USB to USB keyboard converter

[hasu]

This is not an keyboard protocol converter in fact, but with this you can change keymap and use functions TMK firmware offers on your USB keyboard. https://github.com/tmk/tmk_keyboard#features

This depneds largely on Circuit@Home USB Host Shield 2.0 and its Arduino library.
https://github.com/felis/USB_Host_Shield_2.0



Hardware
You need USB host controller chip MAX3421e and AVR chip ATMega32U4.

The easiest way is buying my TMK USB to USB converter



1. TMK USB to USB converter
This small board includes all functions of Host Shield and Leonardo. No soldering job is needed.

you can buy an assmebled converter here to support my project.
https://geekhack.org/index.php?topic=72052.0

More

PCB design files are available.
https://github.com/tmk/USB2USB_Converter

Case design file is available here. Thank you, Gouty@github! 2018-10/27 New!
https://github.com/tmk/USB2USB_Converter/tree/master/3D%20Printed%20Case



2. USB Host Shield 2.0 + Arduino Leonardo
This firmware work with Circuit@Home USB Host Shield + Arduino Leonardo as well, they are not small for keyboard converter but work well.

a. USB Host Shield:
Get official one to support USB Host Shield project! From these links you can get genuine shield.
https://www.circuitsathome.com/products-page/arduino-shields/usb-host-shield-2-0-for-arduino-assembled/
http://shop.tkjelectronics.dk/product_info.php?products_id=43

Clones may have compatiblity issues with the library and TMK. Not recommended.
https://github.com/felis/USB_Host_Shield_2.0/issues/76#issuecomment-159269359
And you cannot use SparkFun USB Host Shield which is not compatible to Leonardo.

b. Arduino Leonardo:
http://arduino.cc/en/Main/arduinoBoardLeonardo



3. Mini USB Host Shield 2.0 + Pro Micro
Also Pro Micro 3.3V or Teensy with mini host shield will work with some fixes on signal/power routing.

https://www.circuitsathome.com/products-page/arduino-shields/usb-host-shield-for-arduino-pro-mini
https://www.sparkfun.com/products/12587
https://www.pjrc.com/teensy/td_libs_USBHostShield.html

TBD



Firmware
This converter is part of TMK keyboard firmware project.

https://github.com/tmk/tmk_keyboard/tree/master/converter/usb_usb

Build
You can compile firmware from source code. See TMK documentation for the detail.

Code: [Select]

$ git clone git://github.com/tmk/tmk_keyboard.git
$ cd tmk_keyboard
$ git submodule init
$ git submodule update
$ cd converter/usb_usb
$ make clean
$ make

To reduce firmware size you can disable functions you don't use by commenting out following lines. Note that 'make clean' is needed after Makefile is editted.

NKRO is meaningless practically on this converter and it should be disabled always.

Code: [Select]

# Build Options
#   comment out to disable the options.
#
MOUSEKEY_ENABLE ?= yes # Mouse keys
EXTRAKEY_ENABLE ?= yes # Media control and System control
CONSOLE_ENABLE ?= yes # Console for debug
#COMMAND_ENABLE ?= yes    # Commands for debug and configuration
#NKRO_ENABLE ?= yes # USB Nkey Rollover
https://github.com/tmk/tmk_keyboard/blob/master/converter/usb_usb/Makefile#L93-L97

No idea? No problem, you can use easy TMK keymap editor instead, see below.


Program
For TMK converter
First, boot your converter into programming mode or bootloader by pressing button on it.

To program converter with your firmware install 'dfu-programmer' and run this with 'sudo' if needed.

Code: [Select]

dfu-programmer atmega32u4 erase --force
dfu-programmer atmega32u4 flash <your_firmware.hex>
dfu-programmer atmega32u4 reset

If you have installed build tools you can just 'make' like this.

