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comparison sim-card-detect @ 368:82d5cc869bf1

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sim-card-detect observations note added
author Mychaela Falconia <falcon@freecalypso.org>
date Thu, 26 Nov 2020 04:45:20 +0000
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367:6dd0fc53bcba 368:82d5cc869bf1
1 On the Mother's D-Sample board the SIM card status register (FFFE:0002)
2 reads:
3
4 0x000A (CD bit 0) when the SIM socket is empty
5 0x000B (CD bit 1) when a card is inserted and the switch is shorted
6
7 These register readings match CAL207 register document.
8
9 On FCDEV3B Calypso SIM_CD input is tied high following Leonardo and Openmoko,
10 and the register reads 0x000B - thus we reach the conclusion that CAL000
11 document is correct in that logic high on SIM_CD is supposed to indicate SIM
12 inserted, whereas logic low is supposed to indicate an empty SIM socket.
13
14 However, the netlist extracted from the PADS PCB file for E-Sample (Calypso+
15 chipset) shows the opposite arrangement: it shows a pull-up resistor to V-IO on
16 the SIM-CD net, and the switch in the SIM socket shorts this net to ground.
17 Perhaps the sense of this signal is inverted on Calypso+? We have no way of
18 knowing because we have no documentation for Calypso+, but we do know that its
19 ABB companion Syren reversed the sense of its test reset signal (relative to
20 Iota) for no apparent reason, hence such signal polarity reversals are not out
21 of the question.