Wixel VISA read over USB

[ijustlovemath]

Hi all,

I'm trying to use the Pololu Wixel (https://www.pololu.com/docs/0J46) to read data from a Dexcom transmitter using this wixel app: https://github.com/StephenBlackWasAlreadyTaken/wixel-xDrip

I'll spare you the details of reading the docs; the Wixel receives a packet from the transmitter and transmits that packet over USB. It converts the packet from something the transmitter sends to a 7 byte package: 4 bytes for a uint32 payload, 1 byte for a battery reading of the transmitter, and 2 bytes for a battery reading of the wixel.

When I do a VISA read (the wixel is on a COM port if that helps), the VISA comes up with an error: (Hex 0xBFFF0015) Timeout.

I know the wixel is transmitting over USB (using CTS, baud rate of 9600), as it's showing that it's connected to the transmitter. I just think my labview VI is set up incorrectly. I've attached it for critique. Any help would be very much appreciated!

[RavensFan]

Why don't you have the Serial Configure VI in there to be sure that the baud rate is set, termination character is disabled, and that it uses hardware flow control?

[Dennis_Knutson]

Can you post an image of the block diagram, I'm posting from my phone?

I'm not sure I understand how you know the widget is transmitting. Can you read the data in MAX or another terminal emulation program? You should do that before trying to write any code.

[ijustlovemath]

Added the serial configure, got a payload! But now it's giving this error: VISA:  (Hex 0xBFFF001E) The specified state of the attribute is not valid, or is not supported as defined by the resource.

What would be a good serial terminal to easily configure for a read? attached is a photo of the block diagram.

[Dennis_Knutson]

There are suggestions on the pololu web site. Your link was incorrect but it was easy to strip off the ) that you talked onto the end. Where In the documentation does it say to use cts? The web page says to start with no handshaking.

[ijustlovemath]

The website doesn't say to use CTS; but the app that I loaded on (wixel-xdrip, the C code for it is under apps/dexdrip/dexdrip.c in the github repository) has CTS in one of the comments about the serial transfer, so I figured that was best to use. Neither PuTTy nor CoolTerm is getting anything, even though the Wixel has no blinking yellow LED ( from the app, that means that it's connected to the transmitter). This is disconcerting to say the least. What do you suggest I try?

[RavensFan]

What input is that constant 32 wired into?  I'm sure that is why you have that error because neither 32 for a baud rate or for data bits would be valid for any COM device I've ever seen.

[ijustlovemath]

It's a 4 byte payload. I'll try changing it!

[RavensFan]

That number is for the number of data bits within the byte.  Usually either 7 or 8, most commonly 8.

Your 4 byte "payload"  is part of the 7 you wire into the VISA read so you can read 7 bytes.

[ijustlovemath]

Ah I see. I'm getting real payloads now, when I remember to close the resource. How do I interpret the value as a number?is my byte array implementation functional? I keep getting nonsensical numbers for the uint32