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FC-handset-spec section 1.7.1: mention Pirelli DP-L10
author Mychaela Falconia <falcon@freecalypso.org>
date Tue, 15 Jun 2021 19:28:52 +0000
parents 4389cd2b9d02
children 153b517ccc7a
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63:4389cd2b9d02 64:6b02de926277
479 479
480 1.7.1. Earpiece and loudspeaker separation 480 1.7.1. Earpiece and loudspeaker separation
481 481
482 Most current mainstream phones (in fact, all that I am familiar with) have 482 Most current mainstream phones (in fact, all that I am familiar with) have
483 physically separate speaker transducers for the earpiece function (hold up to 483 physically separate speaker transducers for the earpiece function (hold up to
484 ear to talk) and the loudspeaker+ringer function. The earpiece speaker is a 32 484 ear to talk) and the loudspeaker+ringer function. The not-so-current and not-
485 ohm load, and the loudspeaker is an 8 ohm load. In a Calypso+Iota design, an 485 so-mainstream Pirelli DP-L10 also features the same arrangement. The earpiece
486 external amplifier chip is needed to drive the 8 ohm loudspeaker, whereas the 486 speaker is a 32 ohm load, and the loudspeaker is an 8 ohm load. In a
487 little 32 ohm earpiece speaker can be driven directly by Iota EAR output. 487 Calypso+Iota design, an external amplifier chip is needed to drive the 8 ohm
488 loudspeaker, whereas the little 32 ohm earpiece speaker can be driven directly
489 by Iota EAR output.
488 490
489 However, a very different design was implemented by TI on their D-Sample and 491 However, a very different design was implemented by TI on their D-Sample and
490 Leonardo boards. They have only one speaker, one of 8 ohm kind, that is 492 Leonardo boards. They have only one speaker, one of 8 ohm kind, that is
491 physically mounted in the position where the earpiece speaker would normally go. 493 physically mounted in the position where the earpiece speaker would normally go.
492 In order to not overwhelm the user's ear in handheld operation, they have 494 In order to not overwhelm the user's ear in handheld operation, they have
505 507
506 For our own FC Libre Dumbphone, I am going with the separate speakers 508 For our own FC Libre Dumbphone, I am going with the separate speakers
507 architecture, using physically separate earpiece and loudspeaker transducers. 509 architecture, using physically separate earpiece and loudspeaker transducers.
508 This architecture feels more native to me, and it will allow for independent 510 This architecture feels more native to me, and it will allow for independent
509 tuning of the two audio paths. In my defense, all current mainstream phones 511 tuning of the two audio paths. In my defense, all current mainstream phones
510 seem to use the same architecture - the other approach with a single loudspeaker 512 seem to use the same architecture, and so does the Pirelli phone that serves as
511 in the earpiece physical position seems very uncommon. 513 my personal reference - the other approach with a single loudspeaker in the
514 earpiece physical position seems very uncommon.
512 515
513 1.7.2. Loudspeaker implementation 516 1.7.2. Loudspeaker implementation
514 517
515 The external amplifier chip for driving the 8 ohm loudspeaker will be TI 518 The external amplifier chip for driving the 8 ohm loudspeaker will be TI
516 TPA6203A1, copied from Leonardo schematics and proven good on FCDEV3B. On 519 TPA6203A1, copied from Leonardo schematics and proven good on FCDEV3B. On