TTL Ports – Button Pumps
On the normal button/display pumps or bench pumps, the ttl output ports are available on the DB9 connector on the rear panel. This connector is not the RS-232 port!
The following chart shows the pin input and output assignment.
To guarantee recognition of logic levels, voltages on the input lines must be within the following
- TTL logic low (0): 0 to 1.5 V
- logic high (1): 3.5 to 5.25 V
TTL Ports – OEM Pumps
The OEM pump models are configured for installing in equipment of your design. As such the pump control circuit board is set up to take soldered connections rather than a single plug.
This diagram from the OEM Pump Manual shows the solder pad location and the location of current limiting resistors.
Accessing Ports Via RS232
The logic levels of pins 2, 3, 4, and 6 can be queried from an attached computer using the RS-232 ‘IN’
command and the output logic level of pin 5 can be set with the RS-232 ‘OUT’ command. There’s more details in your pump manual.
Power on Pin State
Unfortunately neither model of the pump appear to remember the last state of the TTL outputs after power cycling. All the pins appear to come on high at switch on regardless of previous state.
Users of the Valve Control Box
If you’re a user of the Valve Control Box inverting the signal is just a matter of changing the valve activate switch from Infuse to Withdraw.