Differences

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--- en:netzer:i2c-master [2014/12/21 11:15] – Added framing feature. svesch
+++ en:netzer:i2c-master [2025/06/11 20:42] (current) – external edit 127.0.0.1
@@ Line 8: / Line 8: @@
 ===== NULL - The termination character =====
-The character //0x00// in the TCP/IP communication has special meaning in terminating any pending I2C transmission.
+The character //0x00// in the socket communication has special meaning in terminating any pending I2C transmission.
 If Netzer sends a //0x00// either the bus is busy, a bus collission occurred or a slave does not respond on address or data bytes.
 In the latter cases the bus is freed with a stop condition automatically.
@@ Line 21: / Line 21: @@
 ===== The start condition and the slave address byte =====
-A start condition is automatically announced on the bus, if Netzer gets the first character via the TCP/IP serial socket.
+A start condition is automatically announced on the bus, if Netzer gets the first character via socket.
 If an error occurs while announcing the start condition Netzer responds with a //0x00//.
 I2C protocol defines the very first byte after the start condition as slave address.
-Netzer sends a //0x00// via TCP/IP if no slave responds (ACK bit was '1').
+Netzer sends a //0x00// via socket if no slave responds (ACK bit was '1').
 Also a stop condition is initiated by Netzer.
-After the successful (means acknowledged) transmission of the slave address Netzer sends //0xFF// via TCP/IP.
+After the successful (means acknowledged) transmission of the slave address Netzer sends //0xFF// via socket.
@@ Line 43: / Line 43: @@
 If the R/W bit is **cleared** a transmission from master to slave is initiated.
-Each byte received by Netzer via the TCP/IP socket is directly sent to the slave (consider escaping!).
+Each byte received by Netzer via the socket is directly sent to the slave (consider escaping!).
-In response Netzer sends via TCP/IP either '0xFF' as positive acknowledge (ACK bit was '0') or //0x00// as negative acknowledge (ACK bit was '1').
+In response Netzer sends either '0xFF' as positive acknowledge (ACK bit was '0') or //0x00// as negative acknowledge (ACK bit was '1').
 In case of a negative acknowledge Netzer initiates a stop condition on the bus.
@@ Line 50: / Line 50: @@
 If the R/W bit is **set** a transmission from slave to master is initiated (clock is generated by I2C master).
-After the successful transmission of the slave address Netzer waits for further bytes on the TCP/IP socket.
+After the successful transmission of the slave address Netzer waits for further bytes on the socket.
-On receiving a byte via TCP/IP a byte is pulled from the slave and is sent via TCP/IP.
+On receiving a byte via socket a byte is pulled from the slave and is sent.
 In case the received byte is //0x00// the transmission is over and Netzer generates a stop condition on the bus.
 Any other value pulls the next byte from slave.
@@ Line 59: / Line 59: @@
 I2C supports repeated start. This symbol concatenates a stop and start condition while a I2C transmission is pending without freeing the bus inbetween.
-The special character //s// (0x73) in TCP/IP stream initiates the repeated start on the bus.
+The special character //s// (0x73) in socket stream initiates the repeated start on the bus.
 Therefore //0x73// must be escaped during normal stream transmission to Netzer.
 Exception to escaping //0x73// is the very first character (slave address) analog to the "General Call address" section.
-<WRAP center round important 60%>
 Receiving //0x73// from Netzer has no special meaning but //0x73// and therefore will not be escaped!
+<WRAP center round important 60%>
+Attention: This feature has changed since version 1.6: //0x73// is escaped in both directions.
 </WRAP>
@@ Line 75: / Line 76: @@
 Each action on the bus is considered like a socket frame terminated by //0x00//.
 This rule is applied for both directions.
+So each frame from host is replied by a socket frame.
 In case a frame is finished and no more frames wait for processing the socket is flushed.
-This leads to a higher throughput especially on TCP/IP connections.
+This leads to a higher throughput especially on network socket connections.
@@ Line 98: / Line 100: @@
+===== Examples =====
+The following examples presume that there is a [[connection|connection]] to Netzer.
+Take a look at the following picture for circuiting a I2C EEPROM IC as slave to Netzer.
+<imgcaption eeprom_example|Connecting a simple EEPROM to Netzer>{{:eeprom_example.png?direct}}</imgcaption>
+==== EEPROM slave address ====
+The EEPROM has the slave address 0x50.
+Because the LSB is reserved for the R/W indicator the address is shifted left by one: //0xA0//.
+==== Writing to the EEPROM ====
+See the following byte sequence for writing a //0x55// to memory address 0 of the EEPROM:
+<code>
+Write per socket to Netzer: 0xA0 0x5C 0x00 0x55 0x00
+Answer from EEPROM received from Netzer: 0xFF 0xFF 0xFF 0x00
+</code>
+  - //0xA0// is the slave address with the R/W bit cleared, means write access.
+  - Netzer returns //0xFF//, indicating the available slave.
+  - //0x5C 0x00// transfers the memory address 0 - of course must be backslashed ('\\' = 0x5C)
+  - Netzer returns //0xFF//, successful transfered memory address.
+  - //0x55// is the value written to EEPROM
+  - Netzer returns //0xFF//, successful transfered value.
+  - //0x00// stops the transmission - I2C bus is released.
+  - Socket sends //0x00// to the host - Frame termination
+==== Reading from EEPROM ====
+<code>
+Write per TCP/IP to Netzer: 0xA0 0x5C 0x00 0x73 0xA1 0xFF 0x00
+Answer from EEPROM received per TCP/IP from Netzer: 0xFF 0xFF 0xFF 0xFF 0x55 0x78 0x00
+</code>
+  - //0xA0// is the slave address with the R/W bit cleared, means write access.
+  - Netzer returns //0xFF//, indicating the available slave.
+  - //0x5C 0x00// transfers the memory address 0 - of course must be backslashed ('\\' = 0x5C)
+  - Netzer returns //0xFF//, successful transfered memory address.
+  - //0x73// initiates a repeated start on the bus.
+  - Netzer returns //0xFF//, successful repeated start.
+  - //0xA1// is the slave address with the R/W bit set, means read access.
+  - Netzer returns //0xFF//, indicating the available slave.
+  - //0xFF// from host: Pull me one byte from slave and acknowledge it.
+  - Netzer returns the value read from memory address 0: //0x55//.
+  - //0x00// from host: Pull me one more byte from slave and stop.
+  - Netzer returns the value read from memory address 1 (auto increment feature of the EEPROM): 0x78.
+  - Netzer automatically announces a stop condition after sending the byte.
+  - Socket sends //0x00// to the host - Frame termination