Click Shield

The Red Pitaya Click Shield extension module enables users to extend Red Pitaya hardware with two MIKROE Click Board™ and power them and the Red Pitaya from either an external USB C power adapter or a 12-24 Volt external power supply. Using U.FL patch cables, the shield can also be utilised for high-performance clock and trigger synchronisation between multiple Red Pitaya units and/or other devices. An external reference clock can also be connected to the shield through the U.FL connector.

Highlights:

• Two mikroBUS™ sockets, allowing interface with more than 1500 MIKROE Click Board™ devices.

• High-performance clock and trigger synchronisation between multiple Red Pitaya units or other devices.

• Powering Red Pitaya through an external power supply (12-24 V or via USB-C connector).

What is in the box?

• 1x Red Pitaya Click Shield.

• 3x U.FL to U.FL patch cable for trigger and clock synchronisation.

Compatibility

Note

Depending on which Red Pitaya board model you are using, some features of the Red Pitaya Click Shield might not be applicable.

The clock synchronisation is compatible only with the following board models:

• STEMlab 125-14 PRO Gen 2.

• STEMlab 125-14 PRO Z7020 Gen 2.

• STEMlab 125-14 External Clock [1].

• SDRlab 122-16 External Clock.

• STEMlab 125-14 4-Input.

Switching between the External and Internal clock is available only on the STEMlab 125-14 4-Input (CLK SEL pin) but will be compatible with all future Red Pitaya board redesigns.

Trigger synchronisation and MIKROE Click Board™ are compatible with all board models.

Here is a compatibility table:

Click Shield Feature Compatibility Gen 2
	STEMlab 125-14 Gen 2	STEMlab 125-14 Pro Gen 2 STEMlab 125-14 Pro Z7020 Gen 2
Click Boards (microBus)	Yes	Yes
High speed Clock Synchronisation	No	Yes
Powering options	Yes	Yes
Clk Switch (Internal/External)	No	Yes

Click Shield Feature Compatibility Original Gen
	STEMlab 125-14 STEMlab 125-14 LN STEMlab 125-14-Z7020-LN	SDRlab 122-16	STEMlab 125-14 ext. clk SDRlab 122-16 ext. clk	STEMlab 125-14 4-Input	SIGNALlab 250-12
Click Boards (microBus)	Yes	Yes	Yes	Yes	Yes
High speed Clock Synchronisation	No	No	Yes	Yes	No
Powering options	Yes	Yes	Yes	Yes	No
Clk Switch (Internal/External)	No	No	No	Yes	No

What are Click Boards?

MIKROE Click Board™ by MirkoElektronika are small add-on boards designed to simplify the process of developing electronic projects by providing a pre-built and tested module with specific functionality. Currently, over 1500 click boards are available in different categories, including communication, display, sensors, storage, motor control, mixed signals, and others.

These Click Boards are an innovative and efficient way to develop hardware projects, whether for beginners or experienced developers. MikroElektronika Click Boards are very easy to use. They come with a standard mikroBUS™ socket connector that can be easily plugged into the Red Pitaya Click Shield.

Technical specifications

Connectors

Warning

The E1 and E2 extension connectors on Red Pitaya boards are wider than the Click Shield’s mating connector, which physically allows the shield to be seated in up to three different positions. Only the centre position is correct, where all pins are aligned. Connecting the shield in the wrong position will result in incorrect pin mapping and may damage the board or the shield. Always double-check the alignment before powering on.

Click Shield Label	Red Pitaya Pin	Notes
CLK IN+	ADC CLK+	One-cable clock
CLK IN-	ADC CLK-
CLK OUT+	ADC CLK+	One-cable clock
CLK OUT-	ADC CLK-
REF CLK IN	DIO10_P	Reference clock Input
TRIG IN	DIO0_P	External trigger Input
TRIG OUT	DIO0_N	External trigger Output

Note

REF CLK IN connector is connected to the DIO10_P GPIO pin, which can act as a reference clock input, but the functionatlity is not included in the base FPGA image, so it must be added by the user.

