In the first part of this series, we took a closer look at the basics of LIN networking, the key parameters for a two-wire LIN (Atmel) solution and the details of a LIN Bus power supply. In the second part of this series, we discussed various aspects of slave node current consumption, specifically, system clock frequency, sleep mode power management and LIN scheduling power management.
And today we’re going to talk about slave node buffer capacitance, LIN Bus data protocol and a multi-slave evaluation network.
“While an important piece of the two-wire LIN equation, sizing of the slave node buffer capacitor, CVS_S, is not a dominant factor. The capacitor must provide sufficient charge reserve to power the slave node during a LIN frame data packet (LIN signal is periodically asserted low) and also receive a full charge between LIN frame data transmissions (the LIN signal is pulled up to system supply voltage),” Atmel engineering rep Darius Rydahl told Bits & Pieces.
“In practice, bench tests indicate that a buffer capacitor of 47μF to 100μF is sufficient to maintain power to the slave node for a network operating at a data rate of 19.2kbaud with a 100ms delay (or greater) between LIN data frames and a 9V minimum operating battery voltage.”
In terms of the LIN Bus Data Protocol, Rydahl notes that the format of the LIN bus data protocol will affect the charge/discharge rate of the slave node supply line buffer capacitor. Three (primary) factors affect the data format: Rate of data transfer, quantity of data transferred and LIN data schedule table period.
- Microchip Studio is an Integrated Development Platform (IDP) for developing and debugging AVR ® and SAM microcontroller applications. It merges all of the great features and functionality of Atmel Studio into Microchip’s well-supported portfolio of development tools to give you a seamless and easy-to-use environment for writing, building and debugging your applications written in C/C.
- In this guide we introduce the Local Interconnect Network (LIN) protocol basics incl. CAN, use cases, how LIN works and the six LIN frame types. Note: This is a practical intro so we will also look at the basics of LIN bus data logging. Learn more below!
Ethernet can be used in many communications, consumer, industrial, automotive and other applications that require network connectivity, including remote monitoring of systems, implementing precision industrial motor control and communicating with Internet of Things (IoT) devices. Windows 7 Windows 8 Windows 10 Language: EN Version: 10.0.0.303. Free OS: Windows 7 Language: EN Version: A01. Acer Aspire One AO752 Wireless Network Driver. Download the Wireless Network driver for the Acer Aspire One. License: Free OS: Windows 7. Download the Network card driver for your Compaq CQ10-400 Mini PC Series.
“The LIN bus data rate should be kept high, i.e., a maximum baud rate of 19.2kHz or higher to maximize the speed at which the data can be transferred. The quantity of data number of bits) should be kept as low as possible in order to minimize the duration of the dominant state (logic level low) on the LIN bus line,” he continued.
“And finally, the LIN schedule table period should be long enough in duration to allow the LIN bus powered slave node time to fully recharge the buffer capacitor, CVS_S, between LIN message frames. It should also be noted that most Atmel LIN transceivers are capable of baud rates in excess of the LIN specification.”
On the multi-slave evaluation network side, the two-wire LIN network used for test and characterization purposes is illustrated in figure 8. Essentially, the two-wire LIN network total node count is limited only by the LIN master pull-up resistor’s ability to source the required current to the attached slave nodes to maintain normal operation (slave node VS greater than 5.5V).
“Each node has been configured using the Atmel ATA6617-EK evaluation board (SiP: AVR MCU, ATtiny167 and Atmel SBC ATA6624),” said Rydahl. “This configuration provides one possible operating scenario and, as such, will most likely need to be modified to accommodate the end user’s application.”
The network utilizes the standard LIN protocol and does not deviate from the LIN2.x standard in any manner. The schedule table has been optimized for the two-wire LIN application where a LIN wake-up frame is followed by a single slave node frame shown in figure 9.
“Standard LIN protocol dictates that each node must process every incoming frame ID message on the bus. This forces each slave node to wake-up on every incoming message, regardless of ownership. Sending a wake-up frame followed by a single slave node frame minimizes the time that each slave node is powered ON,” he added.
“The alternate approach of sending a wake-up frame followed by a sequential burst of all the slave frames will cause slave nodes to remain awake longer than necessary. The end result is an overall increase in system load current—a scenario that should be avoided.”
