Hi, I have the Grove LCD RGB from Seeed and I am trying to use node-red-contrib-i2c to display text on it. There are 3 nodes: one to scan for devices on i2c bus, one to retrieve data from a device, and one to send data to a device.
This seems simple enough, but I cannot seem to configure the sending node properly to send text to the display.
When I use the scan node, I get back an array [62, 98, 112] and it definitely detects the presence of the LCD display (I have nothing else on the i2c bus). But I have no idea how to configure the sending node.
The parameters are as follows:
Address: (seems to want a decimal value, not hex)
Command: (seems to want a decimal value, not hex)
Payload: json?
Send Bytes: 1? 2?
I’ve spent hours trying too make this work, but no joy. I would be very appreciative if someone could shed some light on this. I love Node-RED, it is so easy to work with, but this one has me stumped!
Not used it but I can see that it has 2 I2C addresses 0x62 (98 decimal) for changing the colour of the backlight and 0x3E (62 decimal) for changing the text.
You can send a number of commands to the screen. For example to clear the text. Looks like you need to send a command to clear the screen, turn on the display, set the number of lines then send the text. Commands & text seem to be send using 2 bytes. The first byte is either 0x80 for commands or 0x40 for text.
Hello, thank you for that information. I had been studying that python code, but it didn’t get me anywhere. However, since you are saying I’m in the right place, I will go back and give it another try. Thanks very much for helping with this, I really appreciate it.
Node-RED has been very easy to use so far, and this is the first time I haven’t been able to make something work, but I guess that was inevitable.
Hi, so I have spent several hours trying every combination I can think of, but no joy. I’m wondering if someone could possibly provide an assist with some values that would actually do SOMETHING, perhaps even to just turn it on. I know it is working as I got it to work with other software that I don’t want to use:
Hi @cymplecy, thanks for your note. I had actually already copied your flow, and although it was helpful to see another perspective, I still wasn’t able to get my LCD display to work.
I should explain that I am a big supporter of Node-RED as I think it is a really great design environment for IoT. I think because it is part of the default install on a Raspberry Pi it will enable a lot of semi-technical folks (like myself) to explore the world of IoT, where they might not have done so before.
I don’t have any particular use for this Grove LCD screen (other than a general data read-out device) at the moment. What I am actually trying to do is fathom the i2c bus and help to produce a relatively straightforward way of using it. So I was hoping this particular node could be used as a somewhat standardized approach.
I am using the transparent Grove hat from SwitchDoc that does not require any translation drivers, so I am able to use the generic digital I/O nodes for the Pi, and those are working well. I was hoping this i2c node would provide a similar capability for the i2c bus.
I have followed your thread, but it seems to me it progressed to being a much more specific solution, with a different node that was designed specifically for your device.
I was hoping to be able to use the node-red-contrib-i2c 0.5.2 as a more generic solution, but I’m certainly open to anyone who has a better idea about how to use the i2c bus. I am still stumped, unfortunately.
At this point I think I will need to find someone we could pay to make this thing work as it is part of a larger project that we are undertaking. I realize that this may go against the grain of this voluntary forum, but perhaps there’s someone out there that would like some beer money?
The node-red-contrib-i2c is OK for playing around with I2C without having to write any code .
But to use any i2c device fully is going to require a specific node writing for them.
I don't think offer of beer money would work - I only drink 30 yr Islay for instance - it'll be more a case of someone with javascript/node skills who has a device and wants a node-RED node for it
Hi @cymplecy, perhaps you’re right, there may not be any such thing as a generic node for i2c, but I still think there’s room for a much better explanation of how this node works. I’ll see if I can tap into some of the resource groups I’m affiliated with.
I checked our cellar, but unfortunately there was no 30 year Islay left!
Thanks for your input, it was much appreciated. If I find out anything further, I will post it here.
- it'll be more a case of someone with javascript/node skills who has a device and wants a node-RED node for it