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FCDEV3B-repackaging: updates for working MCSI and flash autodetect
author Mychaela Falconia <falcon@freecalypso.org>
date Thu, 28 Mar 2019 08:56:27 +0000
parents 700d6cff63bb
children
comparison
equal deleted inserted replaced
10:17003ecbb9fc 11:f57f29dcc6d6
1 Repackaging FreeCalypso modem into different physical form factors 1 Repackaging FreeCalypso modem into different physical form factors
2 ================================================================== 2 ==================================================================
3
4 [This document was originally written in 2018-10; subsequent updates
5 are noted inline in the same bracketed form as this note.]
3 6
4 As of this writing, our FreeCalypso Triband Modem Solution has reached the 7 As of this writing, our FreeCalypso Triband Modem Solution has reached the
5 status of a finished product: it is no longer experimental or developmental, 8 status of a finished product: it is no longer experimental or developmental,
6 it is now fully fit for operational use on live public GSM networks in end user 9 it is now fully fit for operational use on live public GSM networks in end user
7 applications that need a standards-compliant GSM+GPRS modem. However, at the 10 applications that need a standards-compliant GSM+GPRS modem. However, at the
62 will be broken. We realize that this flash and RAM capacity (16 MiB and 65 will be broken. We realize that this flash and RAM capacity (16 MiB and
63 8 MiB, respectively) is extreme overkill for typical modem applications 66 8 MiB, respectively) is extreme overkill for typical modem applications
64 outside of development, but supporting multiple flash chip types would 67 outside of development, but supporting multiple flash chip types would
65 introduce a configuration management burden which we are not willing to 68 introduce a configuration management burden which we are not willing to
66 take on. 69 take on.
70
71 [2019-03 update: we now have working flash chip type autodetection, and
72 commercial modem products can use a smaller flash+RAM chip, specifically
73 Samsung K5A3240CTM or K5A3281CTM as used by Openmoko.]
67 74
68 * Calypso's unused DSR_MODEM/LPG pin was left unconnected in Openmoko's version 75 * Calypso's unused DSR_MODEM/LPG pin was left unconnected in Openmoko's version
69 but on our FCDEV3B it is tied to GND on the board. Other boards seeking to 76 but on our FCDEV3B it is tied to GND on the board. Other boards seeking to
70 be FreeCalypso-compatible need to have this pin tied to GND as well because 77 be FreeCalypso-compatible need to have this pin tied to GND as well because
71 our firmware leaves this pin in its default power-up config of DSR_MODEM input 78 our firmware leaves this pin in its default power-up config of DSR_MODEM input
138 FCDEV3B compared to Openmoko's approach of leaving all unused signals 145 FCDEV3B compared to Openmoko's approach of leaving all unused signals
139 unconnected and using a smaller flash+RAM chip consists of: 146 unconnected and using a smaller flash+RAM chip consists of:
140 147
141 * A logic voltage level translating buffer to provide a reset to the flash chip 148 * A logic voltage level translating buffer to provide a reset to the flash chip
142 that meets its timing requirements; 149 that meets its timing requirements;
150
151 [2019-03 update: the above is no longer required, you can now use one of the
152 smaller flash chips which are compatible with TI's silly FDP scheme and thus
153 don't need the extra translating buffer IC for reset.]
143 154
144 * 3 pull-down resistors on GPIO3, MCSI_CLK and MCSI_FSYNCH; 155 * 3 pull-down resistors on GPIO3, MCSI_CLK and MCSI_FSYNCH;
145 156
146 * Direct connections to GND on DSR_MODEM and MCSI_RXD pins. 157 * Direct connections to GND on DSR_MODEM and MCSI_RXD pins.
147 158
166 cannot count on, we won't be able to use MCSI reliably until and unless we 177 cannot count on, we won't be able to use MCSI reliably until and unless we
167 undertake to fully reverse their DSP ROM code from disassembly, which would be 178 undertake to fully reverse their DSP ROM code from disassembly, which would be
168 an extremely major and very costly undertaking. Because of this unfortunate 179 an extremely major and very costly undertaking. Because of this unfortunate
169 situation, the alternative way of tapping into VSP needs to be given 180 situation, the alternative way of tapping into VSP needs to be given
170 consideration. 181 consideration.
182
183 [2019-03 update: we got MCSI working now, please read the Calypso-digital-voice
184 article for more info about both MCSI and VSP options.]
171 185
172 Tapping into VSP is absolutely not possible on our current FCDEV3B, as the 186 Tapping into VSP is absolutely not possible on our current FCDEV3B, as the
173 signals in question are currently routed directly from one BGA to another and 187 signals in question are currently routed directly from one BGA to another and
174 do not come up to the surface at any accessible point. The same situation holds 188 do not come up to the surface at any accessible point. The same situation holds
175 on every other existing Calypso phone and modem known to us - after all, VSP was 189 on every other existing Calypso phone and modem known to us - after all, VSP was