See the latest version on the documentation wiki.
The #twatch can be updated from a PC on the local network thanks to Microchip’s network bootloader. Bug fix updates, new features, and alternate functions can be programmed into the #twatch using the bootloader. The 18F ethernet PICs can only be programmed an average of 100 times, so upgrades are somewhat limited.
This guide is taken from the main #twatch article. Read about the update procedure after the break.
If you’re using a brand new chip you’ll need to program the bootloader into the PIC18F67J60 through the ICSP header, then you can upload the #twatch firmware over the network. Program twatchv2-bl-vxx.HEX into the chip with a PIC programmer like an ICD2 or PicKit.
When the #twatch powers on, the bootloader runs before the main program starts. The bootloader checks for a connection between the PGD and PGC pins of the programming header, shown in the image above. If it finds a connection, the bootloader takes over and waits for new firmware to be uploaded.
There’s a very minor chance that the bootloader will accidentally start even without a jumper between the PGC and PGD pins. This won’t damage the #twatch, just disconnect the power supply and try again. Accidental bootloader entry can be prevented by moving the jumper over one position so it connects the PGD and GND pins.
The #twatch bootloader uses the IP address 192.168.1.123 and subnet mask 255.255.255.0. Your computer must also have an IP address that begins with 192.168.1.xxx to communicate with the #twatch. We chose the 192.168.1.xxx range because it’s a common default for home networks. If your computer uses another IP address range, you’ll need to temporarily adjust it before you can do the update.
How to upgrade:
- Ensure your PC is in the same IP range and subnet as the #twatch. Your PC should have an IP address in the range 192.168.1.xxx, and a subnet mask of 255.255.255.0. The default #twatch bootloader IP address is 192.168.1.123, make sure that no other computer connected to the same router already uses this address.
- Unplug the #twatch power supply.
- Put a jumper between the PGC and PGD pins.
- Plug in the network cable, if necessary, and plug in the power supply. The screen may be blank, have solid blocks, or garbage.
- Use a TFTP utility to send the new firmware to the #twatch IP address, we use TFTP.exe from the Windows command line.
- The TFTP update reports success or error.
- Unplug the power supply, remove the update jumper.
- Plug the power supply back in. The #twatch should start scrolling tweets. If the bootloader starts instead, put a jumper between the PGD and GND pins and try again.