Embedded Linux: Hardware, Software and Interfacing
Dr. Craig Hollabaugh
DTR AC Control Circuit
During testing, target boards require rebooting or power cycling.
The target board's serial port is connected to tbdev1's ttyS0 for console communications.
The circuit shown below drives an AC output (OAC) module from ttyS0's DTR signal. Additional LEDs
indicate that AC power is on and drop the RS-232 voltage driving the OAC's internal LED.
While using minicom for console communications, you can drop DTR using minicom's modem hang up feature (ctl-a h).
This will turn off the OAC and power off the target board. Change minicom's modem and dialing (ctl-a o)
parameter DTR drop time to 5 seconds to allow for a complete power down of the target board.
The circuit also contains a bypass switch to force the target power on. Exiting from minicom can
drop DTR and power off the target.
The DTR AC Control circuit schematic
DTR AC Control Circuit construction
DTR AC Control Circuit in operation
This circuit is NOT UL approved. Use at your own risk!
