doc: update for v1
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README.md
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README.md
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@ -1,14 +1,14 @@
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the USB bug detector identifies USB type-A cables (or devices) with integrated circuits.
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<img src="picture/v0_front.webp" title="front" height="250"/>
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<img src="picture/v0_back.webp" title="back" height="250"/>
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<img src="picture/v1_front.webp" title="front" height="250"/>
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<img src="picture/v1_back.webp" title="back" height="250"/>
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usage
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=====
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to use the USB bug detector, follow the steps provided on the back of the board:
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- insert a CR2025 or CR2032 coin cell battery in the USB bug detector for it to be operational
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- insert a CR1220 coin cell battery in the USB bug detector for it to be operational
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- press on the RESET button to arm the test
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- the BUGGED LED should be off
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- plug the USB cable in the USB receptacle
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@ -17,32 +17,15 @@ to use the USB bug detector, follow the steps provided on the back of the board:
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after the test, to save power, press again on the RESET button.
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to ensure that the USB bug detector works, after pressing on the RESET button, press on the TEST button.
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to ensure that the USB bug detector works, after pressing on the RESET button, press on the SIMULATE button.
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this will simulate a USB plug with integrated circuit.
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the BUGGED LED should switch on.
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this also ensures the battery is not empty.
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when the LED is on, the USB bug detector draws 3 mA.
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when the LED is off, the USB bug detector draws 64 nA.
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this results in a idle battery life of 419 years (for a typical 235 mAh CR2032 battery).
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this is more than the self life of the battery (~ 1%/year).
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fabrication
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===========
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the board has an optional READY LED (with accompanying resistor located next to it).
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only populate it to debug the board.
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the READY LED will we on when the BUGGED LED isn't.
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this allows to always check if the battery is empty, but this also drains the battery even when not testing because an LED is always on.
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the first prototype of the board (v0) offers three populating options, depending on the available NOR gate part and package:
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- 1x SOIC-14 package: U1+C1
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- 2x SOT23-5 pachgae: U2+C2, U3+C3
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- 2x SOT-353 package: U3+C3, U5+C5
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only populate one of the options, depending on the availability of the NOR gate part.
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note: the Cx decoupling capacitor is not really necessary and is just present for good design.
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this results in a idle battery life of 62 years (for a typical 35 mAh CR1220 battery).
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this is on par with the self life of the battery (~ 1%/year).
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mode of operation
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=================
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@ -61,7 +44,7 @@ this minimum 1.6 mA current draw is often caused by the decoupling/bypass capaci
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when charging, the capacitor acts as a short for a small time, allowing current to flow.
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on USB plugs with just resistors, or LEDs, the resulting current flow is not large enough.
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the TEST circuit simulates an integrated circuit by putting a 100 nF capacitor across the USB receptacle.
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the SIMULATE circuit simulates an integrated circuit by putting a 100 nF capacitor across the USB receptacle.
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because of the 1 kOhm inline resistor, and limited 3.3 V provided by the battery, a maximum of 3.3 mA can be drawn by the USB plug.
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this is often not enough to power up integrated circuit properly, particularly if they use a radio interface.
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