As mentioned in the previous post, due to the fact that we were downloading the Motorola S-record file ‘main.srec’ via Serial Bootloader (using meshprog on Linux), fuse bits were not getting updated. If we had used JTAG interface (e.g using DRAGON Kit) and aurdude, this would have happened. S-record can have application code as well as fuse bit setting, unlike Intel Hex format.
This meant that the default TinyOS setting of 8 MHz for clock rate was not appropriate for this since Meshbeans are set for 4 MHz by default. So to get the Serial Communication working, we had to make the following changes:
1. Check the following in
tinyos-2.x/tos/platforms/meshbean/hardware.h
=> change clock rate to 4 MHz by
#define MHZ 4
=> Change here the default baud rate, if you need – 57600 works fine for me
#define PLATFORM_BAUDRATE 57600L
2. make sure that:
“The file chips/atm128/Atm128Uart.h contained some wrong constants, which produce strange results. The correct ones can be found in the ATmega 1281 datasheet and are:
ATM128_38400_BAUD_8MHZ_2X = 25
ATM128_57600_BAUD_8MHZ_2X = 16”
This change would not have effect on 4 MHz clock that we are using but its best to correct them anyway. Anyother Baud Rate combination can also be added.
I must add here that give a choice use a crystal which gives less errors – e.g. 3.6864 MHz instead of 4 MHz , similarly 7.3728 MHz instead of 8 MHz. (See the ATMega128a manual).
3. With these changes done, now one can try TestPrintf utility. Do read this README file :
http://www.tinyos.net/tinyos-2.x/apps/tests/TestPrintf/
I was first looking at serial data using MiniCom – this was producing some unprintable characters including what is expected. One has to use the Jave client to get the proper message displayed as output of Printf command. I used the following command to get the data displayed right:
java net.tinyos.tools.PrintfClient -comm serial@/dev/ttyUSB3:57600
Here /dev/ttyUSB3 is the port to which my meshbean module was connected vis USB port.
This would give the this output in a loop:
Hi I am writing to you from my TinyOS application!!
Here is a uint8: 123
Here is a uint16: 12345
Here is a uint32: 1234567890
