Typical crystal values are 4 and 20mhz. Meqanique has not published their code for compiling, so you can not modify the crystal value that way, unless you get Meqanique to compile it for you. But there is a way to edit the baud rate value in the hex file, which lets you run at different crystal values. It is fairly easy if you have a PicKit2 programmer. Here are the instructions for modifying the hex file:
So far, all the hex files I have looked at specify the baud rate at address 7D06. But just in case, here is the check: Load the 4 mhz hex file into the PicKit2, and program your chip. Now load the 20 mhz hex into the PicKit2, but select verify. This will highlight the differences between the hex files. On the 18F2520, the first failure (variance) is at address 7D06. The last half of E040 is the serial BRGH=1 setting. 40 hex is 64 decimal, which gives the serial port 19,200 baud at 20 mhz. Since this chip is capable of 40mhz, we can change this setting to 129 decimal for 19,200 baud, which would be 81 hex. With the PicKit2, we can just type in the new value so we edit it to E081. Now you need to enter the correct configuration settings for your chip. This will need to be the PLL settings, and any other things that need to differ to run at this speed. Then hit the write button.
Here is the 18f4520 40mhz hex file:http://www.scalerobotics.com/18f4520_40.hex.txt
Re: Any faster option than USART 115,200?
no, divide by 10, 8 data + start + stop bits
richard Today, 03:16