root / trunk / code / projects / i2c_charge_station / i2c_auto.c @ 1862
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| 1 | 666 | kwoo | /**
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| 2 | * This is the API for i2c_autodetect used on the
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| 3 | * charging station. This block explains the high
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| 4 | * level implementation. The functions below explain
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| 5 | * the low level.
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| 6 | *
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| 7 | ***** High Level *****
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| 8 | * Since the charge stations are hooked up
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| 9 | * via i2c lines, we must determine one master. We
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| 10 | * decide that the one with the XBee is the master.
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| 11 | * There should only be one Xbee in an i2c chain, though
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| 12 | * in the case that there are two, the second one to detect
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| 13 | * that they have an XBee must yeild the the older one.
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| 14 | * All others are slaves. At startup, we check if we have an
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| 15 | * XBee. If so, we poll for master, if there is none we declare
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| 16 | * ourselves master. If you do not have an XBee, poll the line
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| 17 | * asking for a master. If there is none, wait for a while and
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| 18 | * then try again until the master assigns you an ID.
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| 19 | * Once you have an ID, wait until the Master sends you commands.
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| 20 | * Periodically check if you have an XBee, just in case.
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| 21 | * The master must hand out IDs to the slaves. These IDs are
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| 22 | * kept in a table that indicates the status of the station.
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| 23 | * Occassionally poll the slaves to make sure they are not there and
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| 24 | * update the table as needed. If a packet comes in over XBee,
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| 25 | * forward to the correct charging station.
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| 26 | * In the event that the master loses the XBee, broadcast a message
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| 27 | * indicating that. Then poll for a new master. When one comes on,
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| 28 | * pass it the table.
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| 29 | **/
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| 30 | |||
| 31 | /**
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| 32 | * Sets up the needed states for i2c_autodetect
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| 33 | */
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| 34 | void i2c_startup (void) { |
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| 35 | |||
| 36 | } |
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| 37 | |||
| 38 | /**
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| 39 | * Checks if an XBee is present.
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| 40 | *
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| 41 | * @return 0 if false, 1 if true
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| 42 | */
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| 43 | char i2c_has_xbee(void) { |
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| 44 | |||
| 45 | } |
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| 46 | |||
| 47 | /**
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| 48 | * Acting as a temporary master, poll the master for an ID. If there
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| 49 | * is a master, he should respond with an ID in which case you should
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| 50 | * add that as your ID. Otherwise leave your ID blank.
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| 51 | *
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| 52 | * @return your ID, otherwise 0x00
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| 53 | */
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| 54 | char i2c_request_id(void) { |
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| 55 | |||
| 56 | } |
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| 57 | |||
| 58 | /**
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| 59 | * This should be called on the reception of an ID request. Since this
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| 60 | * will be called during an interrupt, make it as fast as possible.
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| 61 | * Check for the next available ID in the allocation table ans assign it.
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| 62 | * Send the ID back on the bus.
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| 63 | **/
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| 64 | void i2c_allocate_id(void) { |
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| 65 | |||
| 66 | } |
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| 67 | |||
| 68 | /**
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| 69 | * This is your handler function to be called by the i2c interrupt. You
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| 70 | * should get only 1 byte at a time and it will not be buffered. Handle it
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| 71 | * fast. You should analyze if the packet is a ID request, a poll, a transfer
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| 72 | * ID table, or data and then call the correct function. Basically this is a
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| 73 | * giant switch.
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| 74 | *
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| 75 | * @param data Data byte received from master
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| 76 | */
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| 77 | void i2c_receive_data(char data) { |
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| 78 | |||
| 79 | } |
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| 80 | |||
| 81 | /**
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| 82 | * Called if a poll request has been received. Since this is in an interrupt make it
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| 83 | * fast. Queues up a poll response message to the master.
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| 84 | */
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| 85 | void i2c_poll_respond(void) { |
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| 86 | |||
| 87 | } |
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| 88 | |||
| 89 | /**
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| 90 | * This should be done periodically. The allocation table should have a time since
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| 91 | * last poll field which counts down along with a poll send bit.
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| 92 | * If time reaches 0 after a poll remove it. This function, when
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| 93 | * called with a NULL should run through the table and send out request to all
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| 94 | * those who are not currently being polled and check if those who have polls
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| 95 | * have reached 0 and remove them. If called with an ID, set the poll status
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| 96 | * bit for that ID to 0.
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| 97 | *
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| 98 | * @param ID ID of the slave who has responded. If NULL poll all those not being polled
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| 99 | */
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| 100 | void i2c_poll_slaves_send(char ID) { |
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| 101 | |||
| 102 | } |
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| 103 | |||
| 104 | /**
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| 105 | * Call this if you have lost the XBee and a new master has arrived. You should
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| 106 | * transfer the entire table over to the new master.
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| 107 | */
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| 108 | void i2c_transfer_table(void) { |
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| 109 | |||
| 110 | } |
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| 111 | |||
| 112 | /**
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| 113 | * Call this if you receive a transfer table request. You should accept it and
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| 114 | * merge it into your table.
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| 115 | */
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| 116 | void i2c_receive_table(void) { |
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| 117 | |||
| 118 | } |
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| 119 |