Interested in learning more about Two-Wire LIN networking with Atmel? Be sure to check out part one and two of this series. Part four will run tomorrow.
Atmel Network & Wireless Cards Driver Download For Windows 10 32-bit
Current-gen vehicles are packed with hundreds of sensors used to monitor and display parameters such as temperature and pressure. In most instances, these sensors are remotely located within a vehicle far away from the host microcontroller (MCU) responsible for monitoring and processing the sensor data.
As such, these sensors typically do not directly connect to a network (such as CAN or LIN) due to the vehicle wiring overhead associated with connecting to the network. One such method for overcoming this wiring limitation is to convert the standard three-wire LIN network to a two-wire implementation where the LIN slave nodes harvest power directly from the LIN bus master communication wire, thereby eliminating the need for an individual battery supply wire to each slave node.
As Atmel engineering rep Darius Rydahl notes, a standard LIN bus consists of a master node and up to 15 slave nodes connected to a single network. The physical LIN network is a three-wire configuration consisting of power (vehicle battery), ground and the LIN bus communication line. A pull-up resistor, RLIN, typically 1kΩ, is required on the master’s LIN bus line. Under normal LIN bus operation, this pull-up resistor provides a voltage bias on the LIN bus line to the slave nodes on the LIN network. It does not power the LIN slave nodes, rather slave node power is derived from the battery input to the device, as shown in Figure 1.
“It is possible to use a non-standard LIN network architecture that simplifies to two wires. This approach relies on the harvesting of power by a connected slave node directly from the LIN bus line, thus eliminating the need for an independent slave node battery supply line (see figure 2),” Rydahl told Bits & Pieces. “With the battery supply line removed, all that is required to power the slave node is a blocking diode, VDS and buffer capacitor, CVS_S, large enough to sustain the slave node supply voltage during the transmission of LIN data packets, which periodically pulls the LIN signal to ground.”
In this series, Bits & Pieces will outline the implementation of this two-wire approach and identify the inherent system-level tradeoffs that must be considered to fully realize a functional two-wire LIN network.
According to Rydahl, the key to successfully implementing a two-wire LIN network centers around the power requirements of the connected slave node. Simply put, the slave node must be supplied with sufficient power to maintain communication at the minimum system operating voltage: typically 9V. If this condition cannot be met, it is unlikely that the two-wire LIN implementation will be a viable solution. Key parameters that affect the slave node’s performance in a two-wire implementation include LIN bus power supply, slave node current consumption, slave node buffer capacitance and LIN Bus data protocol.
“In terms of the LIN Bus power supply, the two-wire LIN network is limited by the power supplied from the master to the slave node over the LIN bus line. Meaning, the supply to the LIN slave in this configuration will be dictated by the LIN bus master pull-up resistor, RLIN (see figure 2),” Rydahl continued. “The slave node has a fixed minimum input voltage operating requirement of 5.5V (reference: the Atmel ATA6624 LIN transceiver). In order to meet this minimum operating voltage requirement, the load current drawn by the slave node must not cause the voltage drop across the LIN master pull-up resistor to increase to the point at which the input voltage to the slave node drops below 5.5V.”
Atmel Network & Wireless Cards Driver Download For Windows 10 64-bit
As Rydahl points out, this is the minimum operating voltage threshold for slave node voltage regulator operation. Indeed, figure 3 shows the maximum load current available to the slave node at the minimum supply voltage of 5.5V at different LIN master pull-up resistances.
“The 1kΩ master pull-up resistor specified in the LIN standard specification cannot be used in the two-wire configuration. The resistor is too large and, as a result, is unable to properly source the slave node load,” he said. “As such, the pull-up resistor must be reduced in size to the smallest value possible without exceeding the current limitation specification of the LIN driver. In the case of the typical Atmel LIN transceiver, the ATA6624, the recommended minimum pullup resistor value is 220Ω. Resistances lower than this could result in excessive current flow through the LIN transceiver when the LIN bus is asserted low.”
Atmel Network & Wireless Cards Driver Download For Windows 10 7
Interested in learning more about Two-Wire LIN networking with Atmel? Be sure to check out part two of this series here.