FreeCalypso > hg > freecalypso-schem2
comparison minnie/doc/Design-spec @ 98:3ab69117b09f default tip
minnie/doc/Design-spec: finished in the first pass
| author | Mychaela Falconia <falcon@freecalypso.org> |
|---|---|
| date | Sun, 01 Oct 2023 08:17:05 +0000 |
| parents | 269b330ac428 |
| children |
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| 97:269b330ac428 | 98:3ab69117b09f |
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| 332 strings, allowing the board to be recognized among other USB devices sharing | 332 strings, allowing the board to be recognized among other USB devices sharing |
| 333 the same VID:PID. | 333 the same VID:PID. |
| 334 | 334 |
| 335 2.5. RF plumbing | 335 2.5. RF plumbing |
| 336 | 336 |
| 337 The RF interface on FC Tango module is a microcoaxial connector of a type | |
| 338 compatible with Hirose U.FL and Sunridge MCB2 series, but a GSM MS development | |
| 339 board needs to bring out its RF interface on an SMA female connector. The plan | |
| 340 for FC Minnie is to use the same approach as was successfully implemented on | |
| 341 FC Caramel2: a microcoaxial cable assembly from Sunridge that goes from an | |
| 342 MCB2G plug to an SMA connector that has PCB mounting legs only for mechanical | |
| 343 securement and grounding, while the RF signal never passes through the main PCB. | |
| 344 | |
| 337 2.6. SIM socket | 345 2.6. SIM socket |
| 338 | 346 |
| 347 The SIM 2FF socket on FC Minnie will be of the same hinged type as featured on | |
| 348 FCDEV3B and Caramel2 boards. The placement and orientation of this socket on | |
| 349 the board will need to be chosen so that it will work conveniently with SIMtrace | |
| 350 FPC cables; FCDEV3B is good in this regard, but Caramel2 is not. | |
| 351 | |
| 339 2.7. Analog audio | 352 2.7. Analog audio |
| 340 | 353 |
| 354 Only the main analog audio channel will be brought out, not auxiliary. The main | |
| 355 audio channel will be brought out on a 2.5 mm TRRS jack in the pinout that was | |
| 356 originally established by iWOW with their DSK and has since been adopted by | |
| 357 FreeCalypso, same as on FC Caramel2. FreeCalypso HQ has a large batch of | |
| 358 FC-HDS4 headsets that have been custom-made for us in this pinout, hence it | |
| 359 makes no sense to implement any other arrangement. | |
| 360 | |
| 341 2.8. Digital audio | 361 2.8. Digital audio |
| 342 | 362 |
| 363 Calypso MCSI is a PCM interface to the DSP part of Calypso that can be | |
| 364 configured (using the standard facilities of DSP ROM code plus TI's official | |
| 365 patches) to carry digital voice during calls, in 13-bit linear PCM sample | |
| 366 format, 8000 samples per second. This interface was first brought out and | |
| 367 experimented with on FCDEV3B, but it is also brought out on FC Tango module. | |
| 368 This interface will be brought out on FC Minnie board on a 5-pin header, in the | |
| 369 same pinout as on FCDEV3B. | |
| 370 | |
| 371 The Mother of FreeCalypso has a plan to produce a gateware design for the common | |
| 372 Lattice iCEstick FPGA board that will turn this Icestick into an interface | |
| 373 adapter for Calypso PCM voice, ferrying digital PCM samples to and from a Linux | |
| 374 host by way of FT2232H UART channel on the Icestick itself. In this plan the | |
| 375 PCM interface will be connected with jumper wires directly from the Icestick | |
| 376 board to the MCSI header on FCDEV3B, FC Minnie or FC Caramel2. | |
| 377 | |
| 378 3. Production notes | |
| 379 | |
| 380 3.1. Manufacturing and test process overview | |
| 381 | |
| 382 FC Minnie boards will be assembled at Technotronix in Anaheim, California, USA | |
| 383 and then production-tested at FreeCalypso HQ. The assembly performed at | |
| 384 Technotronix will include permanent mounting of a Tango module onto each Minnie | |
| 385 board, whereas the subsequent production test process at FreeCalypso HQ will | |
| 386 include the following steps: | |
| 387 | |
| 388 * FT2232H EEPROM programming; | |
| 389 * Loading FreeCalypso firmware into Tango module flash; | |
| 390 * Preening FFS for FC Tango firmware and for FC Minnie pinmux config; | |
| 391 * Testing the GSM RF tract in all 4 bands with a CMU200; | |
| 392 * Testing the SIM socket by inserting an FCSIM1 card and verifying correct | |
| 393 SIM communication; | |
| 394 * Testing the analog audio interface by inserting an FC-HDS4 headset and | |
| 395 commanding the firmware to generate a beep; | |
| 396 * Other minor hardware tests as feasible. | |
| 397 | |
| 398 3.2. Permanent coupling of Minnie board and Tango module | |
| 399 | |
| 400 FC Tango modules are not meant to be casually swappable once mounted on an | |
| 401 application board such as FC Minnie: | |
| 402 | |
| 403 * The module features 4 grounding legs which must be soldered; these grounding | |
| 404 legs are essential, as they carry power supply return current during GSM Tx | |
| 405 bursts. The need for soldering and desoldering should already be seen as a | |
| 406 deterrent to casual (unnecessary, just for the heck of it) module swapping, | |
| 407 but given that many hackers have absolutely no difficulty with soldering, | |
| 408 other factors should be considered too: | |
| 409 | |
| 410 * The fine-pitch board-to-board connector with 80 pins is extremely delicate, | |
| 411 and can be easily damaged by unnecessary mating and unmating cycles; | |
| 412 | |
| 413 * The microcoaxial connector for the RF interface is likewise very delicate and | |
| 414 subject to the same considerations. | |
| 415 | |
| 416 If a *legitimate* need to remove and replace the Tango module does arise (for | |
| 417 example, if some component inside the module goes bad and you need to either | |
| 418 repair or replace the Tango module), it can certainly be done - but it should | |
| 419 NOT be done casually, just for the heck of it. |