Neotron Pico 2 using the RP2350 Stamp XL

[thejpster]

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