With the HDD Synth prototype MKIII design completed it's now just a question of waiting for PCBWay to complete the PCB manufacturing and assembly process. Because they're attaching the surface mount components and a number of the through hole components, it could take a few weeks to complete.
So in the meantime, I thought I'd keep myself busy and start working on the FDD Synth
It's been a very interesting one to research and determine which approach to use.
With the HDD Synth it simply listens for a binary on/off signal in terms of drive access and then plays a sound of random access. For the FDD Synth I wanted something more realistic. Something that mirrored exactly how you'd expect the FDD to sound depending on what it was doing.
To achieve this I'm making it attach to the FDD cable which allows it to listen in on the activity of the FDD on the cable. The FDD cable consists of 34 pins. For each data pin, it has a corresponding ground pin.
Because I only want to observe the activity of the commands being sent to the FDD that result in it making a sound, I can listen to a subset of these. Those being:
- Pin 8 - Index: Active once per revolution of the disk
- Pin 10 - Motor enable A: Active when drive A is spinning
- Pin 12 - Drive select B: Active when commands are being sent to drive B
- Pin 14 - Drive select A: Active when commands are being sent to drive A
- Pin 16 - Motor enable B: Active when drive B is spinning
- Pin 18 - Direction: High means the head is moving outwards, Low inwards
- Pin 20 - Step: Each pulse is a movement of the head
- Pin 26 - Track 00: Head has reached the inner most track
By monitoring these pins it's possible to simulate a FDD in software as it'll know if the drive is spinning along with the position and movement of the head. This allows for the creation of very realistic sounds that mirror how the drive is being used.
I'm designing the FDD Synth to be as small and cheap to manufacture as possible. So unlike the HDD Synth MKIII it won't feature as physical controls and will need to be configured by settings on the SD card.
The small design means it'll be possible to add it into non-PCs like the Amiga 500. However it'll also have an optional 3.5" drive bay mount that will also house the speaker.
I'm playing with the idea of creating a pin header on it that will allow for an optional control panel to be attached, giving it various controls and the option for an OLED screen.
All the hardware and software designs are Open Source to be used for learning and modification. Once I've proven the design and polished it I'll make it available for sale.