Code: [Select]

make dfu

You can use Atmel FLIP as well on Windows. Also refer this wiki page.
https://github.com/tmk/tmk_keyboard/wiki#flash-firmware



For USB Host Shield 2.0 + Arduino Leonardo
Push reset button on Leonardo before run this command. Serial port name(COM17) depends your system. On Linux I got /dev/ttyACM0.

Code: [Select]

$ DEV=COM17 make program
or
$ avrdude -patmega32u4 -cavr109 -b57600 -Uflash:w:usb_usb.hex -PCOM17



TMK Keymap Editor
USB to USB converter supports TMK keymap editor now!

You can edit keymapping and get your custom firmware easily with this.



Try it here.
http://www.tmk-kbd.com/tmk_keyboard/editor/unimap/?usb_usb
SpaceFn on editor: http://goo.gl/5kvPrl


(Old editor: http://www.tmk-kbd.com/tmk_keyboard/editor/usb_usb/   SpaceFn: http://bit.ly/1OqgvMn )





Limitation

• Only supports 'HID Boot protocol'(6KRO) mode. It is theoretically possible to support NKRO mode but I won't add it. NKRO keyboard shall work in 6KRO mode. (Confirmed NKRO keyboards: TMK Alps64, Massdrop Infinity 60%, Novatouch)
• Media/System control keys on keyboard are not recognized by the converter. Note that you can still send those keys with TMK firmware.
• 'Fn' key on keyboard is not recognized. In most case keyboards don't spit out keycode for the key. You cannot remap 'Fn' key itself while 'Fn' combination keys can be remmapable. Note that you can still define 'Fn' key with TMK firmware.
• Firmware size. USB to USB converter uses alot of flash space to support USB keyboard. Some combination of TMK features can not fit into MCU flash size(28KB)[/url]. To reduce firmware size you have to disable some of features you don't use, see 'Firmware' section above.
• To work with Sprit's PCB you have to force USB mode(Auto PS/2-USB mode selection doesn't work with the converter)
• No mouse or other pointing devices support. To support all pointing devices is difficult but it is possible to support one specific device if you are willing to write code for that. https://geekhack.org/index.php?topic=69169.msg2193024#msg2193024

Incompatible Keyboards
The converter doesn't work with:

• Varmilo VA87MR
• GON's NerD
• Kinesis Advantage2
• FC660C (it works now!)
• Realforce RGB (work around) Fixed now 2018-07-08
• GMK
• Tean Wolf
• Ace Pad
• X-Keys Foot Pedal XF-10-US
• G80-3000 with 2KRO(due to Cherry firmware bug) Patched for the bug. 2018-08-01
• Xiaomi Yuemi MK02S

Compatible Keyboards
If your keyobard works well with BIOS/EFI you can expect the converter handle it reasonably.

• Realforce
• Realforce RGB
• HHKB Pro/JP
• HHKB Pro2 working on USB Hub issue
• LEOPOLD FC660C
• LEOPOLD FC980C
• LEOPOLD FC750R
• Varmilo MA109C
• Lenovo SK-8855(ThinkPad keyboard. TrackPoint is not supported.)
• KBP V60-MTSQ
• Cherry G80-3600
• Filco Majestouch2(Tenkeyless 87-key)
• Ducky One TKL
• Microsoft Sidewinder X4
• Novatouch
• TMK Alps64
• Input Club/Massdrop Infinity 60%
• LinDon Tech 68 key
• Apple aluminium keyboard
• G80-3000
• HyperX FPS Pro keyboard
• Mionix Wei
• ikbc KD87
• Logitech Unifying(K230)
• DXT28 Bluetooth HID Proxy dongle

Please post your result in this thread. 'USB descriptor' would be helpful for debug if your keyboard doesn't work.
Refer this for how to get 'USB descriptor'. https://github.com/tmk/tmk_keyboard/wiki/USB-Descriptor



TODO

DONE:

