Project Depot
This site stores all the documentation of my projects.
Tuesday, July 7, 2015
Thursday, June 5, 2014
C-programming AVR-Timer
Use the code shown to figure out the Peripheral Clock that drives the timer if it's not obvious or you don't want to read the manual.
The peripheral clock on the XMEGA-A1-XPLAINED can be driven by 5 different clock sources and it can be scaled 3 times before it gets to the timer module.
By default the clock = 2 MHz and all prescaler are set to 1.
To set the desired time:
1) change the 16 bit timer period (TCC0.PER),
2) change the clock scaling (TC_CLKSEL_DIVx_gc)
RS485 Tranceiver
Wednesday, May 21, 2014
uC based DMX Transmitter
Simple Lighting Set |
DATA FRAME
Each DMX512 transmitter sends 512
packets of 8-bit dimming values, between 0 and 255, where 0 represents the
lights off and 255 represents the maximum intensity. The DMX512 protocol
requires the transmitter to continuously repeat (at least once a second) the
transmission of a frame as shown in the timing diagram in Figure1 and Table2.
STATE MACHINE
State1: SENDMBB - DMX Idle (Mark Before Break)
State2: SENDDATA - Send 512 bytes
State3: SENDMAB - DMX Idle (Mark After Break)
State4: SENDBREAK - Send Break
State1: SENDMBB - DMX Idle (Mark Before Break)
State2: SENDDATA - Send 512 bytes
State3: SENDMAB - DMX Idle (Mark After Break)
State4: SENDBREAK - Send Break
DMX512
DMX 512 is used to control
intelligent lights in professional stage lighting. It is an asynchronous
serial communication and is based on the EIA/TIA-485 (aka RS-485). RS-485
specifications allow only one driver to send data at a time, and up to 32 unit
loads (12-kΩ load x 32=375Ω) can be placed on the bus. Maximum distance
is 1500 ft using a twisted-shielded cable (e.g. microphone cable) and two
terminators, consisting of 120 Ω, 1/2W resistors. As a rule of thumb, the
data signaling rate (in bps) multiplied by the cable length (in meters) should
not exceed 10^8. For example, a system with a cable measuring 500 m
should not transmit data at speeds greater than 200 kbps (10^8/500).
DMX 512 can use good quality
microphone cables. The 3-pin XLR connector wiring is shown below:
DMX512 Connector: pin1=shield, pin2=Data-, pin3=Data+
|
DMX
512 data is transmitted at 250 kiloHertz (kHz). A single transmission
(DMX Packet) includes synchronizing elements and channel data for up to 512
channels (1 universe). RS-485 uses a daisy chain connectivity scheme and
requires termination at both ends of the cable.
DMX512 Protocol |
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