2023
Alex presented the following tool tips (see https://thehardcoder.weebly.com/tooltips)
Improved non-blocking delay: non-blocking Arduino delay code which compares time duration rather than timestamps. The millis() function overflows every 50 days and timestamp comparison will fail.
Easy SMD desoldering: use 2 soldering irons to remove SMD components easily.
Wireless surround speakers: low-latency use bluetooth transmitter/receiver to send audio signals to surround speakers.
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Andrew Allen presented:
Very simple low speed networking of microcontrollers:
Two core bell wire can be used over a few tens of metres to provide all power and data transmission at 9600 baud by simply providing each microcontroller with a transistor switch and resistor to pull extra current.
With resistor values used (180ohms) and a total of 8 controllers this gave around a one volt drop in the power/data line which is easily sensed by any of the controllers via a resistive divider. The voltage at the input pin used must always be less than 5v which is the supply voltage for all controllers as each is feed by its own three pin 5volt regulator also connected to the power/data line.
The concept uses a nominal 9volt supply provided by a LM317T connected as current limiting regulator. This power/data line is allowed to vary from 9 volts down to 7 volts as more current is taken. Firmware in the controllers implements a TDM (time division multiplex) system to share this one core which thus carries all data and power.
One of the controllers acts as master at any one time. When using low end microcontrollers to typically collect only one or two types of data from transducers, a lot of resources and input pins are left unused in each controller. This networking method makes use of these unused functions and pins and requires very little in the way of extra components, just a few resistors and one transistor per controller.
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Martin from Germany showed his accelerometer-based implementation of a motion controller that can be head-mounted for people with disabilities to control the mouse cursor in Windows. We also had nice views of the place he was staying and the street outside. Sky was overcast and grey which was apparently the standard weather for Germany.