Neotron-Compute/Neotron-Pico
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CLI
GitHub Desktop
Neotron
ATX
PIO
SPI
SD Card
Slot 1'
the Board Management Controller
Slot 0'
Slot 2'
Slot 7'
IRQ
the Neotron OS
CP/M
Microchip MCP23S17 SPI
GPIO
VGA
TPD7S019
DVI
HDMI
Reset
UART
Data Terminal Equipment
IBM
Intel
ISA
AT24C256
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GND
AT24C256 EEPROM
TE
PCI
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Creative Commons Attribution
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Neotron
Raspberry Pi Pico
Use Git
Instuments Tiva-C Launchpad
THS7316
Chip Select
MCP23S17
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Physical locations
Neotron-32
Pico
Places
the Raspberry Pi Pico
the Neotron Pico
the Pico for Audio and Video
Locations
Texas
SD
8-bit
Events
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Summary
The eight chip-selects are gated with a tri-state bus transceiver, allowing the Pico to talk to either the I/O exander, or the selected expansion slot. Each expansion slot has both I²C and SPI, along with unique chip-select and IRQ signals.The Neotron Pico is designed to run the Neotron OS - a CP/M or MS-DOS alike OS written in Rust. Each device we wish to communicate with on the SPI bus must have a unique chip select line and so have limited lines means we could only have a limited number of SPI devices.However, in this design, we cheat and use a Microchip MCP23S17 I/O expander. It also has an IRQ output which be programmed to fire when the input pins match a certain state.The problem would come when the Pico has finished talking to our select SPI device - how does it tell the MCP23S17 to release the current chip select, without the SPI bus traffic also going to the currently selected expansion slot?
As said here by Neotron-Compute