Pololu Qik 2s9v1 Manuel d'utilisateur télécharger pdf (Page 14)

Pololu Protocol:

This protocol is compatible with the serial protocol used by our other serial motor and servo controllers. As such,

you can daisy-chain a qik on a single serial line along with our other serial controllers (including additional qiks)

and, using this protocol, send commands specifically to the desired qik without confusing the other devices on the

line.

The Pololu protocol is to transmit 0xAA (170 in decimal) as the first (command) byte, followed by a device-

number data byte. The default device number for the qik is 9, but this is a configuration parameter you can change.

Any qik on the line whose device number matches the specified device number will accept the command that

follows; all other Pololu devices will ignore the command. The remaining bytes in the command packet are the

same as the compact protocol command packet you would send, with one key difference: the compact protocol

command byte is now a data byte for the command 0xAA and hence must have its most significant bit cleared.

Therefore, the command packet is:

0xAA, device # byte, command byte with MSB cleared, any necessary data bytes

For example, if we want to set motor M1 to full speed forward for a qik with device number 9, we could send the

following byte sequence:

in hex: 0xAA, 0x09, 0x0D, 0x7F

in decimal: 170, 9, 13, 127

Note that 0x0D is the command 0x8D with its most significant bit cleared. Since all compact-protocol command

bytes start with 0x8n, these bytes will all turn into data bytes 0x0n.

The qik will respond to both the Pololu and Compact protocols on the fly; you do not need to use a jumper or

configuration parameter to identify which protocol you will be using.

Procedure for Daisy-Chaining

Daisy-chaining multiple qiks together on the same serial line is simple. Individually assign each qik a different

device ID using the set configuration parameter command (see Section 5.c), and then connect your TTL serial

transmit line to each qik’s RX line. If you wish, you can connect all of the qiks’ ERR lines to a single input on your

controlling module. When you issue your first Pololu-protocol command, the qiks will all automatically detect the

baud from the initial 0xAA byte.

Connecting multiple serial outputs to one serial input is more complicated. Each device will only transmit when

requested, so if each unit is addressed separately, multiple units will not transmit simultaneously. However, the

outputs are driven, so they cannot simply be wired together. Instead, you can use an AND gate (since the idle state

is high).

If you want to daisy-chain a qik with other Pololu devices that use 0x80 as an initial command byte, the

procedure becomes slightly more complicated. You should first transmit the byte 0x80 so that these devices can

automatically detect the baud rate, and only then should you send the byte 0xAA so that the qik can detect the

baud rate. Once all devices have detected the baud rate, Pololu devices that expect a leading command byte of

0x80 should ignore command packets that start with 0xAA and qiks will ignore command packets that start with

0x80.

4. Serial Interface Page 14 of 24

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Pololu Qik 2s9v1 Manuel d'utilisateur Page 14