Arnolde
Thanks for your comments.
I got over the interrupt problem by preserving the value obtained from the previous adc conversion loop and using that when an interrupt occured. So it's actually using the previous adc result after an interrupt. As it loops so quickly this doesnt matter.
I though about a big board but it sounded a nightmare and would be massive for 50 or 100 slaves. It may be the way to go though, feel free to knock one up based on the overall design if you wish.
![Wink :wink:](./images/smilies/icon_wink.gif)
In your setup there would be 200 wires
![Shocked :shock:](./images/smilies/icon_eek.gif)
going from the giant slave board to the pack. In the current setup with individual slave boards there are only four wires from the pack to the Master. I like the individual boards as the visual indications they also provide is there on top of the cell in question, so you can see what's happening.
One of the reasons the Master is limited to 128 cells is due to the amount of available Pic scratchpad ram which is 128bytes, this is used to store the incomming serial voltage data from the Slaves and keep execution speed up to a reasonable level.
The total pack voltage is then calculated by adding all the values stored in the scrathpad ram together. This could be removed but calculations would have to then be done on the fly, inbetween serial transmissions from each slave, slowing the data stream probably, but meaning you could have an unlimited number of cells in the pack. The Pic I'm using the Picaxe 28X1 has an upgrade comming soon (28X2)with 256 bytes of ram which would allow 256 cells using my current software design. Again feel free to try the on the fly approach by modifying the software and see how fast it works, I will probably do this later on my 50 cell pack, so we can get an idea of the speed using the two approaches. Remember the Master software is still untested and very much in alpha form, so a comlete change of direction as to the way it calculates/operates could happen at any time. The speed taken to poll the pack would simply increase as more cells are added, my design criteria were that it should poll the pack once per second ish
I've already bought some expanding foam for the battery tray issue
Regards Peter