Guru
Joined: 05/10/2019
Location: United KingdomPosts: 8765
| Posted: 07:53am 07 Sep 2024 |
Quick update. This is still progressing.
I've now got the proper audio filter in, which has meant doing some track rearrangement in order to handle mylar caps more easily, they can be a bit bulky. Need to trim the pot series resistors. I wish there was a simple way to change the headphone amp gain. I need it because it's doing impedance conversion to drive the headphones. Unity gain might be ok, or possibly x2. x8 is too high.
Additional components added to the HDMI socket. It's now similar to the Olimex circuit except that there are no additional data connections to the Pico. 5V at 100mA is there. I didn't modify Alpha, just Beta & Gamma.
Reset button fitted. Things like this may seem insignificant but it's important in that it proves that my SL6 macros are correct and that I can depend on them. The double USB socket was a case in point. The pins are spaced at 2.5mm,2.0mm,2.5mm distances. Don't ask me why they aren't equidistant. It caught me out.
Quite a bit of experimentation with the best way to disconnect the USB port while loading MMBasic. It really does need to be disconnected, I thought I'd got away with it. I'm still uncertain about cutting down a micro USB lead for the Pico 2. I think I'm going to have to specify a micro USB plug breakout board. Chopping a lead can result in a few 2-core cable ends before you find the right one! It's either that or hard wire the USB to TP2 and TP3 as I'm currently doing.
Some fairly major work was done in increasing the depth of the PCB beyond the maximum size given by Hammond. That left too much of a gap and meant that some components couldn't fit into the front and rear panel holes.
I've been tweaking the manual too, adding component photos.
Discovered what CR1220 batteries are for. You can superglue the holder on top of a clock chip and use it to convert a disposable RTC into one with a changeable battery. :)