VidorBreakout - Using the pins on the Mini PCIe connector of the Arduino MKR Vidor 4000

15 Mar 2020

The Arduino MKR Vidor 4000 is a powerful but also mysterious board. The FPGA gives it a performance boost over other Arduinos but its functions are very badly documented. There are also very few code examples available on the internet.

Mini PCIe connector of the Vidor

I took a closer look at the Mini PCIe connector and wanted to see which functions are available at these pins.

This connector has 52 positions and the pinout can be grabbed from the official schematics of the board:

Pin	Usage on Vidor	Usage on Mini PCIe card	Usage on Mini PCIe card	Usage on Vidor	Pin
1	WM_PIO2/PEX_PIN1	WAKE#	+3V3AUX	+3V3	2
3	WM_PIO3/PEX_PIN3	COEX1	GND	GND	4
5	WM_PIO4/PEX_PIN5	COEX2	+1.5V	PEX_PIN6	6
7	WM_PIO34/PEX_PIN7	CLKREQ#	UIM_PWR	PEX_PIN8	8
9	GND	GND	UIM_DATA	PEX_PIN10	10
11	PEX_PIN11	REFCLK-	UIM_CLK	PEX_PIN12	12
13	PEX_PIN13	REFCLK+	UIM_RESET	PEX_PIN14	14
15	GND	GND	UIM_VPP	PEX_PIN16	16
17	WM_PIO24	RESERVED	GND	GND	18
19	WM_PIO25	RESERVED	W_DISABLE#	PEX_PIN20	20
21	GND	GND	PERST#	PEX_RST	22
23	PEX_PIN23	PERn0	+3.3VAUX	+3V3	24
25	PEX_PIN25	PERp0	GND	GND	26
27	GND	GND	+1.5V	PEX_PIN28	28
29	GND	GND	SMB_CLK	PEX_PIN30	30
31	PEX_PIN31	PETn0	SMB_DATA	PEX_PIN32	32
33	PEX_PIN33	PETp0	GND	GND	34
35	GND	GND	USB_D-	USB_DM	36
37	GND	GND	USB_D+	USB_DP	38
39	+3V3	+3.3VAUX	GND	GND	40
41	+3V3	+3.3VAUX	LED_WWAN#	PEX_PIN42	42
43	GND	GND	LED_WLAN#	PEX_PIN44	44
45	PEX_PIN45	RESERVED	LED_WPAN#	PEX_PIN46	46
47	PEX_PIN47	RESERVED	+1.5V	PEX_PIN48	48
49	PEX_PIN49	RESERVED	GND	GND	50
51	PEX_PIN51	RESERVED	+3.3VAUX	+3V3	52

So the Vidor is somehow compatible to any standard Mini PCIe header used in computers. At least the GND and 3.3V pins are at the same location as well as the USB pins. On the Vidor the USB pins on the Mini PCIe connector are directly connected to the Micro USB connector on the other end of the board. So when plugged into a Mini PCIe socket on a computer it might be possible to programm the Vidor without using an additional USB cable.

After reset and when nothing is programmed all these pins are inputs. So nothing bad should happen if you plug it into your computer. But care must be taken when you programm the pins. Putting a high level (3.3V) on some of the 1.5V pins might carry some risk of damage.

Using the pins as GPIOs is quite simple. Actually it is already shown in the VidorTestSketch ( https://github.com/vidor-libraries/VidorPeripherals/blob/master/examples/VidorTestSketch/VidorTestSketch.ino ):

  // Ok, so we know now that the FPGA contains the extended GPIO IP
  // Please refer to the online documentation for the actual pin assignment
  // Let's configure pin A0 to be an output, controlled by the FPGA
  FPGA.pinMode(33, OUTPUT);
  FPGA.digitalWrite(33, HIGH);

The difficult part is to figure out why they use 33 as pin number. It is somehow common knowledge that MKR pins (AREF,A0..A6, D0..D14) have the numbers 32 to 54 assigned. So A0 is 33, A1 is 34 and so on. D14 is 54.

But what about the pins on the Mini PCIe connector? When you dig deep into the Arduino Vidor Forum you find a spreadsheet with the mapping:

https://docs.google.com/spreadsheets/d/1oAL1Iz39eCHi0IVyMiTRyekmzJg5TgeyO5t0fN6Vl4U/edit#gid=0

The tab "miniPCIe pinout" shows the mapping.

