Continue to Site

# low cost picstick_25k50 platform with programming via USB mass storage

#### enkilo

##### Newbie
I have found these two underrated but almost unknown projects "picstick_25k50" and "USB-Stack"
They're easily manufactured with low part count and can be made by soldering novices.

It is the cheapest possible opensource microcontroller I know of. The circuit board is small, made with through-hole parts and can be used on breadboard, using wire-wrap or with JST connectors which makes it ideal for experimenting and building sophisticated machines.
The PIC18F25K50 is a very capable $2 microcontroller with builtin USB, an internal oscillator up to 64MHz and many analog peripherals. The cost for a small lot of 20 picsticks is as low as$5 per unit. Because of the internal oscillator a quartz can be omitted. The same goes for the costly USB plug and cable because the USB connector is directly on the print board.
There are two bootloaders for it. One is from the Pinguino IDE, an opensource programming environment close and compatible to Arduino. The other makes the "picstick" appear as USB thumb drive to which you can drag & drop a new program as a .HEX file. For this mode the button needs to be pressed while plugging it into the USB. When programmed, the picstick can then be either powered by USB or independently from a 3.7V lithium battery.

libpicp and pictest are two skeleton projects, for writing software libraries and programs compatible across a range of PIC12/16/18 and across the sdcc and the xc8 compiler.
from the author of the USB-uC bootloader is also the USB-Stack project which contains templates for USB devices like MIDI and HID using xc8 and MPLAB IDE.

Hardware layouts

OSH Park PCB service

USB Stack for making picstick appear as USB device (for MIDI etc.)
PIC18F25K50 datasheet

Library for different PICs (16F876A, 18F252, ....)

Test programs for different PICs

#### Attachments

• photo_2022-08-20_20-10-18.jpg
450.7 KB · Views: 37
• photo_2022-08-20_20-10-25.jpg
407.1 KB · Views: 27
• picstick_25k50_v1.brd.png
22.2 KB · Views: 23
• picstick_25k50_v1.sch.png
82.1 KB · Views: 23
• picstick_layout.jpg
57.2 KB · Views: 26