K-NET bus. When several turrets are connected to the K-Bus, the structure of the system is as showns

Transcription

1 K-NET bus The K-Net bus is based o the SPI bus but it allows to addressig may differet turrets like the I 2 C bus. The K-Net is 6 a wires bus (4 for SPI wires ad 2 additioal wires for request ad ackowledge sigals) : - /CS COM (stadard SPI sigal) Chip select - SCK (stadard SPI sigal) Clock - (stadard SPI sigal) Master Out Slave I - (stadard SPI sigal) Master I Slave Out - (additioal sigal) Commuicatio request - (additioal sigal) Ackowledge Whe several turrets are coected to the K-Bus, the structure of the system is as shows MASTER SLAVE #0 SLAVE #1 SLAVE #2 All slave turrets are i IDLE state ad are waitig for a message. All pis of each turret are i iput mode. Oly oe turret at the same time is allowed to cofigure the ad pis as output. If two or more turrets set those two lies as output, a bus coflict occurs. Whe the master wats to commuicate with a turret, it seds the umber of the turret. If the selected turret is preset, it sets the ad lies as output, ad commuicatio betwee the two modules may be performed. For example, whe the master ad the turret #1 are commuicatig, the system ca be pictured :

2 MASTER SLAVE #0 SLAVE #1 SLAVE #2 Whe all messages have bee set, the slave turret switches to Idle, i.e it sets all K-Net sigals as iput. Protocol : The commuicatio betwee the master ad oe of the turret is doe i three phases. a) Request (The master sigals that after about 500 µs it starts a ew message) b) Sed (Each byte set has to be ackowledged by the turret c) Receive (The turret sigals that a byte is ow ready ad the master ca get it) /CS COM SCK a b c see 2.5 (page 10 & 11) of the Khepera bus ad turret specificatios documetatio

3 At first, all SPI pis of slave turrets are cofigured as iput. The master geerates a low pulse o the sigal for idicatig that he would like to sed a message. The master wait about 500µS ad sed the first byte. The first byte cotai the umber of the selected turret ad is recieved by all turrets. All turrets check if the umber set by the master correspods to its ow turret umber ( routie rtrid i COM.ASI ).The correct turret the modifies the ad pi cofiguratio to be used as output sigals ad eable the SPI iterrupt. A high pulse o the lie idicates that the turret is preset ad waitig for the ext byte. All other uchose turrets disable the SPI iterrupt, set all SPI pis as iput, ad wait for the ext low pulse of. The ext byte set by the master is a trasactio umber ( routie rtrtrasactio i COM.ASI ). The trasactio umber is chose by the master before each commuicatio with a turret. The turret does t careabout this umber but idicates with a pulse o that it has correctly received the trasactio umber. The third byte set by the master is the legth of the followig message to be sed ( routie rtrlmsg i COM.ASI ). The legth uit is i byte. Now, the turret kows how may bytes will be sed. Oce agai, a pulse o the lie is geerated to idicate that the byte was correctly received. The ext bytes are the stored i a buffer ( routie rtrmsgok i COM.ASI ). All received bytes are ackowledged by a pulse o. Whe the etire message is received, a flag is set to TRUE (vit_com). The master the stop the trasmissio, so o more SPI iterrupts are geerated ad the COM_dialog routie is executed. The COM_dialog routie checks to see if the previous commad existes i the turret order table. The turret order table is declared at the top of the file NET.ASI ad cotais the header of the commad (1 byte), the legth of the aswer (with header) (1 byte), the address of the routie to be executed (2 byte) ad the ackowledge (1 byte). If the commad is ot foud i the turret order table, the turret goes ito the IDLE state ad waits for a reset. Otherwise, the address of the routie to be executed is called. I this routie, the slave must sed data to the master, so the turret puts the bytes to be set o a register ad idicates with a pulse o the lie that the byte is ready to be se. Fially, the master seds 8 pulses o the SCK lie ad reads the byte o the lie. This operatio is repeated util the aswer is completely set.

4 State diagram Pusle Turret ID correct Disable SPI Eable SPI & iput mode & output mode Get trasactio umber Get legth of the message Get (from order table) the legth of the aswer Get byte Ed of aswer Ed of message

5 Before sedig orders to a turret : All commads of the turret are declared i a table at the ed of the file NET.ASI. The size of this table is 20 * 6 = 120 bytes (20 fuctios, each with 6 parameters) ad it must ot be chaged. Each fuctio is declared as follows : Byte 1 : Byte 2 : Byte 3 : Byte 4 : Byte 5 : Byte 6 : turret umber commad header message legth (whole message) message legth (usable message) aswer legth ackowledge character For example, the commad B (get versio) is declared (i CALM otatio): kidtourelle, B, 3, 1, 3, b The master must kow the structure of all the turret s commads, so whe the robot is switched o, the master check for all turrets (umber 0..31) ad waits to receive the descriptio table for each turret. The master seds to each turret the byte X (see Order X)., which the returs 120 bytes (the table which cotais the turret 20 istructios). The followig 4 commads exists for all turrets : Comamd B : ( routie rgetvers ) The commad B returs the versio ad the revisio umber of the software cotaied i the turret µp. Commad X : ( routie rgetord ) The commad X seds turret table descriptio to the master. This table is declared at the ed of the file NET.ASI ad allows up to 20 differet commads. NOTE : the size of the table must ot be modified (the size must be 20*6= 120 bytes) Commad Y : ( routie rgetidt ) This commad returs the turret specificatio For example, a gripper returs : Gripper 1 Gripper, EF-96: Rev ad a K213 visio turret returs K213 2 Liear 64 pixels visio, EF-99: Rev The turret specificatio is declared at the top of the file NET.ASI

6 Commad Z : ( routie rrese ) This commad tests if the commuicatio with a turret is OK (echo). The master seds the character Z ad if the commuicatio with the selected turret is OK, he receives a lowercase z.