Mini PCIe connector pin	Name	Number in FPGA (software)	Comment
22	PEX_RST	0
6	PEX_PIN6	1
8	PEX_PIN8	2
10	PEX_PIN10	3
12	PEX_PIN12	4
14	PEX_PIN14	5
16	PEX_PIN16	6
20	PEX_PIN20	7
28	PEX_PIN28	8
30	PEX_PIN30	9
32	PEX_PIN32	10
42	PEX_PIN42	11
44	PEX_PIN44	12
45	PEX_PIN45	13
46	PEX_PIN46	14
47	PEX_PIN47	15
48	PEX_PIN48	16
49	PEX_PIN49	17
51	PEX_PIN51	18
11	PEX_PIN11	19	this pin is only an input
13	PEX_PIN13	20	this pin is only an input
23	PEX_PIN23	21	this pin is only an input
25	PEX_PIN25	22	this pin is only an input
31	PEX_PIN31	23	this pin is only an input
33	PEX_PIN33	24	this pin is only an input

And for my test this proved to be right.

VidorBreakout board

To access the pins one could directly solder cables to the pads which is a bit tricky or use an adapter. I couldn't find a good adapter so I made my own. You can find the data here:

https://github.com/generationmake/VidorBreakout

The breakoutboard connects all GND and 3.3V pins and brings only the GPIOs seperately to the pinheader. Additionally the Vidor can be directly srewed onto the adapter with a M2.5 screw and both form a solid unit.

The design was made using 3D models and FreeCAD so that there is no collision.

The adapte follows the 2.54 mm grid of the Vidor. So both could plugged into a breadboard. Althought you would need a special breadboard because the adapter is wider that a regular breadboard.

To demonstrate the function of the GPIOs and the adapter I made a LED sequence using 17 green 3mm LEDs with a 3.3 kOhm resistor connected to ground.

Unfortunately I couldn't find any more functions which are supported on the Mini PCIe connector pins. Hopefully this changes in the future.

Boards and parts are available at Aisler: https://aisler.net/p/VKRNBJOG

Software

This is the source code of my LED sequence:

#include "VidorPeripherals.h"
#define STARTDELAY 500

void setup() {
  Serial.begin(115200);
//  while (!Serial) {}
  // Let's start by initializing the FPGA
  if (!FPGA.begin()) {
    Serial.println("Initialization failed!");
    while (1) {}
  }

  // Let's discover which version we are running
  int version = FPGA.version();
  Serial.print("Vidor bitstream version: ");
  Serial.println(version, HEX);
  pinMode(LED_BUILTIN, OUTPUT);

  // Let's also ask which IPs are included in this bitstream
  FPGA.printConfig();

  // Ok, so we know now that the FPGA contains the extended GPIO IP
  // Please refer to the online documentation for the actual pin assignment
  // Let's configure pin A0 to be an output, controlled by the FPGA
  FPGA.pinMode(0, OUTPUT);
  FPGA.pinMode(1, OUTPUT);
  FPGA.pinMode(2, OUTPUT);
  FPGA.pinMode(3, OUTPUT);
  FPGA.pinMode(4, OUTPUT);
  FPGA.pinMode(5, OUTPUT);
  FPGA.pinMode(6, OUTPUT);
  FPGA.pinMode(7, OUTPUT);
  FPGA.pinMode(8, OUTPUT);
  FPGA.pinMode(9, OUTPUT);
  FPGA.pinMode(10, OUTPUT);
  FPGA.pinMode(11, OUTPUT);
  FPGA.pinMode(12, OUTPUT);
  FPGA.pinMode(13, OUTPUT);
  FPGA.pinMode(14, OUTPUT);
  FPGA.pinMode(15, OUTPUT);
  FPGA.pinMode(16, OUTPUT);
  FPGA.pinMode(17, OUTPUT);
  FPGA.pinMode(18, OUTPUT);
  FPGA.pinMode(33, OUTPUT);
  FPGA.digitalWrite(33, HIGH);

  // The same pin can be read by the SAMD processor 
  pinMode(A0, INPUT);
  Serial.print("Pin A0 is ");
  Serial.println(digitalRead(A0) == LOW ? "LOW" : "HIGH");

  FPGA.digitalWrite(33, LOW);
  Serial.print("Pin A0 is ");
  Serial.println(digitalRead(A0) == LOW ? "LOW" : "HIGH");
}

void loop() {
  // put your main code here, to run repeatedly:
  int delaytime=STARTDELAY;

