I recently had a similar need for more I/O pins ;-)You can do it, but you must disable the UART the 'hard way'. It is activated by default and overrides the pin-direction (input/output) internally in hardware. Once you've disabled it you cannot use any hardware serial communication anymore (in that program).Insert this at the very beginning of setup()Code: [Select]UCSR0A = 0x00;UCSR0B = 0x00;UCSR0C = 0x03;This sets the uart control & status registers to their default values and turns the uart + port override off.
UCSR0A = 0x00;UCSR0B = 0x00;UCSR0C = 0x03;
That data was taken with the collector wired to Vcc and the emitter to GND + amp-meter in there.Anyhow, it needs 5V to turn on fully. If you only need 40mA per channel that is of less a concern.Maybe this datasheet is a bit clearer on how the values were obtained:http://www.datasheetcatalog.org/datasheet/allegromicrosystems/2801.pdf