Serial Wombat
a general-purpose digital interface
device for hobbyists, engineers and students
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Serial Wombat PWM Direct Channel Mode
The Serial Wombat can drive any of it's I/O pins to provide a PWM output. Pins 16 and 17 have hardware assistance to provide 10 bit PWM resolution at high speeds. All other pins can provide slower PWM outputs, at 4 bits of resolution. The input format is the same regardless of whether the pin is driven in software or hardware. A number from 0 (0% high) to 65535 (100% high) represents the PWM. The 10 bit hardware PWM channels will more accurately intermediate numbers than the 4 bit software PWMs. This format allows compatiblity across all pins, regardless of their resolution.
The PWM direct channel mode allows the host to command the Wombat to generate a PWM on a pin.
Message format:
| Data Sent to the Wombat: | 200 | Pin # | 18 | PWM Duty cycle MSB | PWM Duty Cycle LSB | 0x55 | 0x55 | 0x55 | |
| Meaning: | Configure Pin First message | Pin Number to be set to PWM output | PWM Direct Mode | A number from 0 to 65535 representing a duty cycle from 0% to 100% | Unused | Unused | Unused | ||
| This message is echoed back by the Wombat. | |||||||||
Example:
Configure channel 16 to generate a 75% pwm output.
200 16 18 0xC000 0x55 0x55 0x55 ; Set pin 16 PWM Direct Mode
; .75 * 65536 = 0xC0000