BlackMark
a977e507f3
Clock, baud, serial backend (hardware USART 0/1 or the software UART on any pins) and the activation window all resolve through one CMake function, pureboot_add_loader() in pureboot/CMakeLists.txt — the unit a downstream project consumes. The default baud is the fastest standard rate within 2.5 % (the same best-divisor search libavr's solver runs), gated on software builds by the polled receiver's 100-cycles-a-bit floor; every explicit pick is re-checked by the compile's static asserts. The size matrix builds each axis that can move the image — backend x clock ladder x USART instance, per chip — against the slot budget, and two nondefault deployments run the whole protocol suite live: the 328P on its shipped 1 MHz fuses over software serial on TX=PB1/RX=PB5 (pureboot.custom), and the 644A over USART1 (pureboot.usart1). The sim runner takes -l to bridge any link, paces a fully quiet bridge toward real time (a free-running 8 M-cycle window loses the reset-race knock), and the fixture application speaks the deployment it is built for. The loader itself shed bytes on the way: the return-address high byte spelled through byteswap (the double swap folds to the one-byte pick), the info-block address composed instead of bit_cast, and libavr's new polled-UART helpers replacing the port's uart::detail reaches. Every combination fits: 458-506 B across the megas' whole matrix, 470-484 B on the tinies, 556-562 B in the 1284s' 1 KiB slot. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
107 lines
3.0 KiB
C++
107 lines
3.0 KiB
C++
// Test-fixture application for the pureboot protocol tests: prints "APP" on
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// the chip's serial link (the same link the loader uses) — the proof that
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// the loader's hand-over, and on the tinies the host's reset-vector
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// surgery, actually launched it. Linked normally (crt, vectors at 0); on
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// the tinies its reset vector is the rjmp the host re-homes.
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//
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// On the hardware-USART link it then listens, and an 'L' makes it jump into
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// the resident loader — the application-owned loader entry a
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// BOOTRST-unprogrammed mega relies on (reset always boots the application
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// there), exercised by the self-update tests. The software link idles:
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// reset reaches those loaders through the patched vector (or the runner
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// models BOOTRST), so the application owes them nothing.
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//
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// The fixture speaks the deployment its loader was built for: the same
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// PUREBOOT_* defines configure it, and without them it assumes the stock
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// deployment (the crystal/RC clock table below, the chip's natural link).
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#include <libavr/libavr.hpp>
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using namespace avr::literals;
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namespace {
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consteval avr::hertz_t clock()
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{
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#if defined(PUREBOOT_CLOCK_HZ)
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return avr::hertz_t{PUREBOOT_CLOCK_HZ};
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#else
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auto name = std::string_view{avr::hw::db.name};
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if (name.starts_with("ATtiny13"))
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return 9.6_MHz;
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if (name.starts_with("ATtiny"))
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return 8_MHz;
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return 16_MHz;
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#endif
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}
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#if !defined(PUREBOOT_TX)
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#define PUREBOOT_TX pb1
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#endif
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#if !defined(PUREBOOT_USART)
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#define PUREBOOT_USART 0
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#endif
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consteval bool use_hardware()
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{
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#if defined(PUREBOOT_SOFT_SERIAL)
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return false;
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#else
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return avr::hw::db.has_instance("USART0") || avr::hw::db.has_instance("USART");
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#endif
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}
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using dev = avr::device<{.clock = clock()}>;
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template <avr::hertz_t C, bool Hardware = use_hardware()>
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struct link {
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#if defined(PUREBOOT_BAUD)
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static constexpr avr::baud_t baud{PUREBOOT_BAUD};
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#else
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static constexpr avr::baud_t baud{115200};
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#endif
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using tx_t = avr::uart::usart<'0' + PUREBOOT_USART, C, {.baud = baud, .max_baud_error = 2.5_pct}>;
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static void tx(char c)
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{
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tx_t::write(static_cast<std::uint8_t>(c));
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}
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[[noreturn]] static void idle()
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{
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// 'L' hands back to the loader at the top slot — 512 bytes, or the
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// 1 KiB the >64 KiB chips use.
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constexpr std::uint32_t slot = avr::hw::db.mem.flash_size > 65536 ? 1024 : 512;
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for (;;)
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if (tx_t::read_blocking() == 'L')
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reinterpret_cast<void (*)()>(static_cast<std::uint16_t>((avr::hw::db.mem.flash_size - slot) / 2))();
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}
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};
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template <avr::hertz_t C>
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struct link<C, false> {
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#if defined(PUREBOOT_BAUD)
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static constexpr avr::baud_t baud{PUREBOOT_BAUD};
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#else
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static constexpr avr::baud_t baud{57600};
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#endif
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using tx_t = avr::uart::software_tx<C, avr::PUREBOOT_TX, baud>;
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static void tx(char c)
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{
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tx_t::write(static_cast<std::uint8_t>(c));
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}
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[[noreturn]] static void idle()
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{
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while (true) {
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}
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}
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};
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} // namespace
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int main()
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{
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avr::init<typename link<dev::clock>::tx_t>();
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link<dev::clock>::tx('A');
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link<dev::clock>::tx('P');
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link<dev::clock>::tx('P');
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link<dev::clock>::idle();
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}
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