RoboteQ AX2850 - Manual (Page 165)

AX2550 Motor Controller User’s Manual 165
Automatic Switching from RS232 to RC Mode
Automatic Switching from RS232 to RC Mode
In many computer controlled applications, it may be useful to allow the controller to switch
back to the RC mode. This would typically allow a user to take over the control of a robotic
vehicle upon computer problem.
While the AX2550 can operate in either RC Radio or RS232 mode, the RS232 Data Input
and RC Pulse Input 1 share the same pin on the connector. External hardware is, therefore,
needed to switch this pin from the RS232 source or the RC Radio. The diagram in
Figure 93 shows the external hardware required to perform such a switch.
A third RC channel is used to activate a dual-throw relay. When the radio is Off, or if it is On
with the channel 3 off, the relay contact brings the RS232 signal to the shared input. The
second relay contact maintains the Power Control wire floating so that the controller
remains on.
When the RC channel 3 is activated, the relay turns On and brings the RC radio signal 1 to
the shared input. The second relay contact brings a discharged capacitor onto the Power
Control wire causing the controller to reset. Resetting the controller is necessary in order
to revert the controller in the RC mode (the controller must be configured to default to RC
mode).
The switching sequence goes as follows:
Upon controller power on with Radio off: (or Radio on with RC ch3 off)
• Controller runs in RC mode (must be configured in RC mode)
• Computer must send 10 consecutive Carriage Returns. Controller enters RS232
mode
Controller is on, Radio urns On with RC ch3 On
• Controller is reset, returning to RC mode
•
Controller will output the continuous parameter strings on the RS232 output. Com-
puter thus knows that RC mode is currently active. Computer sends Carriage
Return strings to try to switch controller back in RS232 mode. Since the RS232 line
is not connected to the controller, mode will not change.
RC3
RC1
RC2
TxData
RxData TxData
RC2/InputF
RC1/RxData
Power Control
Controller
4.7k
220uF
RC Radio
Computer
RC Activated
Switch
FIGURE 93. External circuit required for RS232 to RC switching