SPI keyboard module for a parking meter and a parking meter having an SPI keyboard module
A serial peripheral interface (SPI) keyboard module for a parking meter comprises a plurality of key switches and at least one controller configured to detect a key press, determine a predetermined indicator associated with the pressed key and transmit the indicator to a keyboard interface of the parking meter. The SPI keyboard module provides a low power keyboard module that can be easily adapted to provide different keyboards or layouts without requiring significant changes to the parking meter electronics.
1. A parking meter comprising:
at least one parking meter controller executing instructions to configure the parking meter to provide:
operating functionality; and
a keyboard interface comprising a serial peripheral interface (SPI) bus interface; and
an SPI keyboard module connected to the at least one parking meter controller by an SPI bus, the SPI keyboard module comprising:
a plurality of key switches; and
at least one keyboard controller configured to:
detect pressing of a key switch of the plurality of key switches;
determine a predetermined indicator associated with the detected key switch that was pressed; and
transmit over the SPI bus the predetermined indicator associated with the pressed key to the keyboard interface of the at least one parking meter controller,
wherein the at least one parking meter controller receives the transmitted predetermined indicator associated with the pressed key and determines an associated functionality of the pressed key based on the received predetermined indicator,
wherein the keyboard interface determines a keyboard identifier of the SPI keyboard module and selects a keyboard mapping associated with the SPI keyboard module based on the keyboard identifier,
wherein the keyboard interface uses the keyboard mapping to map the received predetermined indicator to a particular key.
2. The parking meter of claim 1 , wherein the keyboard identifier is communicated to the operating functionality and the operating functionality enables or disables one or more features of the parking meter based on the keyboard identifier.
3. The parking meter of claim 1 , wherein the SPI bus comprises:
a chip select (CS) signal line associated with the SPI keyboard module for carrying a chip select signal indicative of when the keyboard module can transmit to the at least one keyboard controller;
a serial clock (SCLK) signal line for carrying a clock signal for controlling signal timing;
a master in slave out (MISO) signal line for carrying serially transmitted data from the SPI keyboard module to the at least one parking meter controller; and
a master-out-slave-in (MOSI) signal line for carrying serially transmitted data from the at least one parking meter controller to the SPI keyboard module.
4. The parking meter of claim 3 , wherein the keyboard controller is configured to:
monitor the CS signal line in a transmission mode when data is to be transmitted to the at least one parking meter controllers.
5. The parking meter of claim 4 , further comprising an attention (ATTN) signal line connecting the SPI keyboard module to the at least one parking meter controller, and wherein the keyboard controller is configured to:
switch from a sleep mode to the transmission mode when a key press is detected; and
raise a signal on the ATTN signal line providing an indication to the at least one parking meter controller that there is data to transmit.
6. The parking meter of claim 5 , wherein the keyboard controller is further configured to:
switch from the transmission mode to the sleep mode when there is no more data to transmit to the at least one parking meter controller.
7. The parking meter of claim 1 , wherein the keyboard controller detects pressing of the key switch by:
detecting a trigger indicative of pressing of the key switch; and
scanning the plurality of key switches to determine which key switch was pressed.
8. The parking meter of claim 1 , wherein the keyboard interface transmits a keyboard command comprising a command identifier to the SPI keyboard module over the SPI bus, and wherein the keyboard controller of the SPI keyboard module receives and processes the keyboard command.
9. The parking meter of claim 8 , wherein the keyboard command comprises one or more of:
a mode command changing an operating mode of the SPI keyboard module;
a configuration command setting a configuration parameter value of the SPI keyboard module;
a query command querying configuration parameter values of the SPI keyboard module; and
an action command causing the SPI keyboard module to perform an action.
10. The parking meter of claim 1 , wherein the SPI keyboard module further comprises a feedback device capable of providing feedback of key presses.
11. The parking meter of claim 1 , wherein the SPI keyboard module further comprises a light emitting diode (LED) device for lighting at least a portion of the plurality of key switches.
12. The parking meter of claim 1 , wherein the parking meter is a single space parking meter.
13. The parking meter of claim 1 , wherein the parking meter is a multi-space parking meter.
14. The parking meter of claim 1 , further comprising a second SPI keyboard module connected to the at least one parking meter by the SPI bus.
15. An SPI keyboard module for connection to a parking meter controller in a parking meter by an SPI bus, the SPI keyboard module comprising:
a plurality of key switches; and
at least one keyboard controller configured to:
detect pressing of a key switch of the plurality of key switches;
determine a predetermined indicator associated with the detected key switch that was pressed; and
transmit over the SPI bus the predetermined indicator associated with the pressed key to the keyboard interface of the parking meter controller; and
transmit over the SPI bus a keyboard identifier of the SPI keyboard module for use in selecting by the parking meter controller a keyboard mapping associated with the SPI keyboard module, wherein the keyboard mapping selected based on the transmitted keyboard identifier allows the parking meter controller to map the predetermined indicator to a particular key,
wherein the transmitted predetermined indicator allows the parking meter controller to determine an associated functionality of the pressed key based on the transmitted predetermined indicator.
16. The SPI keyboard module of claim 15 , wherein the SPI bus comprises:
a chip select (CS) signal line associated with the SPI keyboard module for carrying an chip select signal indicative of when the keyboard module can transmit to the keyboard controller;
a serial clock (SCLK) signal line for carrying a clock signal for controlling signal timing;
a master in slave out (MISO) signal line for carrying serially transmitted data from the SPI keyboard module to the parking meter controller; and
a master-out-slave-in (MOSI) signal line for carrying serially transmitted data from the parking meter controller to the SPI keyboard module.
17. The SPI keyboard module of claim 16 , wherein the keyboard controller is configured to:
monitor the CS signal line in a transmission mode when data is to be transmitted to the parking meter controllers.
18. The SPI keyboard module of claim 17 , further comprising a connector to an attention (ATTN) signal line for connecting the SPI keyboard module to the parking meter controller, and wherein the keyboard controller is configured to:
switch from a sleep mode to the transmission mode when a key press is detected; and
raise a signal on the ATTN signal line through the connector providing an indication to the parking meter controller that there is data to transmit.
19. The SPI keyboard module of claim 18 , wherein the keyboard controller is further configured to:
switch from the transmission mode to the sleep mode when there is no more data to transmit to the parking meter controller.
20. The SPI keyboard module of claim 15 , wherein the keyboard controller detects pressing of the key switch by:
detecting a trigger indicative of pressing of the key switch; and
scanning the plurality of key switches to determine which key switch was pressed.
21. The SPI keyboard module of claim 15 , wherein the keyboard controller is configured to receive and process a keyboard command comprising a command identifier over the SPI bus.
22. The SPI keyboard module of claim 21 , wherein the keyboard command comprises one or more of:
a mode command changing an operating mode of the SPI keyboard module;
a configuration command setting a configuration parameter value of the SPI keyboard module;
a query command querying configuration parameter values of the SPI keyboard module; and
an action command causing the SPI keyboard module to perform an action.
23. The SPI keyboard module of claim 15 , further comprising a feedback device capable of providing feedback of key presses.
24. The SPI keyboard module of claim 15 , wherein the SPI keyboard module further comprises an LED device for lighting at least a portion of the plurality of key switches.