FreeCalypso > hg > freecalypso-docs
comparison FC-handset-spec @ 49:38bcb9425df0
FC-handset-state: battery documented
| author | Mychaela Falconia <falcon@freecalypso.org> |
|---|---|
| date | Fri, 11 Jun 2021 04:34:26 +0000 |
| parents | cb8d43a5023c |
| children | da1a2a32c260 |
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| 48:cb8d43a5023c | 49:38bcb9425df0 |
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| 678 to be made right now. | 678 to be made right now. |
| 679 | 679 |
| 680 Because our firmware will be designed for a simple on/off vibrator control, | 680 Because our firmware will be designed for a simple on/off vibrator control, |
| 681 during fw development on the Venus board it will be trivial to use a LED to | 681 during fw development on the Venus board it will be trivial to use a LED to |
| 682 simulate the vibrator on/off state. | 682 simulate the vibrator on/off state. |
| 683 | |
| 684 1.10. Battery | |
| 685 | |
| 686 The battery in our FC Libre Dumbphone handset will be single-cell Li-ion. It | |
| 687 goes without saying that this battery will be freely removable and replaceable | |
| 688 by end users. The specific size, form factor and mAh capacity of this battery | |
| 689 won't be addressed until later in the project, when we get closer to building | |
| 690 the actual handset. | |
| 691 | |
| 692 Our Calypso+Iota chipset dates from the era when the cellular handset industry | |
| 693 was transitioning from NiMH to Li-ion batteries, and the Battery Charger | |
| 694 Interface (BCI) block in the Iota chip supports both battery types, or at least | |
| 695 TI's documentation claims so. Given that we are going against the mainstream | |
| 696 society's ideas in so many other ways, I have given thought to the possibility | |
| 697 of using a NiMH battery instead of Li-ion. However, the problem with using a | |
| 698 NiMH battery is that we would be going into completely uncharted territory | |
| 699 without any guidance. In the case of Li-ion batteries the charging process is | |
| 700 well-understood in both theory and practice, and our FCHG logic based on reverse | |
| 701 engineering of Pirelli's firmware works well both on the same Pirelli and on | |
| 702 Motorola C1xx family. In contrast, if we went with NiMH, we would have | |
| 703 absolutely no guidance in implementing the necessary charging control logic | |
| 704 (TI's LCC code is useless), causing a huge risk to the project. Furthermore, | |
| 705 determining the state of charge from Vbat for the purpose of the bars icon is | |
| 706 already somewhat challenging even with Li-ion, given the relatively flat middle | |
| 707 part of the discharge curve - and with NiMH we can only expect the problem to be | |
| 708 even worse, as their discharge curve is said to be even flatter. For these | |
| 709 reasons, we are going to play it safe and stick with Li-ion. |