Borg Shift Register PCB V1.2

This shift register PCB can be assembled in two ways, either with a 74165 to get 8 inputs or with a 74595 to get 8 outputs. It can be connected to an SPI bus using additional lines for loading and storing the data. Multiple boards can be cascaded. The limit is only the driving capability of the clock, load and store output.

Schema, production files in the format needed for Seeed Studio.

Usage

The boards can be connected to a chain, input and output boards can be mixed. Connect the controller to P1 of the first board. Then Connect P2 to P1 of the next board using a 1:1 cable, and so on. On the last board set the jumper J1 to feed back the data from the last PCB to the controller. The inputs/outputs are on P3 and P4.

All data is always shifted through all registers no matter if they are inputs or outputs. So if the chain consists of an input shift register followed by an output shift register alwyas 16 bits have to be shifted through. The first bit sent ends up in output 8, the 8th bit in output 1, the following 8 bit will be stored in the input register and have no effect. The first 8 bit read from the register come from the output register and can be ignored. The next 8 bit contain the inputs, input 8 first and input 1 last.

Initializing

Configure /MR, SHCP, DOUT, /PL and STCP as output, DIN as input.
Set /MR and STCP low, set SHCP and /PL to high.
Set /MR high.
Set STCP high.

Shifting

Set /PL low, then high again to load the inputs.
Set DOUT to the value of the next bit to be sent.
Set SHCP low.
Read DIN.
Set SHCP high again to shift the registers.
Repeat from step 2 until all bits have been shifted.
Set STCP low, then high again to store the outputs.

Using SPI

To use the shift register PCB with SPI make the following connections:

Controller	Shift Register PCB
GND	GND
VCC	VCC
GPIO 1	/MR
SCK	SHCP
MOSI	DIN
MISO	DOUT
GPIO 2	/PL
GPIO 3	STCP
-	NC1
-	NC2

Connectors

P1: Control Input

1	GND	Power ground.
2	VCC	Power supply. HC: 2.0V - 5.5V. HCT: 4.5V - 5.5V.
3	/MR	Master reset of 74595, low active.
4	SHCP	Shift the register on the rising edge.
5	DIN	Serial data input to the shift register.
6	DOUT	Serial data out.
7	/PL	Load inputs into shift register, low active.
8	STCP	Store shift register in output registers on the rising edge.
9	NC1	Not connected, just fed through to P2 and P4.
10	NC2	Not connected, just fed through to P2 and P4.

P2: Control Output

1	GND	Power ground.
2	VCC	Power supply output.
3	/MR	Fed through from P1.
4	SHCP	Fed through from P1.
5	DOUT	Serial data out from the shift register.
6	DIN	Fed through to DOUT on P1.
7	/PL	Fed through from P1.
8	STCP	Fed through from P1.
9	NC1	Fed through from P1.
10	NC2	Fed through from P1.

P3: Input/Output

1	GND	Power ground.
2	VCC	Power supply output.
3	1	Input/output 1.
4	2	Input/output 2.
5	3	Input/output 3.
6	4	Input/output 4.
7	5	Input/output 5.
8	6	Input/output 6.
9	7	Input/output 7.
10	8	Input/output 8.

P4: Power

Some extra power pins and the "not connected" pins for free use.

1	GND	Power ground.
2	GND	Power ground.
3	VCC	Power supply output.
4	VCC	Power supply output.
5	NC1	Not connected 1.
6	NC1	Not connected 1.
7	NC2	Not connected 2.
8	NC2	Not connected 2.

J1: Data Feedback

Jumper J1 connects DOUT on P2 with DIN on P2. It has to be set on the last board in the chain to feed back the serial data to the controller. On all other boards it must not be set. In Position 1-2 it feeds back the output voltage of Q7 directly. In Position 2-3 it feeds back the output voltage of Q7 reduced by the level translator D1/D2/R1.

Assembly

D1, D2, and R1 are optional, they are only needed if a level translator for the DOUT feedback pin is needed, and only on the last PCB in the chain.

Bill of Materials for Outputs

Ref.	Count	Description
-	1	Borg Shift register PCB
U1	1	74HC595
U2, U3	0	not used
P1, P2, P3	3	10 pin IDC connectors.
P4	1	10 pin screw terminal, 5mm spacing.
J1	1	Jumper
C1	1	100nF block capacitor.
D1	1	3.3V Z-diode (optional)
D2	1	BAT43 or 1N4148 (optional)
R1	1	1k resistor (optional)

Bill of Materials for Inputs

Ref.	Count	Description
-	1	Borg Shift register PCB
U1	0	not used
U2	1	74HC165
U3	1	10k resistor network, 8 resistors with common pin.
P1, P2, P3	3	10 pin IDC connectors.
P4	1	10 pin screw terminal, 5mm spacing.
J1	1	Jumper
C1	1	100nF block capacitor.
D1	1	3.3V Z-diode (optional)
D2	1	BAT43 or 1N4148 (optional)
R1	1	1k resistor (optional)

Note: Standard configuration of U3 is as pull up resistors. It can be mounted as pull down, then the common pin goes into the GND pad next to U3.

Revisions

V1.2: Added level translator for DOUT, removed the screw terminal
V1.1: Added pullups or pulldown.
V1.0: First version. There are no pullup (or pulldown) resistors for the inputs. They have to be added externally or can be soldered to U1 which is unused for input boards.