EGS5 Hardware Interface Description
3.17 GPIO Interface
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EGS5_HD_v02.004
Page 72 of 123
2012-02-09
Confidential / Released
3.17
GPIO Interface
The EGS5 has 10 GPIOs for external hardware devices. Each GPIO can be configured for use
as input or output. All settings are AT command controlled.
The GIPO related AT commands are the following: AT^SPIO, AT^SCPIN, AT^SCPOL, AT^SC-
PORT, AT^SDPORT, AT^SGIO, AT^SSIO. A detailed description can be found in
.
When the EGS5 starts up, all GPIO lines are set to high-impedance state after initializing, as
described in
. Therefore, it is recommended to connect pull-up or pull-down resis-
tors to all GPIO lines you want to use as output. This is necessary to keep these lines from float-
ing or driving any external devices before all settings are done by AT command (at least
AT^SPIO, AT^SCPIN), and after closing the GPIOs again.
3.17.1
Using the GPIO10 Line as Pulse Counter
The GPIO10 line can be assigned two different functions selectable by AT command:
•
The AT^SCPIN command configures the line for use as GPIO.
•
With AT^SCCNT and AT^SSCNT the line can be configured and operated as pulse counter.
Both functions exclude each other. The pulse counter disables the GPIO functionality, and vice
versa, the GPIO functionality disables the pulse counter. Detailed AT command descriptions
can be found in
The pulse counter is designed to measure signals from 0 to 1000 pulses per second. It can be
operated either in Limit counter mode or Start-Stop mode. Depending on the selected mode
the counted value is either the number of pulses or the time (in milliseconds) taken to generate
a number of pulses specified with AT^SCCNT. For reliable pulse detection a duty cycle of 50%
on a pulse signal with 1000 pulses per second is required. This means, that a "low"- resp.
"high"-signal duration of at least 500µs is required. Shorter signals may lead to inaccuracy of
the pulse detection.
In Limit counter mode, the displayed measurement result (URC “^SSCNT: <count>”) implies
an inaccuracy <5ms. In Start-Stop mode, you can achieve 100% accuracy if you take care that
no pulses are transmitted before starting the pulse counter (AT^SSCNT=0 or 1) and after clos-
ing the pulse counter (AT^SSCNT=3).