• Force NKRO keyboard in 6KRO mode. I believe most of NKRO keyboards also supports 6KRO. With future update NKRO keyboard will work with the converter in 6KRO mode but currently NKRO keyboard doesn't work. Library itself sends SetProtocol(boot) request so NKRO keyboard should work if it supports boot protocol(6KRO). DONE
• Standard LED indicators support. Caps Lock, Scroll Lock and Num Lock indicators. DONE

Update
2018/11  Update firmware(Use fixed LUFA stack and update USB_Host_Shield_2.0)
2018/11  Add Filco Majestouch2 87 and ikbc KD87 to compatility list
2018/07  Update  firmware to fix startup issue. see this commit.
2018/10  Add design file for enclosure
2018/02  Update "Reported keyboards" section
2017/05  Fix startup code for FC660C
2016/09  New keymap editor(unimap) is available
2016/01  Add Keymap editor
2015/12  Add Firmware size to limitations, and recommendation for genuine host shield
2015/11  Add keymap for JIS and ISO
2015/07  Bug fix for keyboard sending ErrorRollOver report
2015/07  Add Locking key indicator support
2015/06  Updated Limitation and TODO
2015/02  TMK USB to USB converter Rev.A
2014/12  Added Hub support(confirmed with HHKB pro2)

[TheSoulhunter]

Nice! Interested in getting one...

[SpAmRaY]

Hasu, any chance you would build some of these to sell?

[metalliqaz]

This is really great. I wanted to build one of these a while ago but I just couldn't find the time to follow through.  Looks fantastic!

[hasu]

I have spare PCBs and have a plan to get some of them assembled once I confirm it works well in the field after some daily usage.

Today, I found a bug

[nubbinator]

That's really cool.  How do you change the keymapping with it?

[hasu]

I can't live without mousekey and layer switching with space bar

https://github.com/tmk/tmk_keyboard/blob/master/converter/usb_usb/keymap_hasu.c

[hasu]

I'm having power or/and initializing related problem during plugin and bootup time
This problem occurs on both my converter and leonardo and Host shield(old Sparnkfun one),  at this point not sure it is firmware problem or hardware one.

Once the problem is sorted out I'd run small distribution(GB) from my spare PCBs.

[spiceBar]

I'm having power or/and initializing related problem during plugin and bootup time
This problem occurs on both my converter and leonardo and Host shield(old Sparnkfun one),  at this point not sure it is firmware problem or hardware one.

Once the problem is sorted out I'd run small distribution(GB) from my spare PCBs.

Wow! I had missed this thread!

I have purchased the Arduino and USB Host shield some time ago, compiled and uploaded TMK, and it worked. Then the plan was to implement SpaceFN and GuiFN on it, but I have not done it yet due to lack of time.

How is this project going?

I'm very interested in purchasing a few assembled controllers from you, if you have enough of them available.

[hasu]

Not sort the problem yet I've worked on other projects like alps64 and HHKB Alt Controller.

Probably it is not hardware but initialization in firmware problem. I'll look into soon.

Unfortunately this converter requires two chips and it costs much and assembly process takes long. But it works it is important!

Kudus to Circuit@Home!

[njbair]

This is really cool. Would this pass enough current to power a model m or similar along with a PS/2 adapter? I would love TMK features in a model m.

[hasu]

Unicomp USB keyboard?
How you can draw current is depends on your USB host capability. I think you can use Unicomp USB Model M as far as your PC or Hub can supply power enough.

BTW, What do you need TMK features actually?

[spiceBar]

Not sort the problem yet I've worked on other projects like alps64 and HHKB Alt Controller.

Probably it is not hardware but initialization in firmware problem. I'll look into soon.

Unfortunately this converter requires two chips and it costs much and assembly process takes long. But it works it is important!

Kudus to Circuit@Home!

I'm not sure how much it costs, but for me price is not an issue. After spending so much on mechanical keyboards, fine-tuning them thanks to your wonderful adapters is a really great addition.

Will we be able to purchase completely assembled converters from you?

