Servo - May 2008

REVIVING AN ANDROBOT BOB: Part 4

New firmware loaded on co-processor (also mounting of footlight driver).

Getting New Code Into BOB

Whether the Handy Board is a new one and the firmware needs to be downloaded, you’re just sending down the latest Interactive-C program, or you’re just using the Interactive portion of Interactive-C, you need to have a connection to the Handy Board. This normally requires connecting a serial cable to a small charging adapter which then connects to the Handy Board via a four-pin RJ- 11 cable. The manual firmware download is a bit finicky in that the timing requirements are fairly strict and it uses a slower rate (1200 baud) than the normal communication speed (9600 baud) used by Interactive-C. Since it is rare that the firmware needs to be refreshed (thanks to the addition of the NVRAM mod), this isn’t much of a problem. We only need to do that again if the NVRAM gets corrupted

Close-up of A7 Engineering eb501-SER Bluetooth adapter.

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somehow or we want to download a newer image of the firmware.

Since BOB has his own brain on board, I wanted him to be autonomous like he was originally intended to be. I needed to easily send down new code as new features and routines were constantly created. The ability to use the interactive portion of Interactive-C helped speed development along. The solution was just to cut the cord and go wireless. Bluetooth works well to create this wireless link. On BOB, I am using an eb501-SER Bluetooth module from A7 Engineering that has both RS-232 level and logic level serial signals available. The connection to the Handy Board is pretty straightforward and only requires +5V, ground, RX, and TX. It just requires a custom four-pin adapter made from an old phone cable.

One end was cut off and a six-pin connector was installed to hook up to the 5V logic level connector on the A7 Bluetooth module. The four-pin modular connector on the Handy Board has the ground, RX, and TX already present. However, it was lacking the +5V supply since the power lead on the RJ- 11 jack is normally used to charge the Handy Board. Since the Handy Board in BOB has been modified to run off a 5V DC-DC converter, another modification was done to route this +5V to the RJ- 11 so it can power the Bluetooth module. The adapter for the hardwired connection was also modified so that it can be powered from the Handy Board, as well.

Many newer systems already have built-in Bluetooth adapters. However, these may be a Class 2 device with a range of only 10 m ( 33 ft). The adapter I used on the PC was a ZOOM Bluetooth USB adapter, model 4310. This is a Class 1 device with a small antenna so it is rated at 100 m (330 ft) to match the A7 Bluetooth adapter on the robot. This provides an excellent range of operation. The Bluetooth adapter looks like a serial port on the PC. The first time the adapters are used they have to be paired up with each other. It is a fairly straightforward process on the A7 module, but may be different for other Bluetooth adapters.

Once this is done, it should not need to be done again unless one of the adapters is swapped out. Now whenever BOB is powered up, it shows as an available serial port. It works great for downloading new programs into BOB and also working with him interactively. The only portion that poses a problem is the rare occasion for new firmware. It hasn’t been a problem yet, but I do plan on wiring up a DPDT switch to toggle between the Bluetooth serial device and the hardwired serial connection. If I ever do have to send down the low level firmware again, I can just flip a switch, plug in the Interface board, and send down the code. Once there, just flip the switch back and go back to wireless operation