48 lines
1.1 KiB
Plaintext
48 lines
1.1 KiB
Plaintext
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= Arduino Programming Techniques =
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This is mostly gonna be C++
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== Accessing a GPIO line ==
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{{{
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//data direction register bit
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unsigned char *portDDRB;
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portDDRB = (unsigned char *) 0x24;
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}}}
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First we get an 8bit pointer and load it with a hard coded value of
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the data-space address for that register
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See [[arduino_nano#Pins]]
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== Bit masks ==
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{{{
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#define BIT6_MASK 0x40 // 0100 0000
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#define BIT5_MASK 0x20 // 0010 0000
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*register_pointer = (*regiser_pointer) & (~BIT6_MASK);
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*register_pointer = (*regiser_pointer) | BIT5_MASK;
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}}}
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For the first one we find the compilemnt then '&' it with the current
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register values, which will only flip the selected bit.
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For the second one we '|' it with the contents, setting a 1 in the 5th position
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== Polling GPIO pins ==
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repeatedly reading the value of the input pins and comparing the current value
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to the previously-read value to determine if an external signal event has
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occurred.
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We can do this by comparing the last known value of the gpio pin with the
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current one
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See [[arduino_nano#Pins]]
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[[embedded]]
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