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--- xro:beaglebone [2015-12-09 00:21]
xro
+++ xro:beaglebone [2015-12-09 02:11]
xro
@@ Line 49: / Line 49: @@
 ==== Transient State of pins during startup ====
+Basically, until the Device-Tree-Overlays are loaded, the Beageblone-Blacks gpio pins are in ''INPUT'' mode and sometimes, during bootup, may switch devices your relays and other stuff that depends on your pins being configured for ''OUTPUT'' at level 0, when powering up.
+There are two possible solution that I know of.
+  - Don't power up your external gpio-controlled hardware before the BeagleBoneBlack has booted
+  - Guard your GPIO Pins with some Peripheral-Buffer IC's that need an **EN**able signal.
+In both cases, you still need a pin to connect the EN signal or power-relay for our peripherals,
+a PIN that you can trust to pull your pheripheral LOW even during bootup.
+A good choice for that are most pins that, per default, are muxed not to the GPIOchips but to internal devices like UART, SPI, I2C.
+The following is a list of measurement, which pins pull which direction (HIGH/LOW) during bootup.
+^PIN^ Test1 ^ Test2 ^ Test3 ^
+|P8_01 | 0 (DGND) |||
+|P8_02 | 0 (DGND) |||
+|P8_03 | 1 | 1 ||
+|P8_04 | 1 | 1 ||
+|P8_05 | 1 | 1 ||
+|P8_06 | 1 | 1 ||
+|P8_07 | 1 | 1 ||
+|P8_08 | 1 | 1 ||
+|P8_09 | 1 | 1 ||
+|P8_10 | 1 | 1 ||
+|P8_11 | 0 | 0 ||
+|P8_12 | 0 | 0 ||
+|P8_13 | 0 | 0 ||
+|P8_14 | 0 | 0 ||
+|P8_15 | 0 | 0 ||
+|P8_16 | 0 | 0 ||
+|P8_17 | 0 | 0 ||
+|P8_18 | 0 | 0 ||
+|P8_19 | 0 | 0 ||
+|P8_20 | 0 | 1 ||
+|P8_21 | high freq signal, 0 |||
+|P8_22 | float or high-freq, 1 |||
+|P8_23 | 1 | 1 ||
+|P8_24 | 1 | 1 ||
+|P8_25 | PWM signal 1 ||
+|P8_26 | 1 | 1 ||
+|P8_27 | 0 | 0 ||
+|P8_28 | 1 | 0 ||
+|P8_29 | 0 | 0 ||
+|P8_30 | 0 | 0 ||
+|P8_31 | 1 | 1 ||
+|P8_32 | 1 | 0 ||
+|P8_33 | 0 | 0 | 0 |
+|P8_34 | 0 | 0 | 0 |
+|P8_35 | 0 |||
+|P8_36 | 0 |||
+|P8_37 | 0 |||
+|P8_38 | 0 |||
+|P8_39 | 0 |||
+|P8_40 | 0 |||
+|P8_41 | 1 |||
+|P8_42 | 1 |||
+|P8_43 | 1 |||
+|P8_44 | 1 |||
+|P8_45 | 0 |||
+|P8_46 | 0 |||
+|P9_01 | 0 (DGND) |||
+|P9_02 | 0 (DGND) |||
+|P9_03 | 1 (3V3) |||
+|P9_04 | 1 (3V3) |||
+|P9_05 | 1 (VDD 5V) |||
+|P9_06 | 1 (VDD 5V) |||
+|P9_07 | 1 (SYS 5V) |||
+|P9_08 | 1 (SYS 5V) |||
+|P9_09 | PWR_BUT |||
+|P9_10 | 1 (SYS_RESET) |||
+|P9_11 | |||
+|P9_12 | 1 |||
+|P9_13 | 1 |||
+|P9_14 | 0 |||
+|P9_15 | pulsing 1 , every 480µs |||
+|P9_16 | 0 | 0 ||
+|P9_17 | 0 | 0 ||
+|P9_18 | 1 | 0 ||
+|P9_19 | 1 | 1 ||
+|P9_20 | 1 | 1 ||
+|P9_21 | 1 | 1 | 1 |
+|P9_22 | 1 | 1 | 1 |
+|P9_23 | 0 | 0 ||
+|P9_24 | 1 | 1 ||
+|P9_25 | 0 | 0 ||
+|P9_26 | 1 | 1 ||
+|P9_27 | 0 | 0 ||
+|P9_28 | 0 | 0 ||
+|P9_29 | 0 | 0 ||
+|P9_30 | 0 | 0 ||
+|P9_31 | 0 |||
+|P9_32 | 1 (VDD_ADC) |||
+|P9_33 | AIN4 |||
+|P9_34 | 0 (GND_ADC) |||
+|P9_35 | AIN6 |||
+|P9_36 | AIN5 |||
+|P9_37 | AIN2 |||
+|P9_38 | AIN3 |||
+|P9_39 | AIN0 |||
+|P9_40 | AIN1 |||
+|P9_41 | 0 | 0 ||
+|P9_42 | 0 | 0 ||
+|P9_43 | DGND |||
+|P9_44 | DGND |||
+|P9_45 | DGND |||
+|P9_46 | DGND |||

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