I seem to find only partial explanations regarding this question, I've used Bluetooth in previous projects but I plan to use it on an FPGA project. Currently The FPGA is connecting using a UART module. If I were to switch the UART module with a Bluetooth module, would their be any issues or would it work without any adjustments to the HDL code?
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\$\begingroup\$ What "Uart module" are you using, and which bluetooth module are you planning on using? And on which FPGA? \$\endgroup\$– PaulJun 8, 2015 at 17:39
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\$\begingroup\$ The project design is working on a DE0-nano originally it used a Waveshare FT232R. I have a few HC-05 and have access to other bluetooth modules at my local microcenter. I can't really find a UART unless I order which isn't an issue but if bluetooth can work as well then it makes little sense. \$\endgroup\$– kdgwillJun 8, 2015 at 18:04
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1\$\begingroup\$ I think the HC-05 works with AT commands, which might impact your code. Also, your FPGA runs 3.3V GPIO pins? And I've seen HC-05 (3.6V to 5.6V (basically 5V)). It might cause some trouble also. But apart from that, you could hook up your HC-05 instead of the FT232R. You can always try it? \$\endgroup\$– PaulJun 9, 2015 at 6:15
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1\$\begingroup\$ Well, the answer to your question, is NO, it will NOT work as simply as you thought. BT is a high level protocol, the UART is just a mean of transferring the data between the controller (your FPGA) and the BT controller. The HW part will work, but in order to actually get the BT to work, you need to configure it, sett it up and handle the data transfer using AT commands, you might be able to do it with HDL, but it would be much easier with a small controller such as NIOS. \$\endgroup\$– FarhadAJun 9, 2015 at 7:11
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1\$\begingroup\$ @FarhadA thank you. The module is actually just receiving commands from the computer and i'm actually using OR1k \$\endgroup\$– kdgwillJun 9, 2015 at 8:43
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The HC-05 indeed works with UART, though there are some points to consider.
AT commands
Also mentioned by FarhadA, the HC-05 uses AT-styled (not sure if it's conform the standard?) commands. This will mean that for setting the baud-rate you'll need to send AT+UART=9600,0,1 or something equivelant.source Though, if you run it on it's default baud-rate you might just get away with it. They seem to tunnel the UART messages out of the box (when using the default baudrate)source. Though checking of a device is connected and/or settings are done through AT commands. Thus might require changes in your code.
Working voltage
I've seen that these devices particulary run on 5V or (3.6V to 6V)source. So it might not work directly with your (3.3V?) FPGA. You'll need something to shift the voltage, there are some 'breakout boards' for this on the market (https://www.sparkfun.com/products/12009) but I guess there are various ways to achieve this.
The RN-42 seems to be 3.3V compatible source