I think it would be interesting to be able to purchase some without the USB plugs. I think the converters are thin enough to install them inside most keyboards, provided we solder the "in" and "out" wires directly to the small PCB. If it's not possible, I hope it's not too difficult to desolder the USB plugs.

[njbair]

Unicomp USB keyboard?
How you can draw current is depends on your USB host capability. I think you can use Unicomp USB Model M as far as your PC or Hub can supply power enough.

BTW, What do you need TMK features actually?

I've got a PS/2 Model M and I use an adapter like this. But I think PS/2 boards draw a lot of current. Just wondering if your device would supply enough current for PS/2.

[hasu]

Finally sorted out the bootup problem, yay!
It was a intilization problem of firmware, not hardware. It is lucky that I can still use existent PCB and components.

I'll start making a few boards soon and create GB or artisan service thread for this converter.

I'm having power or/and initializing related problem during plugin and bootup time
This problem occurs on both my converter and leonardo and Host shield(old Sparnkfun one),  at this point not sure it is firmware problem or hardware one.

Once the problem is sorted out I'd run small distribution(GB) from my spare PCBs.

[gosinger]

Wow...great project, this thread made me register here...

looking forward to future development, keep up the great work! I'll get myself an Leonardo and will give this a go

[Leimi]

Finally sorted out the bootup problem, yay!
It was a intilization problem of firmware, not hardware. It is lucky that I can still use existent PCB and components.

I'll start making a few boards soon and create GB or artisan service thread for this converter.

I'm having power or/and initializing related problem during plugin and bootup time
This problem occurs on both my converter and leonardo and Host shield(old Sparnkfun one),  at this point not sure it is firmware problem or hardware one.

Once the problem is sorted out I'd run small distribution(GB) from my spare PCBs.

Great job, looking forward to it

[Thumper_]

Will you be able to change the keypad so it transmit properly keypad numcodes?

[njbair]

Will you be able to change the keypad so it transmit properly keypad numcodes?

If the keypad is currently sending out exactly the same scancodes as the number row, this adapter will have no way to tell them apart.

[Thumper_]

Will you be able to change the keypad so it transmit properly keypad numcodes?

If the keypad is currently sending out exactly the same scancodes as the number row, this adapter will have no way to tell them apart.

And on a standalone keypad?

[njbair]

Will you be able to change the keypad so it transmit properly keypad numcodes?

If the keypad is currently sending out exactly the same scancodes as the number row, this adapter will have no way to tell them apart.

And on a standalone keypad?

I have not used this but I believe in that case it would work.

[hasu]

I started an artisan service thread for my TMK keyboard converters. And I'll assmeble some USB to USB converters soon and taking order tentatively now, check this post if someone is interested in taking my converter.
https://geekhack.org/index.php?topic=72052.msg1759680#msg1759680

I have to decide the price later due to final cost calc, but you can cancel it if you don't like the final price.
The price will be around 40-50USD, probably.

[hasu]

Updated Limitation and TODO in first post.

In short:
NKRO keyboards doesn't work with the converter at this time but they will be supported in 6KRO mode with future update. Also Lock indicators support will be added by firmware upgrade.

NKRO mode and System and Media Control keys are not supported. And 'Fn' or 'Pn' key on keyboard like Poker cannot be handled by the converter.



BTW, some assembled TMK USB to USB converters are available now here.
https://geekhack.org/index.php?topic=72052.0

[berserkfan]

Updated Limitation and TODO in first post.

In short:
NKRO keyboards doesn't work with the converter at this time but they will be supported in 6KRO mode with future update. Also Lock indicators support will be added by firmware upgrade.

NKRO mode and System and Media Control keys are not supported. And 'Fn' or 'Pn' key on keyboard like Poker cannot be handled by the converter.



BTW, some assembled TMK USB to USB converters are available now here.
https://geekhack.org/index.php?topic=72052.0

As a custom layouts guy I am eagerly watching and waiting for the day when your USB to USB converter will have LED support.

[hasu]

Small update: Added locking key indicator(LED) support and fixed for Rollover error of 2KRO keyboard.

