FreeCalypso > hg > freecalypso-docs
comparison FC-handset-spec @ 88:91352355857c
FC-handset-spec: document beyond-USB rescue provisions on FC Venus
author | Mychaela Falconia <falcon@freecalypso.org> |
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date | Fri, 15 Apr 2022 05:59:36 +0000 |
parents | 78d4d362c086 |
children | b10442b756b2 |
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87:78d4d362c086 | 88:91352355857c |
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1505 3.3.2. USB subsystem | 1505 3.3.2. USB subsystem |
1506 | 1506 |
1507 Our Venus development board will include the same USB subsystem as intended for | 1507 Our Venus development board will include the same USB subsystem as intended for |
1508 the final FC Libre Dumbphone handset, as described in sections 1.11 and 1.12, | 1508 the final FC Libre Dumbphone handset, as described in sections 1.11 and 1.12, |
1509 consisting of a USB mini-B interface connector, a charging on/off switch with | 1509 consisting of a USB mini-B interface connector, a charging on/off switch with |
1510 the charging circuit behind it, and the FT2232x subsystem of section 1.12. | 1510 the charging circuit behind it, and the FT2232D subsystem of section 1.12. |
1511 | 1511 |
1512 This design is a radical departure from our previous development boards which | 1512 This design is a radical departure from our previous development boards which |
1513 bring out the two Calypso UARTs in their raw LVCMOS form, leaving the USB | 1513 bring out the two Calypso UARTs in their raw LVCMOS form, leaving the USB |
1514 interface to an external adapter, most recently our own DUART28. In fact, the | 1514 interface to an external adapter, most recently our own DUART28. In fact, the |
1515 Mother's original idea for the Venus board was to keep essentially the same | 1515 Mother's original idea for the Venus board was to keep essentially the same |
1557 (with standard USB as the charging power source) can be made a part of the | 1557 (with standard USB as the charging power source) can be made a part of the |
1558 demo. | 1558 demo. |
1559 | 1559 |
1560 3.3.2.1. Linux kernel patch requirement | 1560 3.3.2.1. Linux kernel patch requirement |
1561 | 1561 |
1562 The FT2232x USB subsystem implemented on FC Venus will include the boot control | 1562 The FT2232D USB subsystem implemented on FC Venus will include the boot control |
1563 feature originating from DUART28C, as described in section 1.12.3. This | 1563 feature originating from DUART28C, as described in section 1.12.3. This |
1564 hardware feature has an implication for developer-users of this board: anyone | 1564 hardware feature has an implication for developer-users of this board: anyone |
1565 wishing to play with a Venus board beyond already-flashed fw (i.e., anyone | 1565 wishing to play with a Venus board beyond already-flashed fw (i.e., anyone |
1566 wishing to connect the board to a host computer) will need to apply our DUART28C | 1566 wishing to connect the board to a host computer) will need to apply our DUART28C |
1567 support patch to the ftdi_sio driver in their Linux kernel; as for other host | 1567 support patch to the ftdi_sio driver in their Linux kernel; as for other host |
1584 to show proof that they have applied this maintainer-rejected patch as a | 1584 to show proof that they have applied this maintainer-rejected patch as a |
1585 condition of receiving their board. | 1585 condition of receiving their board. |
1586 | 1586 |
1587 3.3.2.2. Board bring-up order | 1587 3.3.2.2. Board bring-up order |
1588 | 1588 |
1589 With the FT2232x USB subsystem integrated on the Venus board, this subsystem | 1589 The on-board FT2232D subsystem will be the preferred way to interface to the |
1590 will become the only way to access Calypso UARTs for initial bring-up of a | 1590 two Calypso UARTs on FC Venus, and also the preferred way of driving RPWON and |
1591 freshly populated board. Furthermore, our DUART28C-based boot control mechanism | 1591 nTESTRESET boot controls - if everything goes according to plan. However, to |
1592 will be the only way to trigger RPWON and nTESTRESET boot controls - there will | 1592 guard against inoperable boards in the unfortunate event that the built-in USB |
1593 also be a PWON button (see section 3.6), but that one is intended for higher- | 1593 subsystem doesn't work as designed, there will also be a "rescue" 10-pin DUART |
