7-segment display used required new footprint: created and placed. Tests indicate caravel may be clocked up to about 28MHz, osc changed to 20MHz. Added a DNP pull-up for nRST, just in case internal isn't around or doing the job. DNPed PMODs.
Fix for bring-up discovery of Caravel reset issue. The pull-up on the ~RESET pin is insufficient for stable power-up: it rises along with the supply and glitches operation. Tests show adding a cap to delay transition looks sufficient for decent boot.
Also exposed the slow clock config/enable using jumper (J12)
Minor tweaks for pick&place and silkscreen adjustments.
Component replacements for PCBA/costing and related layout work.
- Tactile switches swapped out for bigger components
- LDOs swapped out for more efficient components
- USB-C connector changed for unit that only handles power
- layout positioning of 1 symbol -> 2 placements for carrier board
Rework and complete re-route for the TT 1-3 mainboard.
- Flipped the input DIP switch so physical and logic match-up (ON is high)
- Fix: reset and clock only affect project, i.e. mapped to in 0 and 1
- Fix: debouce circuits reworked, positive edge on button press
- Mapped Caravel HK SPI to Pico
- Remapped external pin headers
- Removed resistor networks as we can rely on caravel pull-downs
- Routed such that manual remap of output to 7-segment display won't involve avoiding traces while cutting jumpers
Mainboard for TT 01, 02 and 03 released, with DIP switches for inputs and selection, PMOD I/O, 7-segment display and Raspberry Pi Pico footprint.
This is the preliminary release of the schematic, for review and prototyping.