Cybot Processor 2 Board

As I surmised back on the Processor 1 board, this board includes a 'brown out' circuit, which cures the missing reset resistor problem on the Processor 1 board. It's a standard 'brown out' circuit, using a PNP transistor and three resistors, the reason for using one is to help prevent problems due to supply fluctuations, if the supply drops momentarily it could confuse the processor, yet not drop low enough for it to generate a reset. The 'brown out' circuit overcomes this, causing a reset pulse to be generated if the supply fluctuates enough to upset the processor. The rest of the circuit is also standard, it uses a 4MHz ceramic resonator for the oscillator, and a total of six pull-up resistors, two of which are on the two wire bus between the processors, and are in parallel with the similar resistors on the Processor 1 board. The other four are on pins that connect to the expansion connector for the next board (Sonar I/O), presumably to hold inputs high which will be pulled low by some signals from that board - the Sonar I/O board includes the mode switch, which is four way, so it looks like it will feed to these pins. This gives a possible 16 values from the switches, from '0000' to '1111' binary (0 to 15 decimal) - as Cybot still works in 'light follow' mode, it appears that '1111' (decimal 15) is the setting for this mode. The other connections to the sonar I/O are via pins 2 - 6, all of which connect to Port P6 of the processor, and the power and ground rails on pins 11 - 13. The six pin connector from the Processor 1 board also carries a socket on top, this allows further boards to plug into it, and connect to all the required rails. 

Mode Pin 10 Pin 9 Pin 8 Pin 7
Fast light seek 1 1 1 1
Slow light seek 1 1 1 0
Fast avoid objects 1 1 0 1
Slow avoid objects 1 1 0 0
No response 1 0 1 1
Line follow 1 0 1 0
Follow objects 1 0 0 1
Line follow 1 0 0 0
With this board fitted, the piezo speaker now starts to work, giving four  short 'beeps' when you turn Cybot on, corresponding to the setting of the (yet to be fitted) mode switch - when the pins are high you get short 'beeps', and when the pins are low you get long 'beeps', so it gives you an audible indication of the mode you have set. Another effect of this board is that the light seeking mode now runs at full speed, without the mode switch in circuit it defaults to 'fast light seek', whereas before this board was fitted it executed 'slow light seek', if you connect a wire between pins 13 and 7 of the connector it restores 'slow light seek' mode.

This table shows Cybot mode settings identified so far, some are identified by testing, others from details posted by advance members who have the necessary hardware to run the different modes. The second half of the table, with Pin 10 = 0 isn't shown, as there's no response to any of them at the present time. To set Cybot to any of  these modes all you need to do is connect the pins labeled '0' down to ground - which is pin 13, you can do this simply by inserting pieces of thin solid core wire and connecting them together.

The outputs to the ultrasonic transmitters are on pins 5 and 6 of the connector, fed from pins 7 (P61) and 8 (P62) of the processor. Interestingly P61 outputs four cycles of 40KHz negative going every 25mS, and P62 outputs four cycles of 40KHz positive going every 25mS, presumably the reason for this inversion will be obvious when the Sonar I/O board is available for examination. Both pins output their signals regardless of mode setting, so Cybot transmits it's ultrasonic output at all times. Pin 4 of the connector causes both motors to reverse in 'avoid objects' mode, with pin 4 low (without the Sonar I/O board) both motors run backwards, when pin 4 is taken high, both motors then run forwards - in 'slow avoid' the motors run about 50% speed, in 'fast avoid' at 100% speed. In 'follow objects' mode both motors again run backwards, but this time when pin 4 is taken high both motors stop. In all sonar modes the response to pin 4 going high is immediate, but taking pin 4 low again takes a few seconds to get a response. Pins 2 and 3 seem to have no effect with the simple tests I've carried out, but it should all become clear when the Sonar I/O board is released.

While the chip only carries 'in-house' markings, without a manufacturers name, the pin configuration is identical to an 18 pin PIC but is actually another Elan processor, the EM78P156E - but the power and ground connections go to the same pins, the MCLR (reset) pin is connected to the brown-out circuit, the external oscillator components go to the same pins, the timer input is on the same pin, you could certainly drop an 18 pin PIC straight in this board. This Elan processor has 1Kb of OTP 13 bit program memory, and 48 bytes of 8 bit RAM, there are two versions listed on the Elan website (the 156EL and 156EH), and it's not clear which RealRobots use, but I suspect it's actually the 156EH as the only difference appears to be in the supply voltage range, and the EH version is more than enough for Cybot.

If you want to investigate the circuit further, you can download the processor datasheet from the manufacturers website, or direct from mine.

The picture of this board on the RealRobots website is of a different board, presumably the one used in the advance members units, it uses a 14 pin device, probably a PIC 16C505 - as that was the device used on the advance members Processor 1 boards.

Cybot graphics used by kind permission of Eaglemoss
Last Updated 18/02/02 You can reach me by email at: nigelg@lpilsley.co.uk