Changes suggested for Rev1

[josuah]

This is an attempt at collecting all changes discussed for the Rev2

[josuah]

Pico pinout change

Changing the board pinout to avoid use of RP2040 GPIO15, flawed in the RP2040 hardware:

Pico pinout

RP2040      Rev1                                 Rev2
          ┌─────────────────┐                  ┌─────────────────┐
GPIO0     │ ICE_SO          │ FPGA             │ IOT_38b UART RX │ Pico
GPIO1     │ ICE_SSN         │ programming      │ IOT_36b UART TX │ ICE40
GPIO2     │ ICE_SCK         │ interface        │ IOB_23b         │ shared
GPIO3     │ ICE_SI          │                  │ IOB_29b         │ bus
          ├─────────────────┤                  │                 │
GPIO4 TX  │ IOT_38b UART RX │ Pico             │ IOT_39a         │
GPIO5 RX  │ IOT_36b UART TX │ ICE40            │ IOT_37a         │
GPIO6     │ IOB_23b         │ shared           │ IOB_25b_G3      │
GPIO7     │ IOB_29b         │ bus              │ IOB_31b         │
          │                 │                  ├─────────────────┤
GPIO8     │ IOT_39a         │                  │ ICE_SO          │ FPGA
GPIO9     │ IOT_37a         │                  │ ICE_SSN         │ programming
GPIO10    │ IOB_25b_G3      │                  │ ICE_SCK         │ interface
GPIO11    │ IOB_31b         │                  │ ICE_SI          │
          ├─────────────────┤                  ├─────────────────┤
GPIO12    │ PICO_PMOD_A     │ Pico             │ PICO_LED_R SDA  │ LED / I2C
GPIO13    │ PICO_PMOD_A     │                  │ PICO_LED_G SCL  │
          │                 │ PMOD             ├─────────────────┤
GPIO14    │ PICO_PMOD_A     │                  │ SRAM_SSN        │ SRAM CS
          │                 │ PMOD             ├─────────────────┤
GPIO15    │ PICO_PMOD_A     │                  │ PICO_LED_B      │ LED
          │                 │                  ├─────────────────┤
GPIO16    │ PICO_PMOD_B     │                  │ PICO_PMOD_A     │ Pico
GPIO17    │ PICO_PMOD_B     │                  │ PICO_PMOD_A     │ PMOD
GPIO18    │ PICO_PMOD_B     │                  │ PICO_PMOD_A     │
GPIO19    │ PICO_PMOD_B     │                  │ PICO_PMOD_A     │
          ├─────────────────┤                  │                 │
GPIO20    │ SRAM_SSN        │ SRAM CS          │ PICO_PMOD_B     │
          ├─────────────────┤                  │                 │
GPIO21    │ IOT_46b_G0      │ ICE_CLK          │ PICO_PMOD_B     │
          ├─────────────────┤                  │                 │
GPIO22    │ PICO_LED_R      │ LED              │ PICO_PMOD_B     │
GPIO23    │ PICO_LED_G      │                  │ PICO_PMOD_B     │
          │                 │                  ├─────────────────┤
GPIO24    │ PICO_LED_B      │                  │ IOT_46b_G0      │ ICE_CLK
          ├─────────────────┤                  ├─────────────────┤
GPIO25    │ PICO_CLKOUT     │ Clock PMOD       │ Clock PMOD      │
          ├─────────────────┤                  ├─────────────────┤
GPIO26    │ ADC0/CDONE      │ ADC / ICE_DONE   │ ADC / ICE_DONE  │
          ├─────────────────┤                  ├─────────────────┤
GPIO27    │ ADC1/CRESET     │ ADC / ICE_RSTn   │ ADC / ICE_RSTn  │
          ├─────────────────┤                  ├─────────────────┤
GPIO28    │ ADC2            │ extra            │ ADC2 / PB       │ extra
GPIO29    │ ADC3            │ ADCs             │ ADC3            │ ADCs
          └─────────────────┘                  └─────────────────┘

[josuah]

[EDIT] swapping the SRAM CS with the PICO_LEDs to avoid GPIO15 and get a hardware I2C peripheral

[vr2045]

Done...

[josuah]

Shield board pins

Coarse placement of the pins, their number and pinout may be change as wished:

