[Article] Star64 JH7110 + NuttX RTOS: RISC-V PLIC Interrupts and Serial I/O

[lupyuen]

Apache NuttX RTOS on Star64 JH7110 RISC-V SBC is almost ready! But we're stuck with 16550 UART Controller firing too many Spurious Interrupts.

In this article, we explain…
(1) Why there’s No Console Output from NuttX Apps
(2) How Serial I/O works in NuttX QEMU
(3) How UART I/O differs for Star64 vs QEMU
(4) What’s the RISC-V Platform-Level Interrupt Controller (PLIC)
(5) Why we delegate RISC-V Machine-Mode Interrupts to Supervisor-Mode
(6) How NuttX Star64 handles UART Interrupts
(7) Which leads to a new problem: 16550 UART Controller fires too many Spurious Interrupts!


Star64 JH7110 + NuttX RTOS: RISC-V PLIC Interrupts and Serial I/O