#00-2, M1S: Three Direct I/O Lines and Ground
Function: Three directly exposed I/O lines of the microcontroller plus the ground line
Form factor: M1S
Category: Blank module
Special needs: ---
Power requirements: 5V/20mA
As with Tibbit #00-1, this device allows you to work with CPU lines directly. The only difference is that one of the lines is replaced by the ground (GND) line.
The GND line may be necessary when using Tibbit #00-2 with Tibbit #21 (four terminal blocks). As #21 doesn't have its own dedicated ground, if the ground is necessary (and it usually is), then it must come from the neighboring "M" device, such as Tibbit #00-2.
Note that a CPU I/O line has a voltage swing from 0-3.3V when the line is enabled (io.enabled = 1 — YES). The voltage may be close to 5V when the line is disabled (io.enabled = 0 — NO). This is because the CPU has weak pull-up resistors connected to 5V.
Three yellow LEDs are connected to three control lines of the CPU (through buffering gates). LEDs light up for the LOW state of control lines.