2015/07  Bug fix for keyboard sending ErrorRollOver report
2015/07  Add Locking key indicator support

https://github.com/tmk/tmk_keyboard/commit/6f5e8ce17e89005130cd0f9ecc6e346a77bb624b
https://github.com/tmk/tmk_keyboard/commit/1efdd867c8f88ad779ad82e1b22df62bf6be8fe9

[argcargv]

Testing with Kinesis Advantage, spacefn is working!!!

[hasu]

Great!

BTW, I did this just for fun and it worked with daisy chain of two, at least

[njbair]

Great!

BTW, I did this just for fun and it worked with daisy chain of two, at least

Show Image

Seeing this pic just made me realize how awesome this project is. Imagine being able to throw this thing into your backpack, and everywhere you go you've got your preferred keyboard layout and function layers, no matter what keyboard you're forced to use. Amazing.

[ctm]

Wow! This is so amazing! So is this like a keycode translator? Does it also work on keys than don't send keycode (like fn)?

[njbair]

Wow! This is so amazing! So is this like a keycode translator? Does it also work on keys than don't send keycode (like fn)?

From the OP:

'Fn' key on keyboard is not recognized also. In most case keyboards don't spit out keycode for the key. Note that you can still define 'Fn' key with TMK firmware.

So unfortunately no. But if your board can be programmed so that the Fn key sends a keycode, just do that.

[hasu]

Wow! This is so amazing! So is this like a keycode translator? Does it also work on keys than don't send keycode (like fn)?

From the OP:

'Fn' key on keyboard is not recognized also. In most case keyboards don't spit out keycode for the key. Note that you can still define 'Fn' key with TMK firmware.

So unfortunately no. But if your board can be programmed so that the Fn key sends a keycode, just do that.

Right. 'Fn' key itself cannot be remmaped while combination of 'Fn' and some keys(for example, Fn+x, Fn+w,...) are probably remappable.

[kirkvomit]

Hi, does anyone has tested usb to usb converter for a long time?
Mine is made from Leonardo board.
And I have a problem that converter stops registering any inputs after few days.
Restart of the board doesn't help. Plug unplug some times helps for a 5 minutes and then controller stops registering inputs again.
Tried on different PCs, result is the same, it works flawlesly for few days and then starts glitching.

Have somebody faced this problem too?

[hasu]

And I have a problem that converter stops registering any inputs after few days.
Restart of the board doesn't help. Plug unplug some times helps for a 5 minutes and then controller stops registering inputs again.

Interesting.
I've not experienced that situation so far, but I pluged converter a day at most. hmm, I can't come up any clue from that description. More informations would be useful to speculate the problem.

What is your converter hardware actually? Circuit@Home shield or other? Leonardo is genuine one or clone?

What is your host? Desktop, notebook? OS?

what is your keyboards?

Can you post logs when it happened?

Your firmware is the latest? And post files if you changed something.

And you can use hid_listen to see how converter stops.

[kirkvomit]

Leonardo is clone from ebay.
Shield is like this one http://www.ebay.com/itm/USB-Host-Shield-Support-Android-ADK-UNO-MEGA-Duemilanove-2560-For-Arduino-/201354197970?hash=item2ee1a53bd2

Tried on 2 PCs and one notebook, all have Ubuntu 14.04 installed.
Keyboards are poker 2 and razer blackwidow tournament.

What logs did you mean?
Firmware is not latest, I flashed it may be in aprill 2015.
Can you explain about hid_listen?

I will try to flash it with latest firmware without any changes and will let you know if it fixed the problem or not.

[hasu]

Logs are located under /var/log/, you can find something related to USB in kern.log, IIRC.

As for hid_listen, see these. And google with word 'hid_listen' to find download link.
https://github.com/tmk/tmk_keyboard#debugging
https://github.com/tmk/tmk_keyboard/wiki/FAQ#debug-console

Yeah, try the latest firmware and report back.

