Can someone explain all of the technical reason(s) why a kegboard pro mini can’t support more than 2 taps? The hardware is certainly fast enough to handle interrupts from 4 inputs that have a 2 KHz max signal speed. The software seems to be able to support it too with some minimal changes.
If it is possible, then it’s just a matter of wiring to some free ports to a connector, that’s no big deal for me.
Sure:
Only INT0 and INT1 are brought out from the AVR. Interrupts 2 and 3 exist on the AVR but unfortunately are not connected to anything.
In order to work properly, flow meter inputs also need (a) a pull up resistor and (b) an RC filter. Again these are only populated for the two interrupts.
If we spin another revision, this will be fixed, unfortunately we didn’t catch it soon enough.
Mikey,
Just double checking. So if we were to buy just one KBPM we COULD use it on the 4 tap system without problems like missing pulses? Getting and wiring a pull-up resistor per port and and RC filter are not a problem for us at all. Are they identical to something else on the existing ports? Is the schematic available?
When will the KBPMs be available to everyone again? I am trying to get one for my son on his 4 tap system for Christmas and if we can only get one KBPM or make an equivalent Arduino in time, we are looking for an alternative that will work. Getting parts and doing fine wiring/soldering is not a problem at all, we just don’t have a lot of hands on experience with these devices.
So if we were to buy just one KBPM we COULD use it on the 4 tap system without problems like missing pulses?
Unfortunately no, not easily. INT2 and INT3 are the best choices, but they are not brought out from the AVR (so you’d have to do some rework to attach small gauge wire directly to the pads). You might be able to make use of some of the pins that are exposed – but you’d need to write a pin-change interrupt handler (since they are not dedicated external interrupts).
I’ll dig up the schematic and post it, we must have overlooked doing that during the kickstarter (and nobody asked!)
When will the KBPMs be available to everyone again?
They’re back in stock now, sorry for the misleading copy on the store page (fixed!)
If you’re comfortable soldering and doing some DIY work, a reasonable alternative to using KBPMs might look something like this:
- Get an Arduino Leonardo (very similar to KBPM)
- Wire pull-ups and RC filters to INT0-INT3
- Connect meters accordingly
- Flash kegboard firmware (add ISRs for INT2 and INT3 as needed).
cheers,
mike
Let me know when you post the schematics that you mentioned.
Mikey,
I looked the schematics for the kegboard and kegboard alt (main board and coaster) and I don’t see any RC filters.
I see some pullups on flow A & B (2.2k) and Onewire A & B (4.7k).
I just see a general 0.1 uf power supply filter cap, but not anything in RC combination as a filter.