  FPGA.digitalWrite(1, HIGH);
  FPGA.digitalWrite(2, HIGH);
  FPGA.digitalWrite(3, HIGH);
  FPGA.digitalWrite(4, HIGH);
  FPGA.digitalWrite(5, HIGH);
  FPGA.digitalWrite(6, HIGH);
  FPGA.digitalWrite(7, HIGH);
  FPGA.digitalWrite(0, HIGH);
  FPGA.digitalWrite(8, HIGH);
  FPGA.digitalWrite(9, HIGH);
  FPGA.digitalWrite(10, HIGH);
  FPGA.digitalWrite(11, HIGH);
  FPGA.digitalWrite(12, HIGH);
  FPGA.digitalWrite(13, HIGH);
  FPGA.digitalWrite(14, HIGH);
  FPGA.digitalWrite(15, HIGH);
  FPGA.digitalWrite(16, HIGH);
  delay(delaytime);
  FPGA.digitalWrite(1, LOW);
  FPGA.digitalWrite(2, LOW);
  FPGA.digitalWrite(3, LOW);
  FPGA.digitalWrite(4, LOW);
  FPGA.digitalWrite(5, LOW);
  FPGA.digitalWrite(6, LOW);
  FPGA.digitalWrite(7, LOW);
  FPGA.digitalWrite(0, LOW);
  FPGA.digitalWrite(8, LOW);
  FPGA.digitalWrite(9, LOW);
  FPGA.digitalWrite(10, LOW);
  FPGA.digitalWrite(11, LOW);
  FPGA.digitalWrite(12, LOW);
  FPGA.digitalWrite(13, LOW);
  FPGA.digitalWrite(14, LOW);
  FPGA.digitalWrite(15, LOW);
  FPGA.digitalWrite(16, LOW);
  delay(delaytime);