[njbair]

Do magic and bootmagic work with this converter?

[hasu]

No. This and other TMK converters probably can't check key state while their startup time.

Bootmagic is supported only with TMK keyboard controllers while Magic command works on both converters and keyboard controllers.


https://github.com/tmk/tmk_keyboard/issues/175

[njbair]

No. This and other TMK converters probably can't check key state while their startup time.

Bootmagic is supported only with TMK keyboard controllers while Magic command works on both converters and keyboard controllers.


https://github.com/tmk/tmk_keyboard/issues/175

I can't seem to get Magic to work. Do I need to enable it at compile time first? I couldn't find any make flags for that.

For bootmagic, your issue suggests a startup delay as a workaround. If this were a configurable option, like a make flag, that would be a really good solution because only those who explicitly enable the delay will have to wait for it.

[hasu]

No. This and other TMK converters probably can't check key state while their startup time.

Bootmagic is supported only with TMK keyboard controllers while Magic command works on both converters and keyboard controllers.


https://github.com/tmk/tmk_keyboard/issues/175

I can't seem to get Magic to work. Do I need to enable it at compile time first? I couldn't find any make flags for that.

For bootmagic, your issue suggests a startup delay as a workaround. If this were a configurable option, like a make flag, that would be a really good solution because only those who explicitly enable the delay will have to wait for it.

To enable Magic commands this line is required in Makefile.

Code: [Select]

COMMAND_ENABLE = yes    # Commands for debug and configuration


[sandric]

How do you program this converter? I mean if you want to remap some key you unplug keyboard from female usb port and plug it strickly to usb port of computer, or it is doable with keyboard connected to it? And what is language you program - arduino C? Uploading with arduino ide? Isn't library Arduino USB Host?

[njbair]

I wrote a nice long review of this converter because I'm so in love with it right now.

Thanks for your work, hasu!

[hasu]

Nice writeup! Thanks.
I subscribed the thread.

[njbair]

I bought an off-brand Leonardo & shield (both made by SainSmart). I was able to flash the .hex file with avrdude without any errors, but it's not working as a converter at all.

What steps can I take to debug this thing?

[hasu]

They seem to be compatible to original boards but the shop doesn't offer technical details like schematic enough to make certain of. Let's say they are compatible.

http://www.sainsmart.com/sainsmart-usb-host-android-adk-shield-2-0-for-arduino-uno-mega-r3-mega2560-duemilanove-nano-robot.html
http://www.sainsmart.com/sainsmart-leonardo-r3-atmega32u4-development-board-for-arduino.html#customer-reviews

Can you see debug message with hid_listen?
Keyboard is given enough voltage?


BTW, I haven't confirm my firmware with original Circuit@Home board. I'm using Sparkfun shield(with modification) and genuine Leonardo besides my own TMK converter.
https://www.sparkfun.com/products/9947

[njbair]

They seem to be compatible to original boards but the shop doesn't offer technical details like schematic enough to make certain of. Let's say they are compatible.

http://www.sainsmart.com/sainsmart-usb-host-android-adk-shield-2-0-for-arduino-uno-mega-r3-mega2560-duemilanove-nano-robot.html
http://www.sainsmart.com/sainsmart-leonardo-r3-atmega32u4-development-board-for-arduino.html#customer-reviews

Can you see debug message with hid_listen?
Keyboard is given enough voltage?


BTW, I haven't confirm my firmware with original Circuit@Home board. I'm using Sparkfun shield(with modification) and genuine Leonardo besides my own TMK converter.
https://www.sparkfun.com/products/9947

hid_listen recognizes the SainSmart Leonardo. When I plug it in, it says

Code: [Select]

Listening:
init: done
keyboard_set_led: 05

That last line is accompanied by all three lock LEDs on my keyboard quickly flashing. After this, nothing happens. Typing on the keyboard does nothing. If I unplug the keyboard from the USB host shield and plug it back in, the lock LEDs flash again. But no message about LEDs this time in hid_listen.

