Ryan Malloy
48b61f462a
Simulated RX and TX paths via mcltspice, generated 4 SVG waveform plots (2000 data points each), and staged all 8 netlists plus the muki01 schematic as downloadable site assets. Presentation: Starlight Tabs for RX/TX waveform pairs, inline schematic image, dark mode CSS filter for white-background SVGs, and netlist inventory with download links.
83 lines
2.5 KiB
Plaintext
83 lines
2.5 KiB
Plaintext
* BMW I/K-Bus Interface - TX Path VALIDATED (R2=220 fix for 3.3V ESP32)
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* Tests worst realistic scenario: PC817A typical CTR + 1k bus pull-up
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* Also includes RX loopback to verify full signal path
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*
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* Fix: R2 reduced from 470 to 220 ohms
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* Effect: LED current increases from 4.66mA to ~9.3mA
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* Phototransistor base drive doubles: 9.3uA -> 18.6uA
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* Max collector current: 11.2mA -> 22.4mA
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* Supports bus pull-ups down to ~530 ohms
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*
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* PC817 pin order: 1=Anode, 2=Cathode, 3=Collector, 4=Emitter
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* === Power Supplies ===
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V_BAT V12 0 12
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V_MCU VCC 0 3.3
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* === TX Test Signal (byte 0x68 = RAD address) ===
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* Inverted UART: 0V=idle, 3.3V=pulling bus LOW
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* 0x68 = 01101000, LSB first = 00010110
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* 3 ones -> even parity = 1
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* Frame: START(1), 0,0,0,1,0,1,1,0, P(1), STOP(0)
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* (inverted: start=HIGH, data inverted, stop=LOW)
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V_TX TX 0 PWL(
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+ 0u 0
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+ 199.5u 0
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+ 200u 3.3
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+ 512u 3.3
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+ 512.5u 0
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+ 825u 0
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+ 825.5u 3.3
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+ 1137u 3.3
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+ 1137.5u 0
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+ 2000u 0)
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* === Bus Model: 1k pull-up (loaded bus, worst realistic case) ===
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R_PULL V12 IBUS 1k
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C_BUS IBUS 0 100p
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* === TX Driver: Q1 (BC547B) ===
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R5 TX R5_R3 470
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R3 R5_R3 Q1B 10k
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Q1 Q1C Q1B 0 BC547B
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* === TX Optocoupler (U2) ===
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* FIX: R2 changed from 470 to 220 for 3.3V ESP32 compatibility
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R2 VCC U2_A 220
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XU2 U2_A Q1C IBUS 0 PC817 Igain=1m
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* === RX Optocoupler (U1) for Loopback ===
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R1_RX IBUS U1_A 2k
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XU1 U1_A 0 VCC RX PC817 Igain=1m
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R4_RX RX 0 1k
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* === PC817 Subcircuit ===
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.subckt PC817 1 2 3 4
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R1 N003 2 2
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D1 1 N003 LD
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G1 3 N004 N003 2 {Igain}
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C1 1 2 18p
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Q1 3 N004 4 [4] NP
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.model LD D(Is=1e-20 Cjo=18p)
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.model NP NPN(Bf=1200 Vaf=140 Ikf=100m Rc=1 Cjc=19p Cje=7p Cjs=7p C2=3e-15)
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.ends PC817
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* === BC547B Model ===
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.model BC547B NPN(IS=2.39E-14 NF=1.008 ISE=3.545E-15 NE=1.541 BF=294.3 IKF=0.1357 VAF=63.2 NR=1.004 ISC=6.272E-14 NC=1.243 BR=7.946 IKR=0.1144 VAR=25.9 RB=1 IRB=1.00E-06 RBM=1 RE=0.4683 RC=0.85 XTB=0 EG=1.11 XTI=3 CJE=1.358E-11 VJE=0.65 MJE=0.3279 TF=4.391E-10 XTF=120 VTF=2.643 ITF=0.7495 PTF=0 CJC=3.728E-12 VJC=0.3997 MJC=0.2955 XCJC=0.6193 TR=1.00E-32 CJS=0 VJS=0.75 MJS=0.333 FC=0.9579 Vceo=45 Icrating=100m mfg=NXP)
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* === Simulation ===
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.tran 0 2000u 0 0.1u
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* === Measurements ===
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.meas tran IBUS_HIGH MAX V(IBUS)
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.meas tran IBUS_LOW MIN V(IBUS)
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.meas tran IBUS_SWING PP V(IBUS)
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.meas tran U2_LED_CURRENT MAX I(R2)
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.meas tran Q1_VCE_SAT MIN V(Q1C)
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.meas tran RX_LOOPBACK_HIGH MAX V(RX)
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.meas tran RX_LOOPBACK_LOW MIN V(RX)
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.meas tran BUS_RISE TRIG V(IBUS) VAL=1.0 RISE=1 TARG V(IBUS) VAL=7.0 RISE=1
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.meas tran BUS_FALL TRIG V(IBUS) VAL=7.0 FALL=1 TARG V(IBUS) VAL=1.0 FALL=1
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.backanno
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.end
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