Misconceptions of the Rambo Driver

[Eaglezsoar]

I have recently received a PM from a user who wondered if he should buy a new laptop because after he installed the Rambo driver on it, he could not get
the driver to go over 115K in the baud rate field.
The baud rate is not important whatever it defaults to is fine. I have personally tested this by reducing the baud rate of the driver to 1200 baud and I had
no problems connecting Repetier Host to the printer. Install the driver, check that it shows up under your ports, record the com port # then get out of there.
The baud rate that is important is the one in Repetier host under Config, Printer Settings. That baud rate HAS to match the one in the firmware. I am
writing this to help people understand and not think they have to buy new computers.

[Captain Starfish]

Yep, if the baud rate on your computer won't go up to the default baud rate on the Rambo, you can just drop the baud rate used by both to something the computer can handle.

Here's the problem though.

To drop the baud rate in the firmware, you first have to connect to it. You can change the rate via the LCD with the v0.91 firmware but I don't remember seeing it on the v0.83 version.

So if your laptop won't get up to the default speed (250kBaud from memory) then you can't connect to tell the Rambo to slow down.

I don't know whether the Arduino software uses the same baudrate for uploading new firmware, but I wouldn't attempt a 0.91 upgrade until I had everything else working anyway.

[Eaglezsoar]

Yep, if the baud rate on your computer won't go up to the default baud rate on the Rambo, you can just drop the baud rate used by both to something the computer can handle.

Here's the problem though.

To drop the baud rate in the firmware, you first have to connect to it. You can change the rate via the LCD with the v0.91 firmware but I don't remember seeing it on the v0.83 version.

So if your laptop won't get up to the default speed (250kBaud from memory) then you can't connect to tell the Rambo to slow down.

I don't know whether the Arduino software uses the same baudrate for uploading new firmware, but I wouldn't attempt a 0.91 upgrade until I had everything else working anyway.

I think you misunderstood. The baud rate that is set when you install the driver means absolutely nothing in relation to the computer talking to the
printer. You install the driver, record its port number and you don't care or need to adjust the baud rate of that port. We are dealing with virtual usb
ports not serial ports. The only baud rates that matters is that of the host and that of the firmware, they have to match. Arduino also uses USB when it
connects to the Rambo and it only needs the port number in order to connect to the Rambo. For a long time a lot of people got hung up on the baud rate
of the driver, and it just doesn't matter. We have to start thinking of the com port created by the driver as a USB port not a serial port.
Your statement of (So if your laptop won't get up to the default speed (250kBaud from memory) then you can't connect to tell the Rambo to slow down.)
Is absolutely wrong. If your host baud rate matches that of the firmware and they don't connect then you have a bad USB cable, or a bad Rambo. The
driver baud rate has nothing to do with it. Don't believe it? Take a working host and go into your drivers com port and set the baud rate to 1200 or any low number then open your host and it will still connect. We have to stop thinking that the speed of the computer and the created com port has something
to do with connecting to the printer it does not.

[Captain Starfish]

Ahah, there's that moment of clarity.

It just dawned on me: we're not talking about a DB9 connector on the laptop with a crappy UART behind it that can't go over 192kBaud. We're not even talking about a USB/Serial converter that might not be able to cope. We're talking about a usb/serial converter sitting on the Rambo behind the USB connector, and we KNOW it's capable because everyone's using it. If the computer has a USB port then the computer's capable of the speeds required. So I'm just going to quietly find a place to hide because the scenario I was talking about will never occur.

Thanks, Eaglezsore - every day is a learning day.

[Eaglezsoar]

Ahah, there's that moment of clarity.

It just dawned on me: we're not talking about a DB9 connector on the laptop with a crappy UART behind it that can't go over 192kBaud. We're not even talking about a USB/Serial converter that might not be able to cope. We're talking about a usb/serial converter sitting on the Rambo behind the USB connector, and we KNOW it's capable because everyone's using it. If the computer has a USB port then the computer's capable of the speeds required. So I'm just going to quietly find a place to hide because the scenario I was talking about will never occur.

Thanks, Eaglezsore - every day is a learning day.

I'm glad you see the light! Now my goal is to get everyone to understand it before they waste their money buying new computers
that will not make any difference. Please, if you are reading this and do not fully understand it speak up so that everyone understands.

[geneb]

FYI, the baudrate the Arduino IDE uses to upload firmware is 9600.

g.

[Eaglezsoar]

FYI, the baudrate the Arduino IDE uses to upload firmware is 9600.

g.

That's good to know Gene. Thanks for finding that info.

[geneb]

No problem. I think folks get hung up on the volume of information.

The RAMBo appears to the host as an FTDI-232 based serial device - the chip is a very common one found in a number of different USB-Serial adapters. The Arduinos use them for simplicity and ease of use. Unless the person in question has a 15 year old laptop, it's not going to have any problems at all running at the 250000 baud rate that is the default with the RAMBo. The 115200 limitation with Macs is strictly a function of the driver, not the host computer itself.

[dpmacri]

No problem. I think folks get hung up on the volume of information.

The RAMBo appears to the host as an FTDI-232 based serial device - the chip is a very common one found in a number of different USB-Serial adapters. The Arduinos use them for simplicity and ease of use. Unless the person in question has a 15 year old laptop, it's not going to have any problems at all running at the 250000 baud rate that is the default with the RAMBo. The 115200 limitation with Macs is strictly a function of the driver, not the host computer itself.

I haven't seen a problem with the Mac I'm using (a 13" Macbook Pro from 2011) running at 250000. I suspect it's just Macs older than that.

[geneb]

It may be just a missing baud rate entry in Repetier-Host for Mac then. I wish they'd update that thing - it looks horrible in comparison to the Windows version.

g.

[626Pilot]

I've run at 115200 (using Linux, going to 250000 is a pain) and it's extremely rare that the buffer starves for data. It's really not that big a deal. I also tried running at 57600 but it caused instability in the connection.

[bubbasnow]

I've run at 115200 (using Linux, going to 250000 is a pain) and it's extremely rare that the buffer starves for data. It's really not that big a deal. I also tried running at 57600 but it caused instability in the connection.

Im running 57600 with my pi right now no issues!