avr/bootloader
1
0
Fork 0
Code Issues Pull Requests Releases Wiki Activity

test: the exhaustive clock x baud x backend size matrix

Browse Source 
Every plausible oscillator against every rate it reaches against every
backend, on one chip per size-bearing class, under --full only. The baud
ladder becomes a reachability predicate the enumeration filters on, so an
unreachable point drops out instead of aborting the configure.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
This commit is contained in:
BlackMark
2026-07-22 23:32:28 +02:00
parent 8f106b636d
commit a5b42bc02f
4 changed files with 123 additions and 55 deletions
Download Patch File Download Diff File Expand all files Collapse all files

63
pureboot/CMakeLists.txt
View File

@@ -146,36 +146,51 @@ set(PUREBOOT_HAS_USART ${_pb_has_usart} PARENT_SCOPE)
set(PUREBOOT_HAS_USART1 ${_pb_has_usart1} PARENT_SCOPE)
set(PUREBOOT_SIM_MCU ${_pb_sim_mcu} PARENT_SCOPE)
# The fastest standard rate the clock reaches within 2.5 %, by the same
# best-of-U2X-and-plain divisor search libavr's solve_baud runs, so a default
# The rates a default may pick, fastest first.
set_property(GLOBAL PROPERTY PUREBOOT_BAUD_LADDER 115200 57600 38400 19200 9600)
# Whether <baud> is reachable from <clock> within 2.5 %, by the same
# best-of-U2X-and-plain divisor search libavr's solve_baud runs, so a build
# never trips the compile-time error it is checked against. A software build
# also needs the polled receiver's 100-cycles-a-bit floor: at low clocks the
# U2X divisor reaches rates the bit-banged sampler cannot.
function(pureboot_default_baud clock software outvar)
foreach(baud 115200 57600 38400 19200 9600)
math(EXPR _cycles "${clock} / ${baud}")
if(software AND _cycles LESS 100)
function(pureboot_baud_feasible clock baud software outvar)
set(${outvar} 0 PARENT_SCOPE)
math(EXPR _cycles "${clock} / ${baud}")
if(software AND _cycles LESS 100)
return()
endif()
foreach(divisor 8 16)
math(EXPR _step "${divisor} * ${baud}")
math(EXPR _n "(${clock} + ${_step} / 2) / ${_step}")
if(_n LESS 1 OR _n GREATER 4096)
continue()
endif()
foreach(divisor 8 16)
math(EXPR _step "${divisor} * ${baud}")
math(EXPR _n "(${clock} + ${_step} / 2) / ${_step}")
if(_n LESS 1 OR _n GREATER 4096)
continue()
endif()
math(EXPR _actual "${clock} / (${divisor} * ${_n})")
math(EXPR _delta "${_actual} - ${baud}")
if(_delta LESS 0)
math(EXPR _delta "-(${_delta})")
endif()
math(EXPR _error_bp "${_delta} * 10000 / ${baud}")
if(_error_bp LESS_EQUAL 250)
set(${outvar} ${baud} PARENT_SCOPE)
return()
endif()
endforeach()
math(EXPR _actual "${clock} / (${divisor} * ${_n})")
math(EXPR _delta "${_actual} - ${baud}")
if(_delta LESS 0)
math(EXPR _delta "-(${_delta})")
endif()
math(EXPR _error_bp "${_delta} * 10000 / ${baud}")
if(_error_bp LESS_EQUAL 250)
set(${outvar} 1 PARENT_SCOPE)
return()
endif()
endforeach()
message(FATAL_ERROR "pureboot: no standard baud rate fits a ${clock} Hz clock within 2.5 %")
endfunction()
# The fastest ladder rate the clock reaches.
function(pureboot_default_baud clock software outvar)
get_property(_ladder GLOBAL PROPERTY PUREBOOT_BAUD_LADDER)
foreach(baud ${_ladder})
pureboot_baud_feasible(${clock} ${baud} ${software} _ok)
if(_ok)
set(${outvar} ${baud} PARENT_SCOPE)
return()
endif()
endforeach()
message(FATAL_ERROR "pureboot: no standard baud rate fits a ${clock} Hz clock within 2.5 % "
"— pass BAUD <rate> to deploy a non-standard one")
endfunction()
# pureboot_add_loader(<name> [CLOCK <hz>] [BAUD <bd>]