#00-1, M1S: Four Direct I/O Lines
Function: Four directly exposed I/O lines of the microcontroller
Form factor: M1S
Category: Blank module
Special needs: ---
Power requirements: 5V/20mA
Sometimes you just want to work with CPU I/O lines directly — no logic or circuitry in between. This Tibbit is (basically) four wires that connect its control lines to I/O lines. Complement it with terminal block Tibbit #20 (nine terminal blocks) or #21 (four terminal blocks), and you have four CPU lines "exposed" and ready to be used.
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.
Combining Tibbit #00-1 with #21 is potentially limited in use, because #00-1 doesn't have dedicated ground or power lines, and Tibbit #21 doesn't have them either. Need ground (and power)? Consider replacing #21 with #20 (it has ground and power), or use Tibbit #00-2 (it provides ground) or #00-3 (it provides ground and power).
Four yellow LEDs are connected to four control lines of the CPU (through buffering gates). LEDs light up for the LOW state of control lines.