Cheapest / lower parts count mCU with USB

Hi,
 
  I am looking for the cheapest (I'm trying to cost reduce a hobby project just for fun) with usb and high current sink/source (20*15ma would be great) that requires a the minimal amount of external components (the mcu will be deadbug wired in order to make it fit into a small cube and save cost)

  I eliminated many crystal-less usb able PICs mcu because they require several external capacitors, and searching for crystal-less one is not easy on microchip.com . Atmega16U4 seems nice (only 2 resistors needed), but I could not source it for les than $4.5 including shipping, when arduino pro mini can be bought in china for $2.35 including shipping (but is 33.5mm wide, and will require diods for vusb)

  any idea ?

th,
eliott.

On 27/05/14 09:13, eliott.gentil@gmail.com wrote:
> Hi,
> 
> I am looking for the cheapest (I'm trying to cost reduce a hobby
> project just for fun) with usb and high current sink/source (20*15ma
> would be great) that requires a the minimal amount of external
> components (the mcu will be deadbug wired in order to make it fit
> into a small cube and save cost)
> 
> I eliminated many crystal-less usb able PICs mcu because they require
> several external capacitors, and searching for crystal-less one is
> not easy on microchip.com . Atmega16U4 seems nice (only 2 resistors
> needed), but I could not source it for les than $4.5 including
> shipping, when arduino pro mini can be bought in china for $2.35
> including shipping (but is 33.5mm wide, and will require diods for
> vusb)
> 
> any idea ?
> 
> th, eliott.
> 

Are you planning on making dozens or hundreds of these?  If it is a
one-off, I would have thought $4.50 would not be an unreasonable
investment in a hobby.  For a single piece, it's going to be hard to get
significantly less when shipping and handling is included.

Do you need a USB host or device?
What USB version?

> Are you planning on making dozens or hundreds of these?  If it is a

I'am going to make 4-5 for myself, and may do a kit/kickstarter if people are interested. Anyway, $4.50 is acceptable, but part of the fun of this project is to try to make it for dead cheap.

Currently, it only cost a few smd leds and resistors, 20cm of 1.5mm� wire, a spoon of synthetic plaster, a few centimeters of magnet wire and a micro usb connector. Total cost is less than $2.

By adding an mcu I could :
-Ask for 250mA when the device is connected to a computer and not and usb wall adapter (this is mondatory, though nobody does it)
-Add an animation on the leds.
-Add an usb protocol to upload custom animations

Rising total price from $2 to $4.50 just for that is not really great. I could use a $1 mcu to make the animation, let it be programmed via UART and forget about gently asking for 250mA.

Once again, $4.5 is not overpriced, but the fun is to do the whole thing on the cheap :)

Eliott.

Le mardi 27 mai 2014 12:51:18 UTC+2, Dave Nadler a �crit�:
> Do you need a USB host or device?
> 
> What USB version?

It is an USB device. First need is to ask for the 250mA I will use, second need is to have an easy firmware or data upgrade of the device. Slow 1 endpoint hid or CDC would be enough.

For now, the 'best' solution is V-USB on an Atmega8A, but a crystal-less solution would be nice since I will use air wiring.

Quick update :

Current winner seems to be PIC16F1459 : It just needs 2 capacitors, has 14kb of flash, 18 I/O pins and 1kb of ram. The cheaper PIC16F1454 is good too, but only has 14 I/O pins and no ADC (that may provide better capacitive touch sensing than the digital version).

Cost for 10 SOIC pieces from microchip is about $25 including 3 day shipping to europe (QFN or SSOP). $23.30 from Chinese sellers, 3 weeks shipping. 

Hi,

also have a look at the C8051F383 (or C8051F38C): 32KB (or 16KB) FLASH,
2KB RAM and 25 I/O pins.

Rene

On 5/27/2014 6:53 AM, azepoiazepoi@gmail.com wrote:
>> Are you planning on making dozens or hundreds of these?  If it is a
>
> I'am going to make 4-5 for myself, and may do a kit/kickstarter if people are interested. Anyway, $4.50 is acceptable, but part of the fun of this project is to try to make it for dead cheap.
>
> Currently, it only cost a few smd leds and resistors, 20cm of 1.5mm� wire, a spoon of synthetic plaster, a few centimeters of magnet wire and a micro usb connector. Total cost is less than $2.
>
> By adding an mcu I could :
> -Ask for 250mA when the device is connected to a computer and not and usb wall adapter (this is mondatory, though nobody does it)
> -Add an animation on the leds.
> -Add an usb protocol to upload custom animations
>
> Rising total price from $2 to $4.50 just for that is not really great. I could use a $1 mcu to make the animation, let it be programmed via UART and forget about gently asking for 250mA.
>
> Once again, $4.5 is not overpriced, but the fun is to do the whole thing on the cheap :)

A bigger problem than the USB interface might just be the high current 
drive I/O.  Many MCUs provide a handful of high drive I/Os, but few 
provide 20 of them.  They often restrict the total current drive if not 
the individual line drive capability.

If you are making 5 of these and others will be buying 1 or 2 each, you 
will do better focusing on ways to reduce the postage costs than the MCU 
costs.

-- 

Rick

On 5/27/2014 7:33 AM, azepoiazepoi@gmail.com wrote:
> Le mardi 27 mai 2014 12:51:18 UTC+2, Dave Nadler a �crit :
>> Do you need a USB host or device?
>>
>> What USB version?
>
> It is an USB device. First need is to ask for the 250mA I will use, second need is to have an easy firmware or data upgrade of the device. Slow 1 endpoint hid or CDC would be enough.
>
> For now, the 'best' solution is V-USB on an Atmega8A, but a crystal-less solution would be nice since I will use air wiring.

What about *no* MCU, but a USB chip that gives you I/O ports instead and 
let the PC do the heavy thinking?  Is it FTDI that makes a part with 
either UARTs, JTAG or GP I/O?  I think it has a CPU inside and if you 
ask nicely enough they will let you program that.

-- 

Rick

On 5/27/2014 8:22 AM, Ren� K�nig wrote:
> Hi,
>
> also have a look at the C8051F383 (or C8051F38C): 32KB (or 16KB) FLASH,
> 2KB RAM and 25 I/O pins.
>
> Rene
>
AAAHAHAHAHAHAHAHAHA  I thought 8051 was dead  ;-)