Thursday, 16 June 2011

FTDI's Vinculo Development Board: A Review

I was lucky enough to get involved in the Farnell/element14 'road test' programme, where individual electronic hobbyists get a chance to review (and keep) cool hardware items from Farnell.

If you don't know it already, element14 ( is a community/networking site for electronics professionals and hobbyists, run by the electronic components supplier Farnell...

Last year I was lucky enough to attend a really useful free Eagle (PCB Design Tool) course run by element14, and earlier this year my local hackspace, BuildBrighton, reached the final of the Great Global Hackspace Challenge which was sponsored (very generously) by element14.

While other suppliers might give out samples and freebies to industry, its refreshing that Farnell/element14 really do seem to be actively targetting and supporting the electronics hobbyist/hacker community - and so I am more than happy to sing their praises here.

Anyway, back to my road testing... I chose to review the VNCLO-START1 kit from FTDI. This kit is made up of a USB development board and a separate programmer/debugger board and the current cost on Farnell's web site is a little under £28.

The development board is branded the Vinco/Vinclo/Vinculo/Vnclo (it seems that FTDI aren't sure about the name yet, but I will call it “Vinculo”) containing the 64-pin version of FTDI's VNC2 'Vinculum' USB Host/Slave chip.

Very interestingly, FTDI have given the board the same form factor as an Arduino Uno, including pin-compatible Arduino shield header sockets and even an on-board ADC chip to provide the six analog inputs. This means that you should be able to make use of existing Arduino shields (add on boards) with the Vinculo, which is a clever move by FTDI.

The Vinculo can emulate an Arduino because it's on-board VNC2 chip is so much more than just a USB controller... its a fully fledged MCU. In fact it's a very powerful one, with a 16-bit core, 256kB of Flash, 16kB of RAM and 48Mhz clock among some other nice features... This makes it substantially more powerful that the AVR chip on the Arduino....And that’s before we get on to its USB support: Two full speed USB ports, each individually configurable as host or slave!

So, we're talking an impressive piece of silicon (and a reasonably priced one, with the 64-pin VNC2 chips selling on Farnell's site for just over £3, which is cheaper than the Atmega328).

I am planning to use VNC2 chips in two projects I have in the pipeline:

  • The first to USB-host a Novation Launchpad keypad controller and run a suite of animation/MIDI-input apps. The idea is to make a standalone version of my 'playpad' MIDI controller projects.
  • The second is as the 'brain' of my laser projector, where I need a high speed USB device to push coordinate data from a PC to a pair of DACs driving laser-projector galvos. Using a VNC2 means I can use a single chip (no need for separate USB chip and MCU) while avoiding the slowness of a polled USB stack implemented in software.

The Vinculo board seems like the perfect way to prototype these projects... so how to get started?

FTDI have a free, downloadable developer toolchain for the VNC2. This works with the VNC2 programmer/debugger to allow programming and interactive debugging of the Vinculo. And I really do mean interactive debugging... single stepping, breakpoints, watches and so on... controlled via USB to the debug board.. put that in your Arduino pipe and smoke it :)

So that's all good news, but once I got started I found a few problems with the developer tools which made me think FTDI may not be quite there yet...

First of all I was unable to use the IDE on my desktop computer (where I do all my coding) because of a strange display problem with the source code editor window - all the text becomes garbled and unreadable each time the window scrolls. I reported this to FTDI support who quickly got back with a 'That’s strange, we'll look into it' kind of response but no fix as yet. However, luckily my laptop doesn't get the same issue so I could move on.

The second issue I found was stability of the IDE, particularly during debug sessions but even some times when compiling, the IDE would stop responding and needs to be killed in task manager and restarted.

Moving on, I played a bit with some of the provided sample code. The Vinculo is not FTDI's first VNC2 evaluation board, and some of the sample code is for the older eval board, which has different pin to connector mappings, meaning that the older sample programs don't work on the Vinculo without modifications. For example the UART (used by the sample programs for debug output) has moved.

