Re: Bus Pirate "Ultra" v1a & v1b with ICE40 and Icestorm :)
Reply #1 –

You may have noticed that most of the components on the bottom edge of the v1a are not populated. That's because when we started working the design it was obvious that we could push it a lot further with a few tweaks.
First, we dropped the ADC, Vpu, and 3.3V pins. We added 3 more IO pins, giving us 8 IO total. What do you know, that matches the 8 channels available from the logic analyzer
Instead of measuring voltage through a dedicated ADC pin, we used an 74xx4015 8:1 analog mux and a op-amp to add low impedance voltage measurement to ALL the IO pins. Woot!
Next, we used the DAC from the MCU to margin a Microchip voltage regulator to get a 0.8volt to 5.0volt adjustable output power supply. This new "Vout" pin replaces the 5volt pin. Bam!
Finally, we double up the 4066s to add optional pull-up resistors to all 8 IO pins. The pull-ups are now powered by the output of the adjustable power supply, or by an external voltage applied to Vout. All the outward-facing buffer logic is also powered in the same way using the Vout pin.
1. MOSI
2. CLOCK
3. MISO
4. CS
5. AUX
6. AUX2 (formerly ADC)
7. AUX3 (formerly Vpullup)
8. AUX4 (formerly 3.3Volts)
9. 0.8-5.0Vout/Vref (formerly 5.0Volts)
10. GND
This is our new pinout
Routing on this board is still in progress, but we hope to be stuffing it by early September.