Electronic Components that can be used as HCSCI hardware are cheap and easy available. Note: all links on this page are given as examples for information about components, some of the links can be non-relevant at the moment you visit the corresponding pages. Do not consider them as only places where you can buy these components!
These CD74HC4067 modules (16-channel multiplexers) are used for all input/output extensions in HCSCI. CD74HC4067 can be found online for less than $1 for one board, here are some links as examples for reference:- CD74HC4067 Ebay Search results
CD74HC4067 module is a ready-to-use small breakout board that includes the multiplexer IC and input/output pads/pins.
This is a very useful "adapter" board for small SMD integrated circuits (having a surface-mount package). These cheap boards (about $ 0.1 for piece) will help you work comfortably with SMD chips, without the need to make or order PCBs for each device. You need to have basic soldering skills to install the chip on the adapter board.
You can use the SOP28 board for VID6606 (AX1201728SG) quad driver chip, that allows you to make a breackout board for 4x X27.168 stepper motors, as described on this page.
It can be used for any SMD chips that may have 8...28 leads, for example, if you have 16-channel SM16126D LED driver in SMD casing (see links below). Unused pads on the board can serve for additional components - resistors, capacitors, etc.
This DM13A LED driver is used in HCSCI Interface to provide multiple digital outputs (16 LEDs, relay, etc. for one driver). This IC is a register with a latch for 16 constant current LED outputs. Other similar drivers can be used too.
All driver ICs listed below are similar in functionality and pin mapping, so you can use any of them that are easier to get for you.
Some of these ICs have DIP casing (DM13A, DM134, ST2221C), others may have SOP24 casing. But this is not a problem, using them is not so difficult with the SOP28 adapter listed above.
Instead of LED driver you can use 74HC595 register ICs or pre-made breakout boards with them. Unlike the DM13A driver, you need to solder resistors in series with LEDs to the board outputs. Also, these boards can be used for creating 7-segment displays.
This controller board is used with HCSCI to control 24 separate channels of 12-bit PWM output. Designed for LED control, but you can use it for any other PWM-controlled devices - Moving-coil meters, DC motors (speed control), instruments lighting. Price - from $4 for one board (or up to $15 in brand stores).
These controllers are specifically designed for low-power automotive gauge stepper motors and cost about $1 ... $2 for chip.
VID6606, STI6606Z, AX1201728SG chips are the same and can drive 4 motors. 2STI6608 controller has 2 drivers and controls two stepper motors...
The A3967SLB is a microstepping motor driver designed to operate bipolar stepper motors with output drive capability of 30 V and up to 750 mA current. Cost about $1.5 - $2.- "EasyDriver" A3967SLB controller board - AliExpress
This board can drive only one stepper motor, which can be powerful enough (up to 750 mA winding current), also it can be used (if you need it) for X27.x motors in quarter-step mode.