A brief update on this project:
1. That's how the final version is looking like... a few extra components from the original design. The power supply (right side) ended up being quite busy with some extra circuits!
2. Everything is going as planned: the
board is in Production and delivery should start well before planned date.
3. Manage to get down to
3.7uA average consumption when everything is at sleep when powered by 2xAA (3V). When powering from 1xAA (1.5V) the sleeping consumption goes to 5.4uA.
4. The MCP16251 step-up power regulator proved to be very efficient as well. Getting around
90% efficiency when tested with a
100R load and the board being powered by a
1.5V source, stepping-up to 3.3V.
As we all know, batteries are likely to drop its voltage along the life, especially Alkaline ones. The tests showed that the board was able to keep running under very low input voltage. For example, with the same
100R load and a
input voltage of 0.8V the regulator was doing
over 75% efficiency and outputting 3.25V. For the sleeping testing, the consumption was
well under 9uA when powered by 0.8V.
5. A few extra components can be soldered to the back of the board by the user, depending on individual needs. Like a RTC, a 1117 LDO or a CR2032 battery holder.
6. For the ones interested on the software. The MCU will be shipped with a modified bootload, capable of performing firmware update from the external SPI Flash, which can be easily used to do over-the-air upgrades. Also a
"Factory reset" is possible, putting the board to it's factory firmware and ready to
receive new software over-the-air. The idea is to have a board which could be programmed and never needs to be connected to a computer (of course you'll need at least two boards for that to work).
More details at:
https://talk2.wisen.com.au/product-talk2-whisper-node-avr/https://bitbucket.org/talk2/whisper-node-avr/overviewCheers,