In this short series of posts, I have looked at alternative processors to the ATmega1284 for my "Neo-Retro" Computing platform - based on my WiNode 5 and EVITA board stack.
WiNode 5 - shown below, has a 40 pin DIL socket located in the centre of the pcb. The position of the signal pins on this socket are arranged so as to accommodate a Atmel ATmega1284 - as this is a commonly available, reasonably low cost AVR device with 128Kbytes of Flash and 16Kbytes of RAM. It also has the added advantage of two uarts, SPI, I2C and 3 interrupt lines - making it kind of a "super-Arduino".
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| WiiNode 5 with ATmega1284 40 pin DIL version fitted |
However the socket was not solely intended for the ATmega1284. It is for generic access to the hardware on the WiNode board - and so any microcontroller, fitted to a suitable 40 pin carrier board, may be fitted in this position.
Recently, in this Blog, I explained how the 40 pin DIL package was a neat way of packaging up some of the smaller microcontrollers, so a s to make them more manageable in the form of a plug in module - that does not require difficult SMT soldering. This time I take a closer look at the 40 pin format - and show how it can be used to our benefit, for a number of different applications.
As a teenager, growing up in the very early 1980s, the 40 pin DIL was the only format that microprocessors came in. It was a convenient size that could carry a 16 bit address bus, an 8 bit data bus, a few control lines and power. Some manufacturers even copied the pin-out of their competitors' devices - so that they could swap their devices for their superior device - although this practice usually ended in law suits. However, it's not a bad idea to have a common footprint amongst devices - making the upgrade path very simple.
So with this in mind I have decided to do something similar, and make a series of compatible modules that allow the user to move conveniently between processor families.
A Common Template for a Microcontroller Plug-In
Making a plug-in module is a fairly trivial process - it's just a small piece of pcb with a standard pinout, which acts as a chip carrier for whatever devices are needed in the design. I did this a couple of years ago with my STM32F373 based ARMiGo project.
First we look at the template for the proposed module. You will recall that the ATmega1284 is available as a DIL 40 package - and its arrangement of ports allows form a very logical layout with power pins at the centre - which prevents disasters, should you happen to get the IC into the socket the wrong way around! So by the miracles of ASCII-Art in plain courier font we have the package template.
An MSP430 FRAM Variant for WiNode 5
Last week, whilst waiting for some pcbs to come back from manufacture I had a quick look at the MSP430 range of microcontrollers - especially those in the MSP430FR5xxx series which have non-volatile ferroelectric memory.
This time I look at some of the more practical aspects of using these interesting SMT devices.
These are available in a relatively easy to use 38 pin TSSOP package, so the plan was to make a neat little TSSOP to 40 pin DIL adaptor board - so that they may be used with breadboards and stripboards.
After a little thought, and a few hour's with EagleCAD, I came up with the following layout. The device is uncluttered - for once, I am not trying to squeeze every last component onto a small board.
The board carries the MCU, and external SPI memory device, a 32kHz crystal, Reset Button, User Button and a LED. In addition there is an external SPI memory device - which can be FRAM (up to 256Kbytes) or SRAM (up to 128Kbytes).
As a teenager, growing up in the very early 1980s, the 40 pin DIL was the only format that microprocessors came in. It was a convenient size that could carry a 16 bit address bus, an 8 bit data bus, a few control lines and power. Some manufacturers even copied the pin-out of their competitors' devices - so that they could swap their devices for their superior device - although this practice usually ended in law suits. However, it's not a bad idea to have a common footprint amongst devices - making the upgrade path very simple.
So with this in mind I have decided to do something similar, and make a series of compatible modules that allow the user to move conveniently between processor families.
A Common Template for a Microcontroller Plug-In
Making a plug-in module is a fairly trivial process - it's just a small piece of pcb with a standard pinout, which acts as a chip carrier for whatever devices are needed in the design. I did this a couple of years ago with my STM32F373 based ARMiGo project.
First we look at the template for the proposed module. You will recall that the ATmega1284 is available as a DIL 40 package - and its arrangement of ports allows form a very logical layout with power pins at the centre - which prevents disasters, should you happen to get the IC into the socket the wrong way around! So by the miracles of ASCII-Art in plain courier font we have the package template.
ATmega1284 Package
________________
B0 |o 1 o| A0 A I
B1 |o o| A1 n n
INT2 B2 |o o| A2 a p
PWM0A B3 |o o| A3 l u
PWM0B B4 |o o| A4 o t
MOSI B5 |o o| A5 g s
MISO B6 |o o| A6 u
SCK B7 |o o| A7 e
/RESET |o o| AREF
VCC |o o| GND
GND |o o| AVCC
XTAL2 |o o| C7
XTAL1 |o o| C6
RXD1 D0 |o o| C5
TXD1 D1 |o o| C4
RXD2 D2 |o o| C3
TXD2 D3 |o o| C2
PWM1A D4 |o o| C1 SDA
PWM1B D5 |o o| C0 SCL
PWM2A D6 |o o| D7 PWM2B
| Note that the power pins are in the centre of the package and offset - so cannot be reversed accidentally. Additionally the ports A,B,C,D are neatly stowed in a way that makes navigating around the pinout very easy - it's all done for maximum simplicity. I have also labelled the key signals - so when it comes to layout the new processor module - it's a case of matching up function on a pin by pin basis. With the template for the package in place, it is now possible to lay-out any small processor in this format. My interest lies in two (or possibly three) candidates. Firstly the 38 pin TSSOP MSP430FR5759 secondly the 48 pin LQFP STM32Fxxx ARM M4 Cortex device. Both of these will be capable of a significant improvement in processing throughput over the original ATmega1284. |
An MSP430 FRAM Variant for WiNode 5
Last week, whilst waiting for some pcbs to come back from manufacture I had a quick look at the MSP430 range of microcontrollers - especially those in the MSP430FR5xxx series which have non-volatile ferroelectric memory.
This time I look at some of the more practical aspects of using these interesting SMT devices.
These are available in a relatively easy to use 38 pin TSSOP package, so the plan was to make a neat little TSSOP to 40 pin DIL adaptor board - so that they may be used with breadboards and stripboards.
After a little thought, and a few hour's with EagleCAD, I came up with the following layout. The device is uncluttered - for once, I am not trying to squeeze every last component onto a small board.
The board carries the MCU, and external SPI memory device, a 32kHz crystal, Reset Button, User Button and a LED. In addition there is an external SPI memory device - which can be FRAM (up to 256Kbytes) or SRAM (up to 128Kbytes).
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| A simple 40 Pin DIL Breakout Module for the MSP430FR5739 and MSP430FR59xx devices |