ucmb: Add more documentation and example code for AVR8
git-svn-id: svn://svn.openwrt.org/openwrt/packages@14564 3c298f89-4303-0410-b956-a3cf2f4a3e73
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mb
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@ -23,6 +23,19 @@ define KernelPackage/ucmb
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AUTOLOAD:=$(call AutoLoad,93,ucmb)
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endef
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define KernelPackage/ucmb/description
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The Microcontroller Message Bus is a tiny SPI-GPIO based communication
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channel used to talk to microcontrollers over GPIO pins.
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The lowlevel protocol is CRC16 protected, so one can be pretty sure
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that the data transmitted and received through the /dev/ucmb node is not corrupted.
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So no further checks should be needed at upper protocol layers.
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The device node considers every read/write to be one packet. The maximum packet
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size is either PAGE_SIZE (at least 4kb) or the microcontroller specific packet size
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limit, which is likely to be a lot smaller than PAGE_SIZE.
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Example implementations for the microcontroller-side code can be found in
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the utils/ucmb/microcontroller_examples subdirectory of the OpenWRT packages feed.
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endef
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define Build/Prepare
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mkdir -p $(PKG_BUILD_DIR)
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$(CP) ./driver/* $(PKG_BUILD_DIR)/
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@ -22,7 +22,7 @@
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#define PFX "ucmb: "
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#define DEBUG
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#undef DEBUG
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MODULE_LICENSE("GPL");
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@ -60,7 +60,6 @@ struct ucmb_status {
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} __attribute__((packed));
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#define UCMB_MAGIC 0x1337
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#define UCMB_MAX_MSG_LEN 0x200
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enum ucmb_status_code {
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UCMB_STAT_OK = 0,
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@ -217,7 +216,6 @@ static ssize_t ucmb_write(struct file *filp, const char __user *user_buf,
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goto out;
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size = min_t(size_t, PAGE_SIZE, size);
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size = min_t(size_t, UCMB_MAX_MSG_LEN, size);
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err = -EFAULT;
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if (copy_from_user(buf, user_buf, size))
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goto out_free;
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213
utils/ucmb/microcontroller_examples/atmel_avr8/ucmb.c
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213
utils/ucmb/microcontroller_examples/atmel_avr8/ucmb.c
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@ -0,0 +1,213 @@
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/*
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* Microcontroller message bus
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* uc-side slave implementation for Atmel AVR8
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*
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* The gcc compiler always treats multi-byte variables as litte-endian.
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* So no explicit endianness conversions are done on the message header,
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* footer and status data structures.
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*
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* Copyright (C) 2009 Michael Buesch <mb@bu3sch.de>
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version 2
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* of the License, or (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*/
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#include "ucmb.h"
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#include <stdint.h>
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#include <avr/io.h>
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#include <avr/interrupt.h>
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#include <util/crc16.h>
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struct ucmb_message_hdr {
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uint16_t magic; /* UCMB_MAGIC */
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uint16_t len; /* Payload length (excluding header) */
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} __attribute__((packed));
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struct ucmb_message_footer {
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uint16_t crc; /* CRC of the header + payload. */
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} __attribute__((packed));
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struct ucmb_status {
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uint16_t magic; /* UCMB_MAGIC */
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uint16_t code; /* enum ucmb_status_code */
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} __attribute__((packed));
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#define UCMB_MAGIC 0x1337
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enum ucmb_status_code {
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UCMB_STAT_OK = 0,
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UCMB_STAT_EPROTO, /* Protocol format error */
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UCMB_STAT_ENOMEM, /* Out of memory */
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UCMB_STAT_E2BIG, /* Message too big */
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UCMB_STAT_ECRC, /* CRC error */
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};
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static uint8_t ucmb_buf[sizeof(struct ucmb_message_hdr) +
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UCMB_MAX_MSG_LEN +
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sizeof(struct ucmb_message_footer)];
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static uint16_t ucmb_buf_ptr;
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static struct ucmb_status status_buf;
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static uint16_t ucmb_send_message_len;
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/* Statemachine */
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static uint8_t ucmb_state;
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enum {
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UCMB_ST_LISTEN,
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UCMB_ST_SENDSTATUS,
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UCMB_ST_SENDMESSAGE,
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};
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#define TRAILING 1
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static void ucmb_send_next_byte(void)
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{
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switch (ucmb_state) {
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case UCMB_ST_SENDSTATUS: {
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const uint8_t *st = (const uint8_t *)&status_buf;
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if (ucmb_buf_ptr < sizeof(struct ucmb_status))
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SPDR = st[ucmb_buf_ptr];
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ucmb_buf_ptr++;
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if (ucmb_buf_ptr == sizeof(struct ucmb_status) + TRAILING) {
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ucmb_buf_ptr = 0;
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if (ucmb_send_message_len) {
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ucmb_state = UCMB_ST_SENDMESSAGE;
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goto st_sendmessage;
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} else
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ucmb_state = UCMB_ST_LISTEN;
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}
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break;
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}
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case UCMB_ST_SENDMESSAGE: {
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st_sendmessage:;
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uint16_t full_length = sizeof(struct ucmb_message_hdr) +
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ucmb_send_message_len +
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sizeof(struct ucmb_message_footer);
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if (ucmb_buf_ptr < full_length)
