I'm trying to control my East Tester ET5410A+ electronic load remotely with SCPI over its USB connection from a Raspberry Pi. But I'm not having any luck, and I can't figure out what is wrong.
I know the remote control works, because I can plug the USB cable into my PC and successfully issue commands using Tera Term (once the settings are configured for baud, local echo, LF-only, etc.).
*IDN?
ET5410A+ 09702312016 V1.01.2302.019 V1.06.2247.016
SYSTEM:VERSION?
V1.01.2302.019
SYSTEM:BEEP
Rexecu success
When I do this, the small 'lock' icon also appears in the corner of the ET5410A+'s screen to show it is in remote mode.
But I'll be damned if I can communicate with the thing on a Raspberry Pi. Nothing I try seems to work.
It's recognised by the system when I plug in the USB, so no issue there - the unit's CH340 USB-UART interface is listed by lsusb and there are no errors logged in dmesg. My user is also definitely in the 'dialout' group too.
pi@raspberrypi:~ $ lsusb
Bus 001 Device 006: ID 1a86:7523 QinHeng Electronics CH340 serial converter
Bus 001 Device 004: ID 0a5c:bd1e Broadcom Corp. BCM43143 802.11bgn (1x1) Wireless Adapter
Bus 001 Device 003: ID 0424:ec00 Microchip Technology, Inc. (formerly SMSC) SMSC9512/9514 Fast Ethernet Adapter
Bus 001 Device 002: ID 0424:9514 Microchip Technology, Inc. (formerly SMSC) SMC9514 Hub
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
pi@raspberrypi:~ $ dmesg
...
[ 8661.032917] usb 1-1.5: new full-speed USB device number 6 using dwc_otg
[ 8661.166494] usb 1-1.5: New USB device found, idVendor=1a86, idProduct=7523, bcdDevice=80.31
[ 8661.166563] usb 1-1.5: New USB device strings: Mfr=0, Product=2, SerialNumber=0
[ 8661.166594] usb 1-1.5: Product: USB Serial
[ 8661.184262] ch341 1-1.5:1.0: ch341-uart converter detected
[ 8661.187661] usb 1-1.5: ch341-uart converter now attached to ttyUSB0
pi@raspberrypi:~ $ groups
pi adm dialout cdrom sudo audio video plugdev games users input render netdev gpio i2c spi
But nothing seems to be able to communicate. I've tried minicom, picocom, tio. All either don't seem to actually send anything, or whatever it is they're sending isn't in the right format.
One thing I did from the Pi that
does actually work is echoing a string directly to the serial port, for example:
echo -e -n 'SYSTEM:BEEP\n' > /dev/ttyUSB0 causes the unit to beep. Of course, this isn't much use to query information, as I can't read anything back. With this method I'm also not sure how the serial port knows the correct baud rate (9600); perhaps it retains the setting from previous efforts with other programs?
Any suggestions?