Serial Wombat
a general-purpose digital interface
device for hobbyists, engineers and students
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Serial Wombat Public data sources
Each pin provides a 16 bit value which can be seen by other pins and the host. The meaning of this piece of public data is dependent on the mode a pin is configured for. The public data index for each pin is its pin number.
Public data can be read by the host using the 'A' command.
Public data provided by one pin is frequently used by another. For example, in hysteresis control, one pin provides the input which controls a second pin configured for hysteresis output.
Additional system parameters are available as 16 bit public data under other indexes.
| Public Data Index | Meaning | |
| 0 | Public data index 0 always is 0 | |
| 1 through 40 | The public data provided by pins 1 through 40 | |
| 233 | The 8 bit value of port B, as defined in the 18F4620 datasheet. This 8 bit value represents the digital status of pins 33(least significant bit),34,35,36,37,38,39, and 40(most significant bit). This data is primarily designed to be used with the datalogger pin mode. Together, data 233, 234, 235, and 236 can be used with a datalogging pin to queue the state of 32 of the Wombat's pins at regular intervals. Note that pins which are configured as analog inputs will not also function as digital inputs with regard to this public data. | |
| 234 | The 8 bit value of port D, as defined in the 18F4620 datasheet. This 8 bit value represents the digital status of pins 19(least significant bit),20, 21, 22, 27, 28, 29 and 30(most significant bit). This data is primarily designed to be used with the datalogger pin mode. Together, data 233, 234, 235, and 236 can be used with a datalogging pin to queue the state of 32 of the Wombat's pins at regular intervals. | |
| 235 | The 8 bit value of port C, as defined in the 18F4620 datasheet. This 8 bit value represents the digital status of pins 15 (least significant bit),16, 17, 18, 23, 24, 25 and 26(most significant bit). This data is primarily designed to be used with the datalogger pin mode. Together, data 233, 234, 235, and 236 can be used with a datalogging pin to queue the state of 32 of the Wombat's pins at regular intervals. | |
| 236 | The 8 bit value of port A, as defined in the 18F4620 datasheet. This 8 bit value represents the digital status of pins 2 (least significant bit), 3, 4, 5, 6, 7, 14 and 13 (most significant bit; not a typo-they're out of order). This data is primarily designed to be used with the datalogger pin mode. Together, data 233, 234, 235, and 236 can be used with a datalogging pin to queue the state of 32 of the Wombat's pins at regular intervals. Note that pins which are configured as analog inputs will not also function as digital inputs with regard to this public data. | |
| 237 | Last Queue Accessed has been overflowed. After a queue is accessed (either by a pin mode or a host) the 237 public data will be a 1 if push-in attempts on this queue have been attempted while it was full. Accessing this public data will reset this flag to zero. It is not recommended to use this public data if more than one queue is active in the system, as the last queue accessed may vary depending on which pin was most recently accessing a queue. This data is intended to be used with the pulse mode during debugging to allow a visual or audio queue on queue overflow. | |
| 238 | Last Queue Accessed has been underflowed. After a queue is accessed (either by a pin mode or a host) the 238 public data will be a 1 if shift-out attempts on this queue have been attempted while it was empty. Accessing this public data will reset this flag to zero. It is not recommended to use this public data if more than one queue is active in the system, as the last queue accessed may vary depending on which pin was most recently accessing a queue. This data is intended to be used with the pulse mode during debugging to allow a visual or audio queue on queue underflow. | |
| 239 | Incrementing 16-bit number. This public data will increment each time it is accessed from any source (pin modes or requested by the host). It's primarily designed for testing. It will roll over from 65535 to 0. | |
| 245 | TX bytes sent This value increments each time a byte is sent to the host. It rolls over from 65535 to 0. |
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| 246 | RX byte received This value increments each time a byte is received from the host. It rolls over from 65535 to 0. |
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| 247 | Clock days This value increments once every 24 hours. The internal oscillator used to clock the Serial Wombat can be off by up to 1% and can vary with voltage and temperature, so this value should not be used for exact timing. |
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| 248 | Clock hours This value increments once every 60 minutes and rolls over from 23 to 0. The internal oscillator used to clock the Serial Wombat can be off by up to 1% and can vary with voltage and temperature, so this value should not be used for exact timing. |
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| 249 | Clock minutes This value increments once every 60 seconds and rolls over from 59 to 0. The internal oscillator used to clock the Serial Wombat can be off by up to 1% and can vary with voltage and temperature, so this value should not be used for exact timing. |
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| 250 | Clock seconds This value increments once per second and rolls over from 59 to 0. The internal oscillator used to clock the Serial Wombat can be off by up to 1% and can vary with voltage and temperature, so this value should not be used for exact timing. |
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| 251 | Receive Byte Overflows If the Wombat is heavily loaded and messages are sent very quickly at high baud rates, it is possible for the Wombat to drop characters. This public data increments every time a byte is received that the Wombat is unable to process an incoming byte. This public data can be used to monitor from the host, or with the pulse mode to beep or blink a light on an overflow. |
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| 252 | Buffer Zero Value This data is designed for testing and initialization purposes. It always returns zero |
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| 253 | Random Value This data will return a psuedo-random number based on a 32 bit Linear Feedback Shift Register with taps 32, 7, 5, 3, 2 and 1. It returns a different value each time it is accessed. It repeats every 65536 entries. It is seeded with 0x00000001 at powerup. The seed will be configurable in future versions of the Wombat Firmware. |