Neotron Pico 2 using the RP2350 Stamp XL #186
Description
The RP2350B (available on the RP2350 Stamp XL) has 16 extra pins - 48 to be exact. This is enough to add HDMI output (eight pins) and a full set of IRQ and CS pins (16 in total). By controlling the CS/IRQ pins directly we can remove the MCP23S17 and the 74HC138 and we improve performance when changing devices on the bus. You could also drop down to six slots instead of eight slots, and free up four pins for debug LEDs. Or something like direct PS/2 keyboard/mouse support.
We could use a DVI-I connector because it carries both TMDS digital video and analog RGB video - cheap adapters to either VGA or HDMI are available, and it would save space on the board edge for the USB ports.
Raw access to the dedicated USB D+/D- pins also means we can fit an on-board USB Hub, like a TI TUSB2046.
Proposed pinout for the Stamp XL:
| GPIO | Function |
|---|---|
| 0 | IRQ0 |
| 1 | IRQ1 |
| 2 | IRQ2 |
| 3 | IRQ3 |
| 4 | IRQ4 |
| 5 | IRQ5 |
| 6 | IRQ6 |
| 7 | IRQ7 |
| 8 | QSPI1_IRQ (for PSRAM) |
| 9 | CS0 |
| 10 | CS1 |
| 11 | CS2 |
| 12 | HSTX0 |
| 13 | HSTX1 |
| 14 | HSTX2 |
| 15 | HSTX3 |
| 16 | HSTX4 |
| 17 | HSTX5 |
| 18 | HSTX6 |
| 19 | HSTX7 |
| 20 | SPI0_RX |
| 21 | I2C0_SCL |
| 22 | SPI0_SCK |
| 23 | SPI0_TX |
| 24 | I2C0_SDA |
| 25 | I2S_BCLK |
| 26 | I2S_LRCLK |
| 27 | I2S_DIN |
| 28 | I2S_DOUT |
| 29 | CS3 |
| 30 | CS4 |
| 31 | CS5 |
| 32 | CS6 |
| 33 | CS7 |
| 34 | HSYNC |
| 35 | VSYNC |
| 36 | RED0 |
| 37 | RED1 |
| 38 | RED2 |
| 39 | RED3 |
| 40 | GREEN0 |
| 41 | GREEN1 |
| 42 | GREEN2 |
| 43 | GREEN3 |
| 44 | BLUE0 |
| 45 | BLUE1 |
| 46 | BLUE2 |
| 47 | BLUE3 |
This is a workable pinout for the RP2350 Stamp. It has HDMI but no VGA, only supports six slots, and has no CS pin for PSRAM (because the RP2350 Stamp doesn't have pads for a PSRAM). As the RP2350 Stamp and the RP2350 Stamp XL are the same price, this doesn't really save us anything except space - which we are not short on.
| GPIO | Function |
|---|---|
| 0 | IRQ0 |
| 1 | IRQ1 |
| 2 | IRQ2 |
| 3 | IRQ3 |
| 4 | IRQ4 |
| 5 | IRQ5 |
| 6 | CS0 |
| 7 | CS1 |
| 8 | CS2 |
| 9 | CS3 |
| 10 | CS4 |
| 11 | CS5 |
| 12 | HSTX0 |
| 13 | HSTX1 |
| 14 | HSTX2 |
| 15 | HSTX3 |
| 16 | HSTX4 |
| 17 | HSTX5 |
| 18 | HSTX6 |
| 19 | HSTX7 |
| 20 | SPI0_RX |
| 21 | I2C0_SCL |
| 22 | SPI0_SCK |
| 23 | SPI0_TX |
| 24 | I2C0_SDA |
| 25 | I2S BCLK |
| 26 | I2S LRCLK |
| 27 | I2S DIN |
| 28 | I2S DOUT |
| 29 | Spare |