It’s been a while since my last update on this project. This has largely been due to a month or so of big weeks at work delivering to a project deadline, and lots of family commitments in my personal time. Work is returning to normal now, so I’m hoping to sneak in a bit of progress on this and another couple of projects before the Christmas madness hits.

I’ve pretty much finished the board assembly now. I’ve just been waiting on the replacement 74HC4053 chips as I had mistakenly ordered SOIC wide i.e. 7.9mm wide instead of the standard 3.9mm  wide SOIC in my first digikey order  – doh!

Putting together this last Digikey order was a huge task. I feel like I need to find a better process / workflow for managing my BOM. It was quite a complicated process to keep track of what parts I need, for this revision, vs what was in the original BOM, minus what I have in stock… There must be an easier way than the spreadsheet/filter nightmare I’ve just been through so if anyone has suggestions please let me know!

Here is the board in it’s current state:

Mostly assembled board

I have a bunch of firmware development tasks I can work on with this revision:

• PWM control of the FAN (Intel FAN control spec)
• Dithering of DAC output
• Read back of the output voltage using the external ADC
• Monitoring of the input voltage using the MCU ADC
• Temperature reading
• Serial protocol for UART / USB interface
• Rotary encoder reading for user input
• ILI9341 320×240 TFT LCD display for user interface

Hopefully I should be able to get the bulk of of the firmware development done with the rev 0.1 board.  In parallel I’m going to start laying out rev 0.2 which will include the full regulator for the low voltage (8V at up to 8A) version.

I had initially thought that I may have to do a couple of prototypes of just the digital control portion before I started on the full board including the analog regulator circuit. However, I now think I may be able to get away with just the one version. Time will tell once I have got further into the firmware development.

One thing I have now realised is that I have messed up some of the pin allocations for the STM32 in rev 0.1 as some of the functions have conflicts. Hopefully I’ll be able to move some of the allocations around a bit and be able to stick with the STM32F070CBT6 part and not have to move up to a higher pin count device. I have a few unallocated pins to play with and  could potentially move the DAC and ADC to the same SPI master if I need to recover more, so I have some ideas about how to tackle this issue.