hid_listen always stays connected to the first device it finds until it's unplugged or deactivated, even when you plug another device in. I have a working hasu converter as well. I wanted to test whether the Leonardo was crashing or freezing:

run hid_listen
plug in Leonardo: hid_listen initializes the Leonardo properly
plug in hasu's converter: nothing changes
leave hasu's converter plugged in and unplug Leonardo: hid_listen initializes hasu's converter properly
plug in Leonardo: nothing changes
unplug hasu's converter: hid_listen initializes Leonardo properly

This tells me the Leonardo stays connected as HID, so it's not freezing or crashing.

This must be an issue with the USB host shield. It may be a pin incompatibility with the original, or it may be that the shield itself is DOA.

Maybe I can upload a simple Arduino sketch to test that the USB host shield is working. If so, it may be that the shield is not compatible with the Sparkfun shield you used for testing, hasu.

[hasu]

It seems like communication between Leonardo and PC works well.

Does the keyboard work with TMK converter?
And did you check voltage USB host shield supplies?


Yes, 'hid_listen' is connected just to first device found. To connect it to another device you need to disconnect the first device. This is cofusing a bit when you are using some devices with custome firmware like TMK and Soarere's.

[njbair]

It seems like communication between Leonardo and PC works well.

Does the keyboard work with TMK converter?
And did you check voltage USB host shield supplies?


Yes, 'hid_listen' is connected just to first device found. To connect it to another device you need to disconnect the first device. This is cofusing a bit when you are using some devices with custome firmware like TMK and Soarere's.

I have not checked the host shield voltage yet. I'll have to wait until next week to try that though, as the converter is at the office.

[njbair]

Well, I checked the host shield voltage yesterday, only to determine after spinning my wheels for about an hour, that my multimeter is in terrible need of recalibration.

Fortunately, I was eventually able to solve the problem with the Leonardo & USB host shield. The host shield uses a few pins on the ICSP header, but my USB host shield did not include female headers on those pins (even though the product image shows it with headers). I had some spares lying around so I was able to solder on my own headers and now it works like a charm. Now I just need a nice enclosure and some time to play around with LEDs.

So I can confirm, that if you can afford the time to solder and have some spare headers, this is a slightly cheaper way to build your own converter. Just know that hasu's pre-made converter is much smaller and you're supporting his wonderful work!

SainSmart Arduino Leonardo clone: http://smile.amazon.com/dp/B00CO07PNY
SainSmart USB Host Shield: http://smile.amazon.com/dp/B006J4G000
Female 0.1" headers (if you need them): http://smile.amazon.com/dp/B007Q84C4O

[hasu]

Great.

But really terrible story with SainSmart, and you are not alone
http://www.amazon.com/gp/customer-reviews/R13EEDLP8OWUA4/ref=cm_cr_pr_viewpnt?ie=UTF8&ASIN=B006J4G000#R13EEDLP8OWUA4

The host shield uses a few pins on the ICSP header, but my USB host shield did not include female headers on those pins (even though the product image shows it with headers).  I had some spares lying around so I was able to solder on my own headers and now it works like a charm.

[njbair]

Great.

But really terrible story with SainSmart, and you are not alone
http://www.amazon.com/gp/customer-reviews/R13EEDLP8OWUA4/ref=cm_cr_pr_viewpnt?ie=UTF8&ASIN=B006J4G000#R13EEDLP8OWUA4

The host shield uses a few pins on the ICSP header, but my USB host shield did not include female headers on those pins (even though the product image shows it with headers).  I had some spares lying around so I was able to solder on my own headers and now it works like a charm.

I saw that. That review, along with a forum post on the Arduino website, led me to discover the problem.

The worst part is, once I knew the problem I tried searching really hard to find any kind of documentation from SainSmart that I might have missed, but there's nothing. It seems like their only documentation is the product descriptions on their store and Amazon.com. What a pity.

See, kids, this is why you should buy your converters direct from hasu!