UART problem with MSP430 to RN-42 HID

Wireless & IoT
1

Greetings,

I have an issue that has me stumped and I could really use some insight…

Here’s my circuit:

MSP430g2353 conected to launchpad usb

BlueSmirf RN-42 HID (for keyboard functionality) is connected to the Vcc and GND of the launch pad so they are operating at the same voltage.

The msp430 UART TX is connected to the RN42 Rx

RN-42 HID is paired with an android tablet and is recognized as a keyboard. Hardware keyboard is enabled.

I used GRACE in CCS5 to configure the USCI to a baud of 115200, the default of the RN 42. According to the HID maunal, if I send ascii ‘a’ over the uart it should type an “a” on the receiving end. It does nothing however. At one point, I sent about 10 ascii ‘a’ commands to it and all I got was a capital X. Looking at the binary values for ‘a’ and ‘X’ I can see how an offset in the reading of the data could explain this glitch, but I have no idea why it would happen or how to fix it. I have since been unable to replicate the ‘X’ glitch. I assume a simple wire between TX to RS is sufficient?

I’m afraid I’m stuck if I can’t figure this one out. I have limited tools to test with, if nobody has any ideas I may have to buy a UART to RS-232 converter and plugin to a PC to try and see what’s going on. That means more waiting and more money :frowning:

2

I am working on the SPP variant of the BlueSmirf with the MSP430.

I noticed that when the Launchpad was set to 115200, it would cause the USCI_A UART to drop characters from the conversation. So, for example, when I would try to go to command mode, I would expect to see “CMD\r\n” from the BlueSmirf, however what I’d get instead would be something like “CM\r\n” or “CD\r\n”.

I believe the problem is that the high baud rate requires a crystal to keep it in sync (this is just a guess, I’m just a hobbyist with no experience in electronics). The way I fixed it was to reconfigure the bluesmirf to 9600 baud. Then when you reboot it, connect to it with your MSP430 also configured for 9600 baud. That worked for me. I am not sure if your HID keyboard will work with 9600 baud but it is good for me. I haven’t had any trouble receiving characters in 9600 baud.

Hope this helps. I would appreciate if you could let me know if you figure out how to get it working at 115200 baud… (I don’t need that speed but I’m curious)