  ,─────────────────────────────────.    ,─────────────────────────────────.
 /.───. ( ) ( ) ( ) ( ) ( ) ( ) .───.\  /.───. ( ) ( ) ( ) ( ) ( ) ( ) .───.\
. │   │       S P A R E S       │   │ .. │   │       S P A R E S       │   │ .
│ '───' ( ) ( ) ( ) ( ) ( ) ( ) '───' ││ '───' ( ) ( ) ( ) ( ) ( ) ( ) '───' │
│                        ┌───┐  J7    │├───────┐                ┌───┐┌───────┤
│  LED3    ┌─────┐       ├SJ1┤    o   ││( ) ( )│                ├SJ1┤│( ) ( )│
│          │ SW2 │       └───┘        │├───────┘                └───┘└───────┤
│( ) [ ]   └─────┘   LED2      ( ) [ ]││( ) [ ]             LED2      ( ) [ ]│
│                                     ││                                     │
│( ) ( )                       ( ) ( )││( ) ( )                       ( ) ( )│
│        I                   I        ││        I                   I        │
│( ) ( ) C                   C ( ) ( )││( ) ( ) C                   C ( ) ( )│
│        E                   E        ││        E                   E        │
│( ) ( ) | ┌───────────┐     | ( ) ( )││( ) ( ) | ┌───────────┐     | ( ) ( )│
│        A │           │     S        ││        A │           │     S        │
│( ) ( )   │           │       ( ) ( )││( ) ( )   │           │       ( ) ( )│
│          │ ICE40UP5K │              ││          │ ICE40UP5K │              │
│( ) ( )   │           │       ( ) ( )││( ) ( )   │           │       ( ) ( )│
│          │.          │              ││          │.          │              │
│( ) [ ] I └───────────┘       ( ) [ ]││( ) [ ] I └───────────┘       ( ) [ ]│
│        C            o               ││        C            o               │
│( ) ( ) E┌─┬─┐┌─┬─┐ TP1       ( ) ( )││( ) ( ) E┌─┬─┐┌─┬─┐ TP1       ( ) ( )│
│        |│SJ5││SJ6│                  │├───────┐|│SJ5││SJ6│          ┌───────┤
│( ) ( ) H└─┴─┘└─┴─┘           ( ) ( )││( ) ( )│H└─┴─┘└─┴─┘          │( ) ( )│
│                                     ││       │ ┌─────┐             │       │
│( ) [ ]                       ( ) [ ]││( ) ( )│ │ SW2 │             │( ) ( )│
│                                     │├───────┘ └─────┘             └───────┤
│( ) ( )                       ( ) ( )││( ) ( )                       ( ) ( )│
│        I   ┌───────────┐   P        ││        I   ┌───────────┐   P        │
│( ) ( ) C   │           │   I ( ) ( )││( ) ( ) C   │           │   I ( ) ( )│
│        E   │           │   C        ││        E   │           │   C        │
│( ) ( ) |   │  RP2040   │   O ( ) ( )││( ) ( ) |   │  RP2040   │   O ( ) ( )│
│        B   │           │            ││        B   │           │            │
│( ) ( )     │           │     ( ) ( )││( ) ( )     │           │     ( ) ( )│
│            └───────────┘            ││            └───────────┘            │
│( ) ( )                       ( ) ( )││( ) ( )                       ( ) ( )│
│                                     ││                                     │
│[ ] ( )  ┌────┐        LED4   [ ] ( )││[ ] ( )  ┌────┐        LED4   [ ] ( )│
│         │SW1 │                      ││         │SW1 │                      │
│         │    │                      ││( ) ( )  │    │               ( ) ( )│
│         └────┘                      ││         └────┘                      │
│            ││ ||||||| ││            ││( ) ( )     ││ ||||||| ││     ( ) ( )│
│          O               O          ││          O               O          │
│          │               │          ││          │               │          │
│  ───     │      USB      │    .───. ││  ───     │      USB      │    .───. │
. │   │    o               o    │   │ .. │   │    o               o    │   │ .
 \'───'    │               │    '───'/  \'───'    │               │    '───'/
  `─────────────────────────────────'    `─────────────────────────────────'

Signals to fit onto these headers in each corner of the board:

• Power rails: GND, 5V, 3V3, 1V2, 3V3_STBY (for FPGA ram standby when in "deep sleep" mode)
• Power signals: PWR_EN, PICO_ADC2_PB (push-button)
• I2C: SCL, SDA (common to ATtiny, RP2040, ICE40, Feather, StemmaQT, QWIIC...)

[josuah]

The PICO_ADC2_PB (push-button) is a soft button, connected to one Pico GPIO, as described by @z80 on the chat:

[josuah]

• The above diagram would go on the shield, but exhibit the ADC|PB and PWR_EN signals.
• The GPIO pin used for the ADC2|PB signal is GPIO28 of the Pico (ADC2)
• The ADC2 could be used as an ADC pin, to keep away from i.e. SCK if possible.
• There is room for an extra GND: 9 signals, 10 pins.

[josuah]

The pin placement of the shield headers was for giving it enough room for the shield content, while keeping the accessibility of the various buttons and LEDs on the board.

[josuah]

This would then be the layout of the shield:

┌───────┬─────────────────────┬───────┐
│( ) ( )│                     │( ) ( )│
├───────┘                     └───────┤
│                                     │
│                                     │
│                                     │
│                                     │
│                                     │
│                                     │
│                                     │
│                                     │
│                                     │
│                                     │
│                                     │
│                                     │
│                                     │
│                                     │
│                                     │
├───────┐                     ┌───────┤
│( ) ( )│                     │( ) ( )│
│       │                     │       │
│( ) ( )│                     │( ) ( )│
└───────┴─────────────────────┴───────┘

[vr2045]

Pinout has changed a bit, please see the latest schematic for the details.

[josuah]

USB pull up/down jumper resistor

In order to allow the USB to be used in host/peripheral mode, 56k Ohm pull-up/pull-down resistor is to be used. To allow customization without too much board space (switch, 2.54" jumpers, 2 extra solder jumper + extra resistor...), a resistor could be used as a jumper, by desoldering/resoldering it onto another position if needed:

  │           │
 +│5V   CC   G│ND
┌─┴──┐┌────┐┌─┴──┐
│    ││ ┌──────┐ │
│    ││ │ 5.1k │ │
│    ││ └──────┘ │
└────┘└─┬──┘└────┘
        │

[vr2045]

Good idea, added 2 way jumper with default as a peripheral.

[josuah]

Remove unneeded testpoints
Given the shield header interface provides all power rails, it could be possible to save some board space by removing the test points related to power rail.

[vr2045]

Done, removed 1.2V and 3.3V test points.