Connect the GPIO

brightsign players have 12 total connections eight gpio connections for any combination of buttons or leds; two for 3 3v power, and two for ground the gpio port requires a simple contact closure connection for an explanation of the different gpio button pins and grounds, consult the docid\ uyyjyej6qojy1hksbrlpu documentation for your player model each button/led must be connected to a gpio pin and to a ground the switch/led connector allows the player to control external leds or other devices requiring 24ma of current or less you can use a http //www hms electronics com/brightsign/brightsign products htm to connect more than eight buttons/leds, support higher voltage leds, or use other outputs leds to connect to an led, you must connect the led outputs to the led anode and then connect the led cathode to ground if you want to connect another player, 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 to connect an led to the player gpio connector connect the anode of the led to the pwr pin, and cathode to the gnd pin now the led will be on and will stay on use this to verify that the led is working and that there is board power brightsign players support 3 3v leds directly, without external power we recommend using a 10 100 ohm series resistor to protect the led once you wire the anode to the pwr pin for testing, the led anode is wired to a pin like the buttons connect the anode to the switch/led connector pin and leave the cathode connected to the gnd pin you can now control the led with a brightauthor\ connected project, brightauthor project, or script if the led is too dim, remove the series resistor, as the board has an internal 100 ohm series resistor to limit current to the led switches to connect to a switch connect one side of the switch to the switch input connect the other side of the switch to one of the ground pins on the db15 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 if one player is driving the inputs on another player, then you can drive at most three inputs from one output the following calculations explain this limitation gpio calculations png the gpio outputs have 100ω series resistors; the gpio inputs have 1k pull up resistors to 3 3v; and the input threshold on the 541 chips 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 examples note that the first two examples reference older brightsign models that had 15 pin gpio connectors how to wire four buttons and four leds (20 kb) how to wire three buttons and three leds (10 kb) an example of a low voltage button that only requires 3 3v for its led (100kb)