https://dean.sellers.id.au/tags/pwm/ Recent content in Pwm on Ampsand Hugo en-AU Dean Sellers Thu, 29 Oct 2026 12:04:08 +1100 https://dean.sellers.id.au/2026/10/19/riscv-12-larson-again/ Mon, 19 Oct 2026 01:00:00 +1100 https://dean.sellers.id.au/2026/10/19/riscv-12-larson-again/ <p class="post-subtitle">The scanner, third time</p><p><em>Part 12 of the RISC-V soft core series. Previously: <a href="https://dean.sellers.id.au/2026/10/19/riscv-11-where-it-breaks/">Where it breaks</a>.</em></p> <p>The Larson scanner has been the series&rsquo; test program from the start, and this is its third appearance.</p> <p>In <a href="https://dean.sellers.id.au/2026/10/18/riscv-01-a-cpu-you-can-watch/">part 1</a> it was the blinkenlights: eight LEDs, one bit shifted along in assembly, and the only thing worth looking at was the CPU going FETCH, EXECUTE, FETCH. In <a href="https://dean.sellers.id.au/2026/10/19/riscv-06-time-and-interrupts/">parts 6</a> and <a href="https://dean.sellers.id.au/2026/10/19/riscv-08-sleeping/">8</a> it climbed the timing ladder: a delay loop, a polled deadline, then a timer interrupt with the CPU asleep in <code>wfi</code> between steps. The CPU stopped being the busy part.</p>