Luckily the remapping can be done in software.... a very nice feature of the VNC2 is that all the IO's go through a programmable multiplexer, so IO functions can be assigned to pins of your choosing. However the need to reassign IO's just to get the sample programs to work isn't what you want when you're first starting with a new device.

Another niggle is that while there are sample programs provided to demonstrate standard Arduino stuff (blinking LED, PWM examples and so on) what is glaringly lacking are any USB code examples that will work, without modification, on the Vinculo. Since USB is the attraction of Vinculo over vanilla Arduino I think this is something FTDI need to work on to make the board attractive to Arduino fans... I am still trying to work out how to modify the USB examples to get them running on Vinculo, and its not been straightforward.

On a more positive note, something FTDI have done is to create a simple application framework that should appeal to Arduino coders by presenting an Arduino-like syntax.... For example, when using the supplied main.c in your Vinculo project you define the Arduino standard entry points 'setup' and 'loop'.

Arduino-likey function wrappers like digitalOut() are provided, and libraries like Serial are emulated with structures containing function pointers, so familiar Arduino syntax like Serial.begin(9600); can be used.... Its just syntactic sugar, since behind the scenes the VNC2 API functions are being called, and its not 100% compatible (don't expect your Arduino code to 'just work' on Vinculo). However, it's a nice idea and will certainly appeal to Arduino developers. And you are still free to simply ignore it and work directly with the VNC2 API if you prefer.

FTDI also have a variety of documentation for online download, which I am still working my way through. I have to say the information seem to be a bit 'scattered' over many different application notes, but at least it mostly seems to be there. Its just a bit daunting and confusing when you first get started.

In conclusion, I have to say I'm very excited by this hardware. The VNC2 is a powerful and flexible chip, and the Vinculo is a great prototyping board, encompassing some innovative ideas by FTDI.

However, at the moment I think much could be improved in the accompanying development software package. For me it has been a uphill struggle, and I think that Arduino users who are not experienced coders may fall at the first hurdle with this.. that is until FTDI can iron out the IDE issues and provide a more consistent and usable set of Vinculo code samples.

This is a new product though, so I have hopes that these things will improve soon with software patches.

A couple of other things that would be nice are
  • That Arduino staple - The always-useful pin 13 LED
  • The ability to direct debug text output over the same USB cable that runs the debugger, where is can perhaps show up as a virtual COM port on the host PC (like on the mbed).
I will post again soon with my progress applying the Vinculo/VNC2 to my own projects... watch this space!

Monday, 6 June 2011

Solenoid Percussion for BuildBrighton's Noise Toys Event

Last monday, BuildBrighton (my local hackspace) along with Playgroup (Brighton arts and events collective), ran “Noise Toys”... a day of making noisy gadgets in a local pub, anyone welcome – as part of the Brighton festival fringe.

At BB we were intending to provide a selection of “sound sculptures” around the place, but in the end we only managed a couple, which included my Lava-Lamp modulated synthesiser and an “interactive solenoid percussion” thing, which I'll give you the low-down on here

My idea was to have some MIDI triggered solenoid percussion (similar to together with some kind of control surface to allow passing punters to control the solenoids and make little tunes and rhythms.

I thought it would be fun to use my Novation Launchpad to control the solenoids.

The Launchpad is a grid of illuminated buttons that is intended as a controller for Ableton Live (music app), but like most things it can be hacked :)

A while back I made a little Windows-based program to run a “rain storm” sequencer on the Launchpad (as seen on Basically this was a simple step sequencer where notes are triggered by pressing buttons on the Launchpad and they “fall” - only sounding when they hit the bottom of grid. Pressing buttons on the lower row toggles them between Green (notes in the column are played then cycled back to top of grid) and Red (note plays once and does not cycle)

To add to the challenge (and because I needed the laptop to run Reason for the Lava Lamps) I thought it would be nice to be able to run the rain storm sequencer without the computer....

The Launchpad is a USB device (it doesn't have 5-pin MIDI connectors) so something would be needed to work as a “USB host” to allow a program running on a microcontroller (Arduino, PIC etc) to listen out for button presses and to control the Launchpad lights while sending out MIDI notes to trigger the solenoids.