  for(delaytime=STARTDELAY;delaytime-=100;delaytime>0)
  {
    digitalWrite(LED_BUILTIN, LOW);   // turn the LED on (HIGH is the voltage level)
    delay(delaytime);
    digitalWrite(LED_BUILTIN, HIGH);    // turn the LED off by making the voltage LOW
    FPGA.digitalWrite(1, HIGH);
    delay(delaytime);
    FPGA.digitalWrite(1, LOW);
    FPGA.digitalWrite(2, HIGH);
    delay(delaytime);
    FPGA.digitalWrite(2, LOW);
    FPGA.digitalWrite(3, HIGH);
    delay(delaytime);
    FPGA.digitalWrite(3, LOW);
    FPGA.digitalWrite(4, HIGH);
    delay(delaytime);
    FPGA.digitalWrite(4, LOW);
    FPGA.digitalWrite(5, HIGH);
    delay(delaytime);
    FPGA.digitalWrite(5, LOW);
    FPGA.digitalWrite(6, HIGH);
    delay(delaytime);
    FPGA.digitalWrite(6, LOW);
    FPGA.digitalWrite(7, HIGH);
    delay(delaytime);
    FPGA.digitalWrite(7, LOW);
    FPGA.digitalWrite(0, HIGH);
    delay(delaytime);
    FPGA.digitalWrite(0, LOW);
    FPGA.digitalWrite(8, HIGH);
    delay(delaytime);
    FPGA.digitalWrite(8, LOW);
    FPGA.digitalWrite(9, HIGH);
    delay(delaytime);
    FPGA.digitalWrite(9, LOW);
    FPGA.digitalWrite(10, HIGH);
    delay(delaytime);
    FPGA.digitalWrite(10, LOW);
    FPGA.digitalWrite(11, HIGH);
    delay(delaytime);
    FPGA.digitalWrite(11, LOW);
    FPGA.digitalWrite(12, HIGH);
    delay(delaytime);
    FPGA.digitalWrite(12, LOW);
    FPGA.digitalWrite(13, HIGH);
    delay(delaytime);
    FPGA.digitalWrite(13, LOW);
    FPGA.digitalWrite(14, HIGH);
    delay(delaytime);
    FPGA.digitalWrite(14, LOW);
    FPGA.digitalWrite(15, HIGH);
    delay(delaytime);
    FPGA.digitalWrite(15, LOW);
    FPGA.digitalWrite(16, HIGH);
    delay(delaytime);
    FPGA.digitalWrite(16, LOW);
  }
  for(delaytime=STARTDELAY;delaytime-=100;delaytime>0)
  {
    FPGA.digitalWrite(1, HIGH);
    delay(delaytime);
    FPGA.digitalWrite(2, HIGH);
    delay(delaytime);
    FPGA.digitalWrite(3, HIGH);
    delay(delaytime);
    FPGA.digitalWrite(4, HIGH);
    delay(delaytime);
    FPGA.digitalWrite(5, HIGH);
    delay(delaytime);
    FPGA.digitalWrite(6, HIGH);
    delay(delaytime);
    FPGA.digitalWrite(7, HIGH);
    delay(delaytime);
    FPGA.digitalWrite(0, HIGH);
    delay(delaytime);
    FPGA.digitalWrite(8, HIGH);
    delay(delaytime);
    FPGA.digitalWrite(9, HIGH);
    delay(delaytime);
    FPGA.digitalWrite(10, HIGH);
    delay(delaytime);
    FPGA.digitalWrite(11, HIGH);
    delay(delaytime);
    FPGA.digitalWrite(12, HIGH);
    delay(delaytime);
    FPGA.digitalWrite(13, HIGH);
    delay(delaytime);
    FPGA.digitalWrite(14, HIGH);
    delay(delaytime);
    FPGA.digitalWrite(15, HIGH);
    delay(delaytime);
    FPGA.digitalWrite(16, HIGH);
    delay(delaytime);
    FPGA.digitalWrite(1, LOW);
    delay(delaytime);
    FPGA.digitalWrite(2, LOW);
    delay(delaytime);
    FPGA.digitalWrite(3, LOW);
    delay(delaytime);
    FPGA.digitalWrite(4, LOW);
    delay(delaytime);
    FPGA.digitalWrite(5, LOW);
    delay(delaytime);
    FPGA.digitalWrite(6, LOW);
    delay(delaytime);
    FPGA.digitalWrite(7, LOW);
    delay(delaytime);
    FPGA.digitalWrite(0, LOW);
    delay(delaytime);
    FPGA.digitalWrite(8, LOW);
    delay(delaytime);
    FPGA.digitalWrite(9, LOW);
    delay(delaytime);
    FPGA.digitalWrite(10, LOW);
    delay(delaytime);
    FPGA.digitalWrite(11, LOW);
    delay(delaytime);
    FPGA.digitalWrite(12, LOW);
    delay(delaytime);
    FPGA.digitalWrite(13, LOW);
    delay(delaytime);
    FPGA.digitalWrite(14, LOW);
    delay(delaytime);
    FPGA.digitalWrite(15, LOW);
    delay(delaytime);
    FPGA.digitalWrite(16, LOW);
    delay(delaytime);
  }
  for(delaytime=STARTDELAY;delaytime-=100;delaytime>0)
  {
    digitalWrite(LED_BUILTIN, LOW);   // turn the LED on (HIGH is the voltage level)
    delay(delaytime);
    digitalWrite(LED_BUILTIN, HIGH);    // turn the LED off by making the voltage LOW
    FPGA.digitalWrite(16, HIGH);
    delay(delaytime);
    FPGA.digitalWrite(16, LOW);
    FPGA.digitalWrite(1, HIGH);
    delay(delaytime);
    FPGA.digitalWrite(1, LOW);
    FPGA.digitalWrite(15, HIGH);
    delay(delaytime);
    FPGA.digitalWrite(15, LOW);
    FPGA.digitalWrite(2, HIGH);
    delay(delaytime);
    FPGA.digitalWrite(2, LOW);
    FPGA.digitalWrite(14, HIGH);
    delay(delaytime);
    FPGA.digitalWrite(14, LOW);
    FPGA.digitalWrite(3, HIGH);