1594 level end user functions after FC handset fw has been loaded and after all other | 1594 header on the board. If all USB subsystem components are populated on the |
1595 bring-up tasks are completed on each board. As a result of these factors, our | 1595 board as we currently intend, the "rescue" DUART header MUST NOT have anything |
1596 FT2232x USB subsystem becomes part of the critical path for board bring-up, and | 1596 connected to it, other than oscilloscope probes - however, if a need arises to |
1597 it will in fact become the very first part to be brought up, before Calypso. | 1597 operate a Venus board via an external DUART28 or other adapter, then some |
1598 components will need to be removed from the USB section of the board to prevent | |
1599 the scenario of two fighting drivers. | |
1600 | |
1601 There will also be a 3-pin boot control header, bringing out RPWON and | |
1602 nTESTRESET, but this provision does not present the same stringent single driver | |
1603 requirements as the "rescue" DUART header, as all drivers for these boot control | |
1604 signals are open drain. | |
1598 | 1605 |
1599 The charging switch will need to be off during board bring-up, and it is | 1606 The charging switch will need to be off during board bring-up, and it is |
1600 expected to remain off during most development activities on FC Venus, to be | 1607 expected to remain off during most development activities on FC Venus, to be |
1601 turned on only rarely when exercising the charging function. | 1608 turned on only rarely when exercising the charging function. |
1602 | 1609 |
1694 There will be no keypad backlight on the Venus board. This secondary backlight | 1701 There will be no keypad backlight on the Venus board. This secondary backlight |
1695 is not needed for firmware development, as it is not managed separately in our | 1702 is not needed for firmware development, as it is not managed separately in our |
1696 fw architecture - instead its control will be absorbed into our R2D BLRR control | 1703 fw architecture - instead its control will be absorbed into our R2D BLRR control |
1697 mechanism on the final handset where this backlight will be added. | 1704 mechanism on the final handset where this backlight will be added. |
1698 | 1705 |
1699 3.6.1. No boot control buttons | 1706 3.6.1. Limited boot control buttons |
1700 | 1707 |
1701 The Mother's original idea for FC Venus was to implement pushbutton switches for | 1708 The Mother's original idea for FC Venus was to implement pushbutton switches for |
1702 all 3 boot controls as in PWON, RPWON and nTESTRESET. However, now that we are | 1709 all 3 boot controls as in PWON, RPWON and nTESTRESET. However, now that we are |
1703 integrating the FT2232x USB subsystem of section 1.12 and the boot control | 1710 integrating the FT2232D USB subsystem of section 1.12 and the boot control |
1704 mechanism of section 1.12.3 as a non-removable part of the Venus board itself, | 1711 mechanism of section 1.12.3 as a non-removable part of the Venus board itself, |
1705 pushbutton switches for RPWON and RESET are being eliminated, leaving only PWON | 1712 the pushbutton switch for RPWON is being eliminated, leaving only PWON in the |
1706 in the "END" position in the main keypad. | 1713 "END" position in the main keypad and a rare-use RESET button. For additional |
1714 context, when I first decided to integrate the FT2232D subsystem with boot | |
1715 control, I was going to drop the RESET button as well - but then I decided that | |
1716 it would be more proper to include at least a footprint for one. My current | |
1717 intent is to populate an actual button for RESET, but to use a different switch | |
1718 part with a shorter actuator and a greater operating force, reducing the | |
1719 probability of accidental resets. | |
1707 | 1720 |
1708 3.7. Audio interfaces | 1721 3.7. Audio interfaces |
1709 | 1722 |
1710 Corresponding to the 3 audio channels of section 1.7, there will be 3 analog | 1723 Corresponding to the 3 audio channels of section 1.7, there will be 3 analog |
1711 audio interfaces on FC Venus: two TRRS jacks and one 2-pin header. These audio | 1724 audio interfaces on FC Venus: two TRRS jacks and one 2-pin header. These audio |