@startuml
scale max 900*520
skinparam backgroundColor transparent
skinparam shadowing false
skinparam defaultFontName "DejaVu Sans Mono"
skinparam defaultFontSize 13
skinparam ArrowColor #8295a0
skinparam classBorderColor #2b6f8e
skinparam classBackgroundColor #edf6fa
skinparam classFontColor #183f53
skinparam roundcorner 10
top to bottom direction
title A2 STRUCTURE — queue length 1 and three task contexts

class "01 QueueMessage" as Message {
  sequence : uint32_t
  payload : uint32_t
  checksum : uint32_t
}
class "02 Queue<1 × QueueMessage>" as Queue <<FreeRTOS object>> {
  uxLength = 1
  uxItemSize = 12
  waiting : List_t
}
class "03 receiver" as Receiver <<task p3>>
class "04 sender" as Sender <<task p2>>
class "05 verifier" as Verifier <<task p1>>
class "06 bounded evidence[12]" as Evidence

Sender -down-> Queue : xQueueSend copies bytes
Queue -down-> Receiver : xQueueReceive copies bytes
Receiver ..> Message
Sender ..> Message
Receiver --> Evidence : publish
Sender --> Evidence : publish
Verifier --> Evidence : digest
Verifier ..> Queue : verifies FIFO / states
@enduml