[Arm-netbook] libre hardware

[Muhammed Adel Afzal]

I misunderstood; when Mr. Ross said "congratulations Chris", I thought that he meant Christopher Waid (who is working with Luke I think).  I misunderstood your "blush" as a joke, taking Chris Waid's credit.  It's awesome that you contributed to the Micro Desktop PCB; that sounds like a significant and valuable contribution to me.

Thank you Chris Havel,

Adel



----- Original Message -----
From: "Christopher Havel" <laserhawk64 at gmail.com>
To: "Linux on small ARM machines" <arm-netbook at lists.phcomp.co.uk>
Sent: Thursday, August 25, 2016 11:14:57 PM
Subject: Re: [Arm-netbook] libre hardware

@ Mr Afzal -- I designed a relatively insignificant portion of the video circuitry. It appears on the Micro-Desktop PCB. I consider it a bit of a kludge -- it's effective, but only by brute force. It's hobbyist grade stuff... then again, I'm a hobbyist, so I suppose it's to be expected... 

90% of it was taken straight from Wikipedia's article on the subject; all I did was calculate values for some passives and IIRC provide a way of turning part of it off. 

Basically it's a DAC -- digital to analog converter. It converts the TTL-level (0-5v) pulses off the CPU card to the 0-0.7v analog voltages required for the RGB lines on the VGA port. It's the cheap and nasty R-2R resistor ladder kind of DAC. Sure, it's inexpensive, but it'd give any real electronics engineer a cringe and a shudder. Dave Jones (EEVBlog on YouTube) would quite likely pop a gasket if he saw such a job in anything professional, and quite honestly I somewhat agree with him. I want to say the ability to switch between 16bit and 24bit color was done with a couple of 74xx logic chips, but I don't remember offhand which ones I used. (Forgive me, it's been a couple years.) 

The honest truth is that the triple-fistful of passives in there should be replaced by a trio of dedicated flash-DAC chips -- far less crude and far more effective. 

I'm proud of the work in an "I contributed to a cool thing" sort of way, but that's really the only way I'm proud of it. It's not something to be proud of in terms of design, that's for sure... 

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