The Toadstool

Description

The Toadstool is designed to make your prototyping life easier and faster.

I was looking to break away from dev-boards and start building my own mare-metal microcontroller projects. After wiring up an MCU on a breadboard a few times I realised it's messy and not much fun. The Toadstool gives you a leg-up by allowing you to easily and quickly get the MCU onto the breadboard, without sacrificing flexibility.

The first round of prototypes are designed for the ATmega328P and the MSP430-G2553

While I was at it, I designed a standard header. This will allow breakout modules (I call them CAPs) to be added to the Toadstool without creating rats-nests of wires or using up precious breadboard space. This header includes SPI/I2C/TWI/UART.

Details

I wanted to achieve a few things with the Toadstool:

Win back the flexibility that some dev boards (like the Arduino) don't give you
Plug directly into a breadboard to make breadboard-based MCU projects quick to get going
Allow a range of microcontrollers to be used
Allow I2C, SPI and UART breakout modules to easily be connected to any of the Toadstool boards

Currently there are 2 Toadstool boards in the works:

Toadstool mega328: Based on the Atmel ATmega328P
Toadstool MSPg2553: Based on the TI MSP430G2553

Key design features:

The shape: move all the supporting components out of the way of the breadboard, to maximise use of the limited breadboard space.
Power: an on-board regulated power supply, allowing you to select the operating voltage. Polarity and over-current protection./
Speed: Select the crystal that works best for your specific project (ATmega only)
DIP: Where possible I'll be using DIP packages. A little more bulky, but you can switch your MCU out.
CAPs: Breakout modules can be connected to a standard I2C/SPI/UART header

Toadstool CAPs

These are the breakout modules that connect to the board's common header. Here's a cap, and how it connects:

Currently working on :

EEPROM 24LC: an I2C interface EEPROM module (Microchip 24LC128)
RTC MCP79400: an Real Time Clock modules (Microchip MCP79400)
USB-UART 2200: a USB to UART converter (Microchip MCP2200)

I'll keep updates coming in the project log. Thanks for the interest!

Project Logs

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Prototype #2 Tested
Andrew Retallack • 06/04/2015 at 07:02 • 0 comments
A second batch of PCBs arrived from China a couple of weeks ago, and I've had a chance to assemble and test them. Apart from a few minor cosmetics on the silkscreen, I'm happy with the outcome - the gallery has been updated with latest images.
What changed:
- Toadstool CAP headers changed to provide better stability
- Broke out the Reset pin into the Toadstool CAP header
- Low-profile SMD reset button, so it can be pressed with a Toadstool Cap mounted
- Aluminium caps now replace the tantalum ones
- Silkscreen and layout tweaks
Where to from here?
I'm testing the range of Toadstool CAPs that arrived in the same shipment:
- an EEPROM module based on the Microchip 24LC128
- a RTC using in the Microchip MCP79400
- a USB-Serial converter using the Microchip MCP2200 (having a bit of trouble with this one!)
ATmega Prototype #1 Tested
Andrew Retallack • 04/29/2015 at 05:53 • 0 comments
The ATmega328P prototype of the Toadstool arrived a month ago and has been through some solid testing. Here it is assembled:
I found a couple of usability issues with the physical layout which I've corrected:
- The 2x6 header for the "Toadstool Caps" (breakout boards) has been split into two 1x6 headers to add stability to the Cap
- The reset switch has been switched (!) for an SMD low profile version to prevent the Toadstool Cap from obscuring it.
- The Tantalum caps have been replaced by Aluminium ones to make the board more reflow friendly (listen to this great podcast on capacitors)
- A number of changes to silkscreen to make it more readable