UART device Service - This device service is used to connect serial UART devices to EdgeX
- Function:
- This device service is used for universal serial device, such as USB to TTL serial, rs232 or rs485 interface device. It provides REST API interfaces to communicate with serial device
- This device service ONLY works on Linux system
- This device service is contributed by Jiangxing Intelligence and HCL Technologies(EPL Team)
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This Device Service runs with other EdgeX Core Services, such as Core Metadata, Core Data, and Core Command
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The uart device service contains many pre-defined devices which were defined by
res/devices/device.uart.toml. The devices in this file are created by the uart device service in core metadata when the service first initializes. -
It has a generic profile which supports read and write. Depends on the application requirements this profile can be used to connect any kind of serial device.
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device.uart.generic.yamldescribes the generic profile used read and write to the serial device. As an example, it has two device resources - one for read and another for write. The device command is used to read the read value. Depends on the application requirements, the device resources need to be added. The autoevents in the device.uart.toml file can be enabled or disabled as per the requirements. The parameters 'maxbytes' and 'timeout' are needed for uart read. 'maxbytes' indicates the maximum number of bytes that particular device resource can read. 'timeout' in seconds is used for read so that the read call does not block forever. Ensure timeout is used for write device resource also.name: "Uart-Generic-Device" manufacturer: "edgex" model: "edgex-uart" labels: - "device-uart-example" description: "Example of Device-Uart" deviceResources: - name: "Read_UART" isHidden: false description: "used to read from the UART device" attributes: { type: "generic", dev: "/dev/ttyAMA1", baud: 115200, maxbytes: 160, timeout: 1} properties: valueType: "String" readWrite: "R" - name: "Write_UART" isHidden: false description: "used to write to the UART device" attributes: { type: "generic", dev: "/dev/ttyAMA1", baud: 115200, timeout: 1} properties: valueType: "String" readWrite: "W" deviceCommands: - name: "Read_Cmd" readWrite: "R" resourceOperations: - { deviceResource: "Read_UART" }
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After the uart device service has started, we can communicate with these corresponding pre-defined devices.
Here we give the step by step guidance examples of using this device service. In these examples, we use RESTful API to interact with EdgeX (please notice that, you still need to use Core Command service rather than directly interact with UART device service).
Since the edgex-cli has released, we can use this new approach to operate devices:
edgex-cli command list -d Uart-Transceiver-Device
If you would prefer the traditional RESTful way to operate, you can try:
curl -X 'GET' http://localhost:59882/api/v2/device/name/Uart-Generic-Device | json_pp
Use the curl response to get the command URLs (with device name and resource) to issue commands to the UART device via the command service as shown below. You can also use a tool like Postman instead of curl to issue the same commands.
{
"apiVersion" : "v2",
"deviceCoreCommand" : {
"coreCommands" : [
{
"get" : true,
"name" : "Read_Cmd",
"parameters" : [
{
"resourceName" : "Read_UART",
"valueType" : "String"
}
],
"path" : "/api/v2/device/name/Uart-Generic-Device/Read_Cmd",
"url" : "http://localhost:59882"
},
{
"get" : true,
"name" : "Read_UART",
"parameters" : [
{
"resourceName" : "Read_UART",
"valueType" : "String"
}
],
"path" : "/api/v2/device/name/Uart-Generic-Device/Read_UART",
"url" : "http://localhost:59882"
},
{
"name" : "Write_UART",
"parameters" : [
{
"resourceName" : "Write_UART",
"valueType" : "String"
}
],
"path" : "/api/v2/device/name/Uart-Generic-Device/Write_UART",
"set" : true,
"url" : "http://localhost:59882"
}
],
"deviceName" : "Uart-Generic-Device",
"profileName" : "Uart-Generic-Device"
},
"statusCode" : 200
}Assume we have a FT232 (USB to serial UART interface) uart device connected between raspberry pi 4b and a PC. Raspberry Pi is running the edgex and the uart device service. Then we can send the string "12345" from the raspberry pi to the PC using the below command. This will print '12345' in the PC's serial application. Ensure timeout is used for write device resource.
# Send the write command
$ curl -X 'PUT' "http://localhost:59882/api/v2/device/name/Uart-Generic-Device/Write_UART" -d '{"Write_UART":"3132333435"}' | json_pp
% Total % Received % Xferd Average Speed Time Time Time Current
Dload Upload Total Spent Left Speed
100 64 100 37 100 27 4020 2934 --:--:-- --:--:-- --:--:-- 8000
{
"apiVersion" : "v2",
"statusCode" : 200
}Assume we have the same FT232 device connected between raspberry pi 4b and a PC. Raspberry Pi is running the edgex and the uart device service. Send the data abcdef(616263646566 in hex) from the PC serial application to Raspberry Pi. Then receive that data using the below command.
# Receive data from the PC
$ curl -X 'GET' "http://localhost:59882/api/v2/device/name/Uart-Generic-Device/Read_UART" | json_pp
% Total % Received % Xferd Average Speed Time Time Time Current
Dload Upload Total Spent Left Speed
100 464 100 464 0 0 51475 0 --:--:-- --:--:-- --:--:-- 58000
{
"apiVersion" : "v2",
"event" : {
"apiVersion" : "v2",
"deviceName" : "Uart-Generic-Device",
"id" : "76b1880b-597b-4be9-b406-249cabb84a2f",
"origin" : 1662742218037556552,
"profileName" : "Uart-Generic-Device",
"readings" : [
{
"deviceName" : "Uart-Generic-Device",
"id" : "d5abbf8e-9947-47f1-855f-50f4179e10e7",
"origin" : 1662742218037556552,
"profileName" : "Uart-Generic-Device",
"resourceName" : "Read_UART",
"value" : "616263646566",
"valueType" : "String"
}
],
"sourceName" : "Read_UART"
},
"statusCode" : 200
}