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comparison FCDEV3B-repackaging @ 5:f920c9a68d45

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FCDEV3B-repackaging: clarified the cost increment
author Mychaela Falconia <falcon@freecalypso.org>
date Thu, 11 Oct 2018 04:58:17 +0000
parents 1dbc8c5d9698
children 700d6cff63bb
comparison
equal deleted inserted replaced
4:1dbc8c5d9698 5:f920c9a68d45
112 * Both Calypso UARTs need to be wired in an accessible way so that our standard 112 * Both Calypso UARTs need to be wired in an accessible way so that our standard
113 FC Magnetite firmware can be used with the AT command interface on the MODEM 113 FC Magnetite firmware can be used with the AT command interface on the MODEM
114 UART and RVTMUX on the IrDA UART. 114 UART and RVTMUX on the IrDA UART.
115 115
116 * Our fw configures the MODEM UART with hardware flow control enabled; if your 116 * Our fw configures the MODEM UART with hardware flow control enabled; if your
117 applications lacks RTS/CTS signals, then Calypso's CTS_MODEM signal needs to 117 application lacks RTS/CTS signals, then Calypso's CTS_MODEM signal needs to
118 be pulled down to GND so it is seen as asserted. 118 be pulled down to GND so it is seen as asserted.
119 119
120 * Our fw configures the 4 MCSI/GPIO pins as MCSI rather than GPIO. If your 120 * Our fw configures the 4 MCSI/GPIO pins as MCSI rather than GPIO. If your
121 board does not use MCSI because you are tapping VSP instead or not using any 121 board does not use MCSI because you are tapping VSP instead or not using any
122 digital voice interface at all, then you should put pull-down resistors on 122 digital voice interface at all, then you should put pull-down resistors on
123 MCSI_RXD, MCSI_CLK and MCSI_FSYNCH, otherwise these signals will float. 123 MCSI_RXD, MCSI_CLK and MCSI_FSYNCH, otherwise these signals will float.
124 MCSI_RXD can be directly tied to GND without a resistor as it is always an
125 input to the Calypso, but MCSI_CLK and MCSI_FSYNCH need to be pulled down
126 with resistors: our fw can enable TI's "Bluetooth headset" and "Bluetooth
127 cordless" modes, in which case these signals become outputs. If the signals
128 are switched to being outputs by software command but are tied to GND on the
129 board, the result will be a shorted output driver which could damage the chip,
130 and it is clearly not acceptable to produce hardware that can be damaged by
131 an AT command, even an obscure and non-standard one.
132
133 Cost increment
134 ==============
135
136 If you don't need huge flash and XRAM capacity, don't have a DTR input and are
137 not using MCSI, then the incremental cost of being firmware-compatible with
138 FCDEV3B compared to Openmoko's approach of leaving all unused signals
139 unconnected and using a smaller flash+RAM chip consists of:
140
141 * A logic voltage level translating buffer to provide a reset to the flash chip
142 that meets its timing requirements;
143
144 * 3 pull-down resistors on GPIO3, MCSI_CLK and MCSI_FSYNCH;
145
146 * Direct connections to GND on DSR_MODEM and MCSI_RXD pins.
147
148 For parties other than the Mother, it is up to you to decide if being firmware-
149 compatible is worth the cost increment or not, but all modem repackagings
150 produced by us under the FreeCalypso brand will follow these software and
151 firmware configuration management compatibility guidelines, and the same is
152 required for anyone else who wishes for their hardware variant to be accepted
153 into the FreeCalypso family.
124 154
125 Tapping VSP for the digital voice interface 155 Tapping VSP for the digital voice interface
126 =========================================== 156 ===========================================
127 157
128 The Calypso+Iota chipset includes an interface called VSP for Voice Serial Port; 158 The Calypso+Iota chipset includes an interface called VSP for Voice Serial Port;