I'd thought about making my Launchpad into a standalone MIDI controller before, and I had been looking at the FTDI VNC2 USB host chip (more about that later) but first of all I decided to try out the Sure Electronics USB HID Host Module which is based around a PIC and is a little short of £10 on eBay including the postage.

Sure's board is a nice little module, with 0.1” headers for the PICKit programmer and for serial comms with other application hardware. It also has a USB Type-A (host) socket and couple of addressable LED's. The on-board PIC24FJ256GB110 supports “USB On the go” (OTG) which means it can act as a USB host. Sure's web-site has downloadable source code for a firmware app, based Microchip's own open-source USB host stack, that will host a standard USB mouse or keyboard.

The only disappointment here is that only a minimal set of I/Os from the PIC are bought out through the headers which limits applications of the board since most of the PICs I/Os are inaccessible. Still, its a nice handy board and reasonably priced. But will it work with the Launchpad?

The Launchpad is not a standard USB MIDI or HID device. Rather it has a custom interface using two interrupt endpoints. This can be accommodated on the PIC with a couple of mods to the “Generic” device driver code from Microchips stack. It was my first time working with USB hosting and with 16-bit PICs so it was a learning experience.

When used under Windows via the Novation drivers, the Launchpad shows up as a MIDI device and is controlled by sending it MIDI note and controller info to toggle the LEDs. When Launchpad's buttons are pressed, it spits out MIDI notes/controllers which an application can act on.

So that the MIDI interface from Windows but exactly is happening on the USB wire? Well, a quick bit of trace code on the PIC showed that exactly the same MIDI bytes are being passed between the USB endpoints, making it nice and easy to drive the Launchpad from an embedded USB host like the PIC. Thankyou, Novation!

So on to the Rainstorm sequencer program, which I wanted to run on the same PIC. The sequencer code itself is pretty simple, but there are some complications when using Microchip's USB host stack which meant it took a while to get it working....

The main gotcha for me was that USB I/O operations need to be first initiated then polled for completion (or they can send completion events). However, to keep the stack ticking, the app must poll it via a “USBTasks” function. Without this polling, the stack does nothing and I/O will not complete. Ok, so just call USBTasks all over the place right? No sireeee, not if you don't want to end up in a confusing re-entrant mess and watch the PIC collapse in a heap.

In fact you need to be careful not to make USBTasks call anywhere but the top level loop, and to make sure that the application attempts just one USB I/O operation between USBTasks calls. One result of this is that long sequences of USB I/Os can become painfully slow to complete. With the Rainstorm sequencer I found that it became very sluggish at responding to input when there were more than a couple of dozen notes in play.

I am looking forward to trying this on the FTDI VNC2 chip which has the USB stack and application running in separate threads and should be able to get much better throughput.

OK – back to the fun and games! So the UART from the PIC is broken out to the header on the Sure Electronics board, and with the code changed to set up the correct MIDI baud rate and remove all other UART debug output from the code I could just stick on a 5-pin DIN socket via a couple of 220R resistors and I was sending MIDI.

On the other end of the MIDI connection I had a breadboard with a PIC16F688 receiving MIDI through a 6N138 isolator and triggering 8 digital outputs (each mapped to a MIDI note from the sequencer). Each output goes through a 1K resistor to a TIP120 NPN power transistor which directly drives a solenoid. The solenoids need about 18 volts to work properly so there's a 7805 and smoothing caps between the 18V side and the 5V logic side. I also had a hefty cap (2200uF) smoothing the 18V side since the solenoids can cause some big voltage dips when they fire all at once and this can reset the PIC. The schematic is available here

Once all the electronics was working it was time for the art... and unfortunately I didn't leave myself much time for that bit. I ended up gathering up milk bottles and hammering together a wooden frame for them to sit on, all the night before the gig. I had for some reason assumed that milk bottles, tuned with water, would make a pleasing “xylophone” effect... I hadn't really anticipated the the terrifying wall of machine gun clinking that they actually threw out.

Hmmm, well, there is always next time :)