The circuit discussed in my last two posts already has some intelligence of its own. The TP4057 charge control IC switches between constant current and voltage mode as the lithium cell increases in charge, and the DW01AM over- and discharge protection IC disconnects the battery's negative terminal from the rest of the circuit in the event that its voltage drops below 2V, or if the charge voltage rises over 4.3V.
As part of the Energy Brain I want the ATtiny uC to monitor the Li-Ion cell and the super-capacitor voltage. When either drops below a certain level, the ATtiny communicates on an interrupt line with the uC in the Memory & Learning Brain and lets it know what's up. The Memory & Learning Brain can then decide what to do with that information; to initiate a recharge of the super-capacitor, to communicate a request for solar charge to the outside world, to alter sensing and communication behavior in ways that conserve energy, or to send other Brains into sleep mode.
What I'm trying to mimic here is the connection between the biological gut and brain; the involuntary sensation of hunger or exhaustion, and the intentional decision to eat, sleep, or forage for food.
I spent some time mapping the Li-Ion charging circuit I purchased. As far as I can tell the circuit is a combination of the reference design for each of the integrated circuits - U2, U3, and U4 - and an RC filter. My guess is that the RC filter is supposed to keep the noise from the DC/DC converter from interfering with the current monitoring of the lithium cell charging IC.
The next step is to evaluate the best way to interface an ATtiny85 to monitor and control the circuit.
