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#lang racket/base
(require racket/bool
(planet bzlib/parseq:1:3))
;; Ebus SYN
(define ebus-const-syn #xaa)
;; Ebus Escape-Sequence Start
(define ebus-const-escape #xa9)
;; Ebus ACK
(define ebus-const-ackok #x00)
;; Ebus Broadcast Address
(define ebus-const-broadcastaddr 254)
(struct ebus-body-broadcast (crc) #:transparent)
(struct ebus-body-mastermaster (crc) #:transparent)
(struct ebus-body-masterslave
(crc payloadSlaveLength payloadSlave crcSlave)
#:transparent)
(struct ebus-paket
(source destination primaryCommand secondaryCommand payloadLength payload body)
#:transparent)
;; single, maybe escaped, payload data byte
(define ebus-payload
(choice (seq escape-seq <- ebus-const-escape
escape-code <- (byte-in (list 0 1))
(return (cond
((= escape-code 0) ebus-const-escape)
((= escape-code 1) bytes ebus-const-syn))))
any-byte
))
(define parse-ebus-broadcast
(token (seq crc <- any-byte
syn <- ebus-const-syn
(return (ebus-body-broadcast crc)))))
(define parse-ebus-mastermaster
(token (seq crc <- any-byte
ack <- ebus-const-ackok ;; ACK des Empfängers
syn <- ebus-const-syn ;; SYN des Senders
(return (ebus-body-mastermaster crc)))))
(define parse-ebus-masterslave
(token (seq crc <- any-byte
ack <- ebus-const-ackok ;; ACK des Empfängers
payloadSlaveLength <- any-byte
payloadSlave <- (repeat ebus-payload payloadSlaveLength payloadSlaveLength)
crcSlave <- any-byte
ackSlave <- ebus-const-ackok ;; ACK des Senders
synSlave <- ebus-const-syn ;; SYN des Senders
(return (ebus-body-masterslave crc payloadSlaveLength payloadSlave crcSlave)))))
(define parse-ebus-master-or-slave (token (choice parse-ebus-mastermaster parse-ebus-masterslave)))
(define parse-ebus-paket
(token (seq source <- any-byte
destination <- any-byte
primaryCommand <- any-byte
secondaryCommand <- any-byte
payloadLength <- any-byte
payload <- (repeat ebus-payload payloadLength payloadLength)
body <- (cond ((= destination ebus-const-broadcastaddr) parse-ebus-broadcast)
(else parse-ebus-master-or-slave))
(return (ebus-paket source
destination
primaryCommand
secondaryCommand
payloadLength
payload
body)))))
(define ebus-sync (tokens syncs <- (seq (repeat (string->bytes/latin-1 "\xaa")))
(return (length syncs))))
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
(define (read-ebus input-port)
(define syn ((make-reader ebus-sync #:sof? #f #:eof? #f) input-port))
(define paket ((make-reader parse-ebus-paket #:sof? #f #:eof? #f) input-port))
(cond ((not (false? syn))
(display (format "drop ~s x SYN (~s) ~n" syn ebus-const-syn))))
(cond ((not (false? paket))
paket)
((eof-object? (peek-byte input-port))
eof)
(else
(let ([byte (read-byte input-port)])
(display (format "drop ~s 0x~x ~n" byte byte)))
;; skip one byte
(read-byte input-port)
(read-ebus input-port))))
(provide
;; Read Layer Ebus-Paket `ebus-paket`
(prefix-out layer2- read-ebus)
(prefix-out layer2- (struct-out ebus-paket))
(prefix-out layer2- (struct-out ebus-body-broadcast))
(prefix-out layer2- (struct-out ebus-body-mastermaster))
(prefix-out layer2- (struct-out ebus-body-masterslave)))
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