Switches

Click Shield Label	Red Pitaya Pin	Notes
Clock Select	ADC CLK Select	* EXT (LOW): external clock via CLK IN± pins. * INT (HIGH): Red Pitaya’s own internal oscillator.
CLK OSC	NA	Turn the 125 MHz Oscillator on the Click Shield ON/OFF
VCC Select (2x)	NA	Select the digital logic levels for mikroBUS™ 3V3/5V

Note

INT on the Clock Select switch uses the Red Pitaya’s own oscillator, not the Click Shield’s 125 MHz oscillator — that is a separate circuit controlled by the CLK OSC switch, used to distribute a common clock via CLK OUT±. To use the Click Shield oscillator as the ADC sampling clock, set Clock Select to EXT and enable the CLK OSC switch.

Click board logic: If a specific Click Board requires 5V logic levels, please switch the VCC Select switch to the 5V position.

Jumpers

Click Shield Label	Notes
J1	Connect CLK IN- to Virtual GND (one-cable clock only)
J4	Connect Oscillator CLK- to CLK IN-
J5	Connect Oscillator CLK+ to CLK IN+
J6	Connect DIO0_N (EXT TRIG OUT) pin to TRIG IN
J7	Trigger sync.: Connect DIO0_P (EXT TRIG IN) pin to TRIG OUT
VIN SEL	Select the external power between VEXT and VUSB

Power supply

The Click Shields provide two alternative ways to power the Red Pitaya:

• USB-C external power supply.

• 12-24 V External Power Supply (2-pin screw Terminal Block).

Note

Set the VIN SEL jumper into the correct position depending on whether the USB-C or External Power supply (Terminal Block) is used.

The external power supply powers both the Red Pitaya and the Red Pitaya Click Shield. The maximum power consumption of Red Pitaya is 10 W (5 V, 2 A). The power consumption of the Click Shield greatly depends on the type of Click Boards attached to it (we recommend leaving 5 W just in case). Minimal requirements for the external power supplies:

• USB-C - 5 V, 3 A (15 W).

• External Power Supply - 12-24 V, 1.5 A (15 W).

The voltages must be in the specified range.

If the power is supplied through the Red Pitaya Click Shield, the microUSB power connector on the Red Pitaya board can be disconnected. In short, you do not have to rely on the original Red Pitaya power supply but can use a better power supply if available.

Power options

1. USB-C or External power supply

   

   When the USB type C connector or the External Power Supply is connected to the Click Shield, the PWR diode will glow Blue, and in this setup, the connected Red Pitaya baseboard and all mikroBUS™ sockets will be powered from it.

   
   

2. Standard power supply

   

   When the USB is connected to the Red Pitaya board, the PWR diode will glow Green, and in this setup, the Red Pitaya baseboard itself will be supplied, and it will provide power to the Click Shield, including all mikroBUS™ sockets.

   
   

3. Standard and external power supply

   

   When the USB type C connector is connected to the Click Shield, and the other USB is connected to the Red Pitaya board, the PWR diode will glow Cyan, and in this setup, the mikroBUS™ sockets are powered from the Click Shield side.

Pinout

Here you will find the interconnections between Click Boards (mikroBUS™ pinout) and Red Pitaya pins.

Short pin descriptions:

• Digital pins: PWM, RST, INT

• Analog pins: AN

• UART pins: RX, TX

• SPI pins: CS, SCK, MISO, MOSI

• I2C pins: SCL, SDA

Note

Red Pitaya only has one set of UART and SPI pins, to achieve the functionality of two click boards, some of the digital pins are used for switching SPI and UART between the two click boards:

• DIO1_N == Chip Select 1 (Click board 1).

• DIO3_N == Chip Select 2 (Click board 2).

• DIO5_N == Switching between UART0 (Click board 1)/UART1 (Click board 2).

Click Board 1

Closer to +CLK OUT- pins.

