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Diffstat (limited to 'ebus-racket/ebus/layer2.rkt')
| -rw-r--r-- | ebus-racket/ebus/layer2.rkt | 104 |
1 files changed, 104 insertions, 0 deletions
diff --git a/ebus-racket/ebus/layer2.rkt b/ebus-racket/ebus/layer2.rkt new file mode 100644 index 0000000..3dd881c --- /dev/null +++ b/ebus-racket/ebus/layer2.rkt @@ -0,0 +1,104 @@ +#lang racket/base +(require racket/bool + (planet bzlib/parseq:1:3)) + +(define logger (make-logger 'ebus-layer2 (current-logger))) +;; 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-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 (choice parse-ebus-mastermaster + parse-ebus-masterslave))) + (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)) + (log-message logger 'debug (format "drop ~s x SYN (~s)" syn ebus-const-syn) #t))) + (cond ((not (false? paket)) + paket) + ((eof-object? (peek-byte input-port)) + eof) + (else + ;; skip one byte + (let ([byte (read-byte input-port)]) + (log-message logger 'debug (format "drop ~s 0x~x ~n" byte byte) #t)) + (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)) + (prefix-out layer2- logger))
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