EPICS aiRecord记录的驱动程序开发实例

1、准备IOC环境

假设已经构建了EPICS Base，即是已经设置了环境变量EPICS_BASE，并且在系统搜索PATH中已经存在了EPICS的可执行文件。EPICS base在本机上的安装路径如下。

在EPICS路径下，用mkdir aiDirver创建一个目录，并且通过切换到这个路径下。用makeBaseApp.pl创建这个IOC程序框架。

root@orangepizero2:/usr/local/EPICS/program/aiDriver# makeBaseApp.pl -t ioc aiDriver
root@orangepizero2:/usr/local/EPICS/program/aiDriver# makeBaseApp.pl -i -t ioc aiDriver
Using target architecture linux-aarch64 (only one available)
The following applications are available:
    aiDriver
What application should the IOC(s) boot?
The default uses the IOC's name, even if not listed above.
Application name?
root@orangepizero2:/usr/local/EPICS/program/aiDriver# ls
aiDriverApp  configure  iocBoot  Makefile
root@orangepizero2:/usr/local/EPICS/program/aiDriver#

2、查看这个IOC程序的目录结构

root@orangepizero2:/usr/local/EPICS/program/aiDriver# ls -R
.:
aiDriverApp  configure  iocBoot  Makefile

./aiDriverApp:
Db  Makefile  src

./aiDriverApp/Db:
Makefile

./aiDriverApp/src:
aiDriverMain.cpp  Makefile

./configure:
CONFIG  CONFIG_SITE  Makefile  RELEASE  RULES  RULES_DIRS  RULES.ioc  RULES_TOP

./iocBoot:
iocaiDriver  Makefile

./iocBoot/iocaiDriver:
Makefile  st.cmd

1）configure目录中RELEASE文件中指明了这个IOC应用程序所依赖的其它EPICS模块，在本例中，只使用了base模块：

...
EPICS_BASE = /usr/local/EPICS/base
...

3、编写aiRecord的驱动程序

 1）aiDriverApp/src中存放了本例中为aiRecord记录编写的驱动程序devAiDriver.c：

#include 
#include 
#include 
#include 

#include "alarm.h"
#include "dbDefs.h"
#include "dbAccess.h"
#include "epicsMath.h"
#include "recGbl.h"
#include "devSup.h"
#include "aiRecord.h"
#include "epicsExport.h"

/* Create the dset for devAiDriver */
static long init_record(dbCommon *pcommon);
static long read_ai(aiRecord *prec);

aidset devAiDriver = {
    {6, NULL, NULL, init_record, NULL},
    read_ai, NULL
};

// 导出这个驱动程序
epicsExportAddress(dset, devAiDriver);

static long init_record(dbCommon *pcommon)
{
    aiRecord *prec = (aiRecord *)pcommon;

    srand((unsigned)time(NULL));
    prec->udf = FALSE;

    return 0;
}


static long readLocked(struct link *pinp, void *dummy)
{
    aiRecord *prec = (aiRecord *) pinp->precord;
    long status = 0;

    
    // 产生一个0-999之间的随机数
    prec->rval = rand() % 1000;

    if (dbLinkIsConstant(&prec->tsel) &&
        prec->tse == epicsTimeEventDeviceTime)
        dbGetTimeStamp(pinp, &prec->time);

    return status;
}

static long read_ai(aiRecord *prec)
{
    long status = dbLinkDoLocked(&prec->inp, readLocked, NULL);

    if (status == S_db_noLSET)
        status = readLocked(&prec->inp, NULL);

    return status;
}

2）然后编写一个dbd文件devAiDriver.dbd：

device(ai,INST_IO,devAiDriver, "Random Ai")

3） 修改同一级目录下的Makefile文件，添加以下两行：

aiDriver_DBD += devAiDriver.dbd
aiDriver_SRCS += devAiDriver.c

4） 进入目录aiDriver/aiDriverApp/Db中，编写记录实例文件：

root@orangepizero2:/usr/local/EPICS/program/aiDriver/aiDriverApp/Db# cat aiTest.db
record(ai, "$(TEST):AiRandom")
{
        field(DESC, "Test Ai Driver")
        field(SCAN, "1 second")
        field(DTYP, "Random Ai") # 指定设备驱动
        field(ASLO, "1.0")
        field(LINR, "NO CONVERSION")
}

5） 在与4)相同路径下的Makefile中添加以下一行：

DB += aiTest.db

4、编译这个IOC程序

切换到这个IOC的顶层目录，执行make，进行编译：

root@orangepizero2:/usr/local/EPICS/program/aiDriver# make
make -C ./configure install
...
make[1]: Leaving directory '/usr/local/EPICS/program/aiDriver/iocBoot'
root@orangepizero2:/usr/local/EPICS/program/aiDriver#

5、启动这个IOC程序

1）进入启动目录aiDriver/iocBoot/iocaiDriver，修改启动脚本st.cmd

#!../../bin/linux-aarch64/aiDriver

#- You may have to change aiDriver to something else
#- everywhere it appears in this file

< envPaths

cd "${TOP}"

## Register all support components
dbLoadDatabase "dbd/aiDriver.dbd"
aiDriver_registerRecordDeviceDriver pdbbase

## 装载记录实例
dbLoadRecords("db/aiTest.db","TEST=Random")

cd "${TOP}/iocBoot/${IOC}"
iocInit

2） 启动这个IOC程序，并用dbl查看这个IOC程序中加载的记录：

root@orangepizero2:/usr/local/EPICS/program/aiDriver/iocBoot/iocaiDriver# ../../bin/linux-aarch64/aiDriver st.cmd
#!../../bin/linux-aarch64/aiDriver
< envPaths
epicsEnvSet("IOC","iocaiDriver")
epicsEnvSet("TOP","/usr/local/EPICS/program/aiDriver")
...
epics> dbl
Random:AiRandom

6、通道访问

相同局域网中，通过安装通道访问库的计算机，访问查看这个Random:AiRandom记录

[root@main-machine blctrl]# camonitor Random:AiRandom
Random:AiRandom                2023-06-06 01:34:43.853698 682
Random:AiRandom                2023-06-06 01:34:44.853710 143
Random:AiRandom                2023-06-06 01:34:45.853702 869
^C

可以看到被访问的记录，每秒钟产生一个0-1000之间的随机数。 

总结：

以上详细描述了如何为一个EPICS记录开发驱动程序。此处开发的驱动程序是每秒为使用这个驱动程序的aiRecord提供一个0-999之间的RAW值。如果需要与具体硬件连接，请使用asyn模块。