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The UART (asynchronous serial) interface is a 3.5mm (1/8") jack and will interoperate with most RS-232 compatible devicesthat uses TTL for communication. The receiver will tolerate input voltages between -30V and +30V, with anything below 3V interpreted as a logical 1. The transmitter drives +5V for logical 0 and 0V for logical 1.
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The 3.5mm serial port can interoperate with some RS-232 compatible devices. It can receive from any RS-232 device, but transmission may not work depending on the electrical characteristics of the device. |
The default baud rate of the RS-232 interface is 115200, with no parity, 8 data bits, and 1 stop bit. These settings can be configured in the software. The serial interface supports TX, RX, and ground only—RTS/CTS hardware flow control is not supported.
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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 HD223 and HD1023:
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The following schematic illustrates the pinout of the GPIO connector.
RJ45 LAN
The HD223 and HD1023 have an RJ45 connector for 1000BASE-T networking. The maximum length for Cat 5E cable is 100 meters; the allowed length can be higher or lower depending on the quality of the cable.
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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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