Embedded Systems · Cluster
Embedded Buses
I2C, SPI, CAN, and their failure modes.
- 01 Open-Drain Signalling and Arbitration on a Shared Two-Wire Bus How pull-up resistors and open-drain drivers turn two wires into a wired-AND, and why that makes simultaneous transmission by two masters harmless rather than destructive.
- 02 The Shift Register Behind SPI and Why There Are Four Clock Modes Two shift registers joined by two wires explain SPI completely, including the CPOL and CPHA combinations, the daisy chain, and the consequences of having no acknowledgement.
- 03 UART Framing, Baud Rate Error, and the Overrun That Loses Data How start-bit synchronisation survives clock mismatch, how much baud error a ten-bit frame tolerates, and why the receive FIFO overruns before the interrupt handler runs.
- 04 CAN Frame Layout and Why Bit Stuffing Is Mandatory The field-by-field structure of a classical CAN frame, the stuff-bit rule that keeps receivers synchronised, and what each field costs in the worst case.
- 05 Clock Stretching and Recovering a Bus Held Low by a Stuck Slave Why a slave is allowed to hold the clock line down, how that interacts with arbitration and timeouts, and the pulse sequence that frees a device stuck mid-byte.
- 06 Differential Signalling, Common-Mode Rejection, and Where to Put the Terminator Why a twisted pair driven in opposition rejects ground noise, how termination absorbs reflections, and why the correct value is set by the cable rather than the transceiver.
- 07 CAN Error Counters and the State Machine That Silences a Faulty Node Transmit and receive error counters move by different amounts for different faults, and the three-state model that follows from them decides when a node stops talking.
- 08 Sizing Pull-Up Resistors Against Bus Capacitance and Rise Time The two inequalities that bound a pull-up value: the rise time the mode allows and the sink current a device guarantees, and why the window closes as the bus gets faster.
- 09 CAN FD: Longer Payloads, a Faster Data Phase, and the Loop That Must Close in Time The frame format changes that let a CAN FD frame carry 64 bytes at a higher bit rate, and the transceiver symmetry requirement that limits how far the data phase can be pushed.
- 10 Worst-Case Response Time of a CAN Message Under Fixed-Priority Arbitration Why the identifier is a priority, how the blocking and interference terms of a response-time bound are computed for a bit-stuffed frame, and where the analysis stops being optimistic.