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SPDR = ucmb_buf[ucmb_buf_ptr];
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ucmb_buf_ptr++;
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if (ucmb_buf_ptr == full_length + TRAILING) {
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ucmb_send_message_len = 0;
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ucmb_buf_ptr = 0;
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ucmb_state = UCMB_ST_LISTEN;//FIXME retr status
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}
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break;
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} }
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}
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static uint16_t crc16_block_update(uint16_t crc, const void *_data, uint16_t size)
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{
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const uint8_t *data = _data;
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while (size) {
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crc = _crc16_update(crc, *data);
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data++;
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size--;
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}
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return crc;
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}
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static uint16_t ucmb_calc_msg_buffer_crc(void)
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{
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const struct ucmb_message_hdr *hdr;
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uint16_t crc = 0xFFFF;
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hdr = (const struct ucmb_message_hdr *)ucmb_buf;
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crc = crc16_block_update(crc, ucmb_buf,
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sizeof(struct ucmb_message_hdr) + hdr->len);
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crc ^= 0xFFFF;
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return crc;
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}
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/* SPI data transfer interrupt. */
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ISR(SPI_STC_vect)
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{
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uint8_t data;
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data = SPDR;
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switch (ucmb_state) {
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case UCMB_ST_LISTEN: {
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struct ucmb_message_hdr *hdr;
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struct ucmb_message_footer *footer;
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ucmb_buf[ucmb_buf_ptr++] = data;
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if (ucmb_buf_ptr < sizeof(struct ucmb_message_hdr))
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return; /* Header RX not complete. */
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hdr = (struct ucmb_message_hdr *)ucmb_buf;
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if (ucmb_buf_ptr == sizeof(struct ucmb_message_hdr)) {
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if (hdr->magic != UCMB_MAGIC) {
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/* Invalid magic! Reset. */
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ucmb_buf_ptr = 0;
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return;
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}
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if (hdr->len > UCMB_MAX_MSG_LEN) {
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/* Invalid length. */
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//FIXME don't interrupt, but poll len bytes and
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// send an immediate failure report
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ucmb_buf_ptr = 0;
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return;
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}
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return;
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}
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if (ucmb_buf_ptr == sizeof(struct ucmb_message_hdr) +
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sizeof(struct ucmb_message_footer) +
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hdr->len) {
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footer = (struct ucmb_message_footer *)(
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ucmb_buf + sizeof(struct ucmb_message_hdr) +
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hdr->len);
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status_buf.magic = UCMB_MAGIC;
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status_buf.code = UCMB_STAT_OK;
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if (ucmb_calc_msg_buffer_crc() != footer->crc)
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status_buf.code = UCMB_STAT_ECRC;
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ucmb_state = UCMB_ST_SENDSTATUS;
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ucmb_buf_ptr = 0;
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ucmb_send_next_byte();
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ucmb_send_message_len = ucmb_rx_message(
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ucmb_buf + sizeof(struct ucmb_message_hdr),
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hdr->len);
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if (ucmb_send_message_len) {
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footer = (struct ucmb_message_footer *)(
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ucmb_buf + sizeof(struct ucmb_message_hdr) +
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ucmb_send_message_len);
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hdr->magic = UCMB_MAGIC;
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hdr->len = ucmb_send_message_len;
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footer->crc = ucmb_calc_msg_buffer_crc();
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}
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}
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break;
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}
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case UCMB_ST_SENDSTATUS:
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case UCMB_ST_SENDMESSAGE:
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ucmb_send_next_byte();
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break;
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}
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}
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void ucmb_init(void)
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{
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ucmb_state = UCMB_ST_LISTEN;
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/* SPI slave mode 0 with IRQ enabled. */
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DDRB |= (1 << 4/*MISO*/);
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DDRB &= ~((1 << 5/*SCK*/) | (1 << 3/*MOSI*/) | (1 << 2/*SS*/));
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SPCR = (1 << SPE) | (1 << SPIE) /*| (1 << CPOL) | (1 << CPHA)*/;
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(void)SPSR; /* clear state */
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(void)SPDR; /* clear state */
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}
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24
utils/ucmb/microcontroller_examples/atmel_avr8/ucmb.h
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24
utils/ucmb/microcontroller_examples/atmel_avr8/ucmb.h
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@ -0,0 +1,24 @@
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#ifndef UCMB_AVR8_H_
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#define UCMB_AVR8_H_
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#include <stdint.h>
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/* Max length of the message payload. */
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#define UCMB_MAX_MSG_LEN 0x200
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/* ucmb_rx_message - Message receive callback.
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* Define this elsewhere. It's called on successful retrieval
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* of a new message.
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* If a reply message has to be transferred after this one, put the
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* message payload into the "payload" buffer and return the number
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* of bytes to transmit. If no reply message is needed, return 0.
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* Note that the "payload" buffer always has a size of UCMB_MAX_MSG_LEN.
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*/
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extern uint16_t ucmb_rx_message(uint8_t *payload,
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uint16_t payload_length);
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/* Initialize the UCMB subsystem. */
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void ucmb_init(void);
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#endif /* UCMB_AVR8_H_ */
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