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If you are using the GPIO connector to drive LEDs, connect the LED outputs to the LED ANODE and connect the LED CATHODE to the ground. If you want to connect another device, then the output is capable of sourcing or sinking up to 3.3V at 24mA, but there is a series resistor of 100Ω in each line.
The connector also allows the connecting of external contact closures to the ground. In order to connect a switch, connect one side of the switch to the switch input, and connect the other side to one of the ground pins on the GPIO connector. The connector can also supply 3.3V at up to 500mA to an external device. The 3.3V output is polyfuse-protected and can source up to 500mA.
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The GPIO outputs have 100Ω series resistors; the GPIO inputs have 1K pullup resistors to 3.3V; and the input threshold is 2V high and .8V low. The high voltage is not problematic, but the low voltage can be if there are too many inputs connected to one output. |
1 out driving 1 in | V=3.3*100/(100+1,000)=0.3 |
1 out driving 2 in | V=3.3*100/(100+500)=0.55 |
1 out driving 3 in | V=3.3*100/(100+333.3)=0.76 |
1 out driving 4 in | V=3.3*100/(100+250)=.94 (This is too high, so 1 output driving 3 inputs is the maximum) |
The following table describes the pinout of the GPIO on the HO523:
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The full-scale voltage output of the analog audio is 2V RMS. The minimum load impedance is 32Ω.
The analog audio connector has the following pinout:
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A serial cable plug that is inserted into the 3.5mm jack should use the following signaling:
- Tip: Transmit
- Ring: RecieveReceive
- Sleeve: Ground
The following diagram illustrates the behavior of the TX and RX signal:
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