view venus/src/core/int_vcxo_passive.v @ 70:8bc2aa52fd23

manual RESET button new part: 260 g force, shorter actuator One of the main envisioned use cases for FC Venus is field demonstration: the board will be carried around, mounted on a sheet of acrylic or somesuch, it will have a battery and an antenna connected, there will be a test SIM with active service inserted, and the setup will be ready to demonstrate as a working phone at a moment's notice. But when a demo is not actively in progress, the fully assembled setup will be transported around in a big and loose ESD bag, and it will need to be equivalent to a traditional phone in its switched-off state: battery present, RTC keeping time, but not switched on all the time. Having a RESET button of the same keyswitch type as used for the regular keypad and PWON would cause a problem for such field transport scenarios: any spurious press of this button would cause a "misc boot" switch-on. Short spurious presses of PWON are filtered out by the firmware (automatic power-off if the button isn't held down long enough), but the same cannot be done for super-low-level nTESTRESET. However, a button with significantly greater operating force and a shorter actuator (not sticking out to the same height as the regular keypad buttons) should be much safer.
author Mychaela Falconia <falcon@freecalypso.org>
date Thu, 02 Dec 2021 22:40:39 +0000
parents d0b6c4915397
children
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/*
 * This module captures the mysterious all-passive circuit between Iota's
 * AFC output and Rita's XIN input as depicted on the Leonardo schematics.
 * This circuit defies understanding, but it appears in Openmoko's GSM
 * modem (unchanged from Leonardo) and that modem works, hence we deem
 * this voodoo circuit to be suitable for mindless copying w/o understanding...
 *
 * Note that C205 is not included here, as it's already been included
 * in the abb_block wrapper instead.
 */

module int_vcxo_passive (AFC_in, XIN_connection, GND);

input AFC_in, GND;
inout XIN_connection;

wire R217_to_xtal, xtal_to_R211, R211_to_C225;

resistor R217 (AFC_in, R217_to_xtal);
varactor_diode D200 (.C(R217_to_xtal), .A(GND));
capacitor C226 (R217_to_xtal, GND);
xtal_4pin_pkg xtal (.pin_1(xtal_to_R211), .pin_2(GND),
		    .pin_3(R217_to_xtal), .pin_4(GND));
resistor R211 (xtal_to_R211, R211_to_C225);
capacitor C224 (R211_to_C225, GND);
capacitor C225 (R211_to_C225, XIN_connection);

endmodule