Notes	mikroBUS Pin		Red Pitaya Pin	Red Pitaya Pin	mikroBUS Pin		Notes
Analog input	1	AN	AIN0	DIO1_P	PWM	16	PWM
Reset	2	RST	DIO2_N	DIO2_P	INT	15	Interrupt
SPI Chip select 1	3	CS	DIO1_N	RX	RX	14	UART0 RX
SPI Serial clock	4	SCK	SCK	TX	TX	13	UART0 TX
SPI MISO (SDO)	5	MISO	MISO	SCL	SCL	12	I2C Clock
SPI MOSI (SDI)	6	MOSI	MOSI	SDA	SDA	11	I2C Data
Power supply	7	3V3	3V3	5V	5V	10	Power supply
Ground	8	GND	GND	GND	GND	9	Ground

Click Board 2

Closer to +CLK IN- pins.

Notes	mikroBUS Pin		Red Pitaya Pin	Red Pitaya Pin	mikroBUS Pin		Notes
Analog input	1	AN	AIN1	DIO3_P	PWM	16	PWM
Reset	2	RST	DIO4_N	DIO4_P	INT	15	Interrupt
SPI Chip select 2	3	CS	DIO3_N	RX	RX	14	UART1 RX
SPI Serial clock	4	SCK	SCK	TX	TX	13	UART1 TX
SPI MISO (SDO)	5	MISO	MISO	SCL	SCL	12	I2C Clock
SPI MOSI (SDI)	6	MOSI	MOSI	SDA	SDA	11	I2C Data
Power supply	7	3V3	3V3	5V	5V	10	Power supply
Ground	8	GND	GND	GND	GND	9	Ground

Logic Analyzer Connector

Pin 1 is marked with a small white dot. On the bottom-left side of the connector when the shield is oriented according to the LOGIC ANALYZER text.

Notes	LA Connector Pin	Red Pitaya Pin	Red Pitaya Pin	LA Connector Pin	Notes
Not Connected	1	NC	NC	2	Not Connected
Not Connected	3	NC	NC	4	Not Connected
DIN7	5	DIO7_P	DIO3_P	6	DIN3
DIN6	7	DIO6_P	DIO2_P	8	DIN2
DIN5	9	DIO5_P	DIO1_P	10	DIN1
DIN4	11	DIO4_P	DIO0_P	12	DIN0
Not Connected	13	NC	NC	14	Not Connected
Ground	15	GND	GND	16	Ground

Other

Red Pitaya only has one set of UART pins, to achieve the functionality of two click boards, the following pins are used for switching UART between the two click boards:

Red Pitaya Pin	Notes
DIO5_N	Switching UART0/UART1 (output set to LOW/HIGH)
DIO6_N	Switching UART2/UART3 (Possible future expansion)

Components

• ZL40213 LVDS clock fanout buffer.

• TXS0108 level-shifting voltage translators.

Schematics

• Schematics_Click_Shields_v103.pdf

Note

E1 and E2 connector labels are mixed up in the schematics.

Mechanical Specifications and 3D Models

• 3D_Click_Shield.zip

External clock specifications

According to the datasheet the ZL40213 fanout buffer supports a wide range of differential or single-ended input clock signals:

• LVPECL

• LVDS

• CML

• HSTL

• LVCMOS

For more information on the external clock signal, please check the ZL40213 datasheet. The inputs are in the AC coupling configuration. The chip is powered by a 3V3 power supply.

Examples of use

Synchronisation options

For detailed guide on synchronisation options and Click Shield connection diagram, please refer to the multiboard synchronisation section.

Synchronisation example

Here are examples for synchronising two external clock Red Pitaya units with Click Shields through SCPI commands.

• Multiboard synchronisation examples.

Click Boards

Here are some examples of how to use click boards together with Click Shield and Red Pitaya.

• Click Board Examples
  • Basic Boards
  • Sensors
  • Motors
  • Data Acquisition Boards

Footnotes

[1]

This also includes other variations of STEMlab 125-14 external clock boards, such as STEMlab 125-14 Z7020 external clock, STEMlab 125-14 LN external clock, etc.