Wednesday, April 23, 2014

Minima - CPU Module Mock-up

As stated is the previous post, I was concerned that maybe the JTAG header could interfere with the LCD display. A mock-up would be necessary verify clearance.
Minima CPU
Mock-up to Check JTAG Clearance
The mockup was done with a simple print of the layout, with headers pressed into a Styrofoam block. The display is supported by the header pin at the top and the two nylon screws as legs in the lower corners. Because this is an experimental device, additional constraints are not necessary. The header at the top left, is for BAND switching.
LCD Display Header
The JTAG 6 pin heard (2x3) is located beneath the LCD display. When in the JTAG header is in use, the LCD display will not be used, and therefore removing the LCD will not be a problem. In fact because the JTAG Programming process used a few of the same pins as those used but the LCD, removing the LCD avoids any interaction concerns.

Checking JTAG Clearance below LCD Display
(viewed from the left)
The LCD Display sets at a slight angle forward for the users viewing benefit.

The mock-up revealed an additional concern, the header on the right end of the module should be moved up a little to avoid the nylon screw. The two header on this end are the SSB Mode and Si570 control headers.
The Two Pin Herder Will be Moved to the Right
(viewed from the right)
The spacing between the LCD and front push switches appears about right for easy access. The header at the bottom is (left to right), AUX-CTL for the Minima Audio sections, the Tuning Pot, and the Programming header.
Push Button Switch will be
Mounted in Font of the LCD Display
(as viewed from User Respective)
With much research, I have discovered there are many JTAG header standards in use, some have as many as 20 pins. The high pin count JTAG headers are used for monitoring as well as In Circuit Programming. I will use the simple six pin header and configuration that is used by the Arduino.

With maybe only slight modifications, I am pleased with the layout and mock-up results.


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