    delay(delaytime);
    FPGA.digitalWrite(3, LOW);
    FPGA.digitalWrite(13, HIGH);
    delay(delaytime);
    FPGA.digitalWrite(13, LOW);
    FPGA.digitalWrite(4, HIGH);
    delay(delaytime);
    FPGA.digitalWrite(4, LOW);
    FPGA.digitalWrite(12, HIGH);
    delay(delaytime);
    FPGA.digitalWrite(12, LOW);
    FPGA.digitalWrite(5, HIGH);
    delay(delaytime);
    FPGA.digitalWrite(5, LOW);
    FPGA.digitalWrite(11, HIGH);
    delay(delaytime);
    FPGA.digitalWrite(11, LOW);
    FPGA.digitalWrite(6, HIGH);
    delay(delaytime);
    FPGA.digitalWrite(6, LOW);
    FPGA.digitalWrite(10, HIGH);
    delay(delaytime);
    FPGA.digitalWrite(10, LOW);
    FPGA.digitalWrite(7, HIGH);
    delay(delaytime);
    FPGA.digitalWrite(7, LOW);
    FPGA.digitalWrite(9, HIGH);
    delay(delaytime);
    FPGA.digitalWrite(9, LOW);
    FPGA.digitalWrite(0, HIGH);
    delay(delaytime);
    FPGA.digitalWrite(0, LOW);
    FPGA.digitalWrite(8, HIGH);
    delay(delaytime);
    FPGA.digitalWrite(8, LOW);
  }
  for(delaytime=STARTDELAY;delaytime-=100;delaytime>0)
  {
    FPGA.digitalWrite(16, HIGH);
    delay(delaytime);
    FPGA.digitalWrite(1, HIGH);
    delay(delaytime);
    FPGA.digitalWrite(15, HIGH);
    delay(delaytime);
    FPGA.digitalWrite(2, HIGH);
    delay(delaytime);
    FPGA.digitalWrite(14, HIGH);
    delay(delaytime);
    FPGA.digitalWrite(3, HIGH);
    delay(delaytime);
    FPGA.digitalWrite(13, HIGH);
    delay(delaytime);
    FPGA.digitalWrite(4, HIGH);
    delay(delaytime);
    FPGA.digitalWrite(12, HIGH);
    delay(delaytime);
    FPGA.digitalWrite(5, HIGH);
    delay(delaytime);
    FPGA.digitalWrite(11, HIGH);
    delay(delaytime);
    FPGA.digitalWrite(6, HIGH);
    delay(delaytime);
    FPGA.digitalWrite(10, HIGH);
    delay(delaytime);
    FPGA.digitalWrite(7, HIGH);
    delay(delaytime);
    FPGA.digitalWrite(9, HIGH);
    delay(delaytime);
    FPGA.digitalWrite(0, HIGH);
    delay(delaytime);
    FPGA.digitalWrite(8, HIGH);
    delay(delaytime);
    FPGA.digitalWrite(8, LOW);
    delay(delaytime);
    FPGA.digitalWrite(0, LOW);
    delay(delaytime);
    FPGA.digitalWrite(9, LOW);
    delay(delaytime);
    FPGA.digitalWrite(7, LOW);
    delay(delaytime);
    FPGA.digitalWrite(10, LOW);
    delay(delaytime);
    FPGA.digitalWrite(6, LOW);
    delay(delaytime);
    FPGA.digitalWrite(11, LOW);
    delay(delaytime);
    FPGA.digitalWrite(5, LOW);
    delay(delaytime);
    FPGA.digitalWrite(12, LOW);
    delay(delaytime);
    FPGA.digitalWrite(4, LOW);
    delay(delaytime);
    FPGA.digitalWrite(13, LOW);
    delay(delaytime);
    FPGA.digitalWrite(3, LOW);
    delay(delaytime);
    FPGA.digitalWrite(14, LOW);
    delay(delaytime);
    FPGA.digitalWrite(2, LOW);
    delay(delaytime);
    FPGA.digitalWrite(15, LOW);
    delay(delaytime);
    FPGA.digitalWrite(1, LOW);
    delay(delaytime);
    FPGA.digitalWrite(16, LOW);
    delay(delaytime);
  }
}

Top Comments

theusbblaster over 4 years ago in reply to bernhardmayer

Hi Mr. mayer
Is it possible to use these pins as analog inputs or PWM outputs?
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bernhardmayer over 4 years ago in reply to vimarsh_

Hi Vimarsh,

thank you.

My first idea was to get more IO pins. Because with Arduino MKR I often run out of pins.

Unfortunately you only can use them as GPIOs. And the documentation is very bad. There are also PWM, I2C, UART and SPI cores in the FPGA. But these functions go only to the MKR pins. I would be no big deal to expand these cores also to the Mini PCIe connector. But Arduino hasn't disclosed all necessary source files for the FPGA so you can't impelement them on yourself. You have to rewrite the whole FPGA code. At the moment I have no plans to do this.

The second challenge was to connect the breakoutboard to the Vidor and keep the MKR pins available. I think my solution is a good compromise.

The board was designed using KiCAD.
The PCBs and parts were ordered at Aisler: https://aisler.net/generationmake/playground/vidorbreakout
And then I hand soldered the parts.

Bernhard
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vimarsh_ over 4 years ago

A great project!
This is the first time I have seen the mini PCIe of Vidor being put to use!

Just a question: Which service did you use to make that OCB?
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