Uploaded February 2025 | Updated September 2026, 1 hour ago
With demonstrations using Arduinos and TI SN75176B transceivers …
↓↓↓ Complete description, time index and links below ↓↓↓
In the last video we’ve introduced addressing to handle more than one slave on the bus and timeouts to bulletproof our communication against unresponsive slaves (link below). But there’s still a potential source of error. Let’s fix that now.
First we have a look at the problem and the solution for it – failsafe biasing. Then we go through all the details and upgrade our hardware accordingly – with two more resistors. Finally, failsafe biasing allows us to greatly simplify our protocol.
00:00 Intro – removing source of error and simplifying protocol
00:53 Problem – receivers listening with no transmitter enabled
03:04 Solution – biasing the bus to above the threshold voltage
06:21 Assumptions – idle voltage, supply voltage, bus load
09:11 Bus Load – receivers as resistor plus termination resistors
12:07 Failsafe Resistors – failsafe current and voltage accross
13:28 Termination Resistors – one has to be recalculated
16:03 Failsafe Load – of failsafe resistors on the bus is significant
18:49 Placement – at one end or both ends of the bus
20:40 Demonstration I – the bus is now always in a defined state
22:29 Failsafe Receivers – are an alternative to failsafe biasing
24:28 Protocol – new version is simpler and saves one MCU pin
28:23 Code – for master and slave is also greatly simplified
32:31 Demonstration II – less action and more throughput
34:28 Wrap-up – next we tackle the full-duplex RS-485 bus, bye
Tutorials youtube.com/playlist?list=PLwq-2MnM58FKn3920rc1V0qoTsQDheTIw
RS-485 – The Basics (1/2): Principles, Topology, Specification, Performance youtu.be/DRR9NUAMKic
RS-485 – The Basics (2/2): Simple Master-Slave Half-Duplex Setup youtu.be/FBA98ks61Dg
RS-485 – The Details (1/4): Timeouts, Addressing, Multiple Slaves youtu.be/ncQ16ht-9nU
RS-485 – The Details (2/4): Failsafe Biasing, Associated Protocol Simplifications youtu.be/ITlgIUTyPVo
RS-485 – The Details (3/4): Full-Duplex Bus, Interleaving Messages youtu.be/N9N53I6ipG0
RS-485 – The Details (4/4): Modbus, PROFIBUS, DMX youtu.be/SzlGJrPhmwE
RS-422 Differential Signaling (Renesas ISL8490, Arduino MCU) – The Basics (1/2) youtu.be/6YWZMRe-7DQ
RS-422 Differential Signaling (Renesas ISL8490, Arduino MCU) – The Basics (2/2) youtu.be/hoZ4D2Tk9Qc
RS-422 Differential Signaling (ISL8490, AdUM121N) – The Details (1/2) youtu.be/__EvQgr3sGA
RS-422 Differential Signaling (ISL8490, AdUM121N) – The Details (2/3) youtu.be/0WHKMjBg1QQ
RS-422 Differential Signaling (ISL8490, AdUM121N) – The Details (3/4) youtu.be/y0wD84uRvbY
RS-422 Differential Signaling (ISL8490, AdUM121N) – The Details (4/4) youtu.be/Xamy60ZRohw
My Code drive.google.com/drive/folders/11rs-fVaGd1o7osX7Kb3Id6G8_kFdO4QJ?usp=sharing
STMicroelectronics, Application Note AN1690, Fail-safe biasing for ST485EB st.com/resource/en/application_note/an1690-failsafe-biasing-for-st485eb-stmicroelectronics.pdf
Texas Instruments, RS-485: Passive failsafe for an idle bus ti.com/lit/pdf/slyt324
Texas Instruments, Application Report, RS-422 and RS-485 Standards Overview and System Configurations focus.ti.com/lit/an/slla070d/slla070d.pdf
#rs485 #arduino #mcu #microcontroller #tutorials #tutorial #how-to #robertssmorgasbord
With demonstrations using Arduinos and TI SN75176B transceivers …
↓↓↓ Complete description, time index and links below ↓↓↓
In the last video we’ve introduced addressing to handle more than one slave on the bus and timeouts to bulletproof our communication against unresponsive slaves (link below). But there’s still a potential source of error. Let’s fix that now.
First we have a look at the problem and the solution for it – failsafe biasing. Then we go through all the details and upgrade our hardware accordingly – with two more resistors. Finally, failsafe biasing allows us to greatly simplify our protocol.
00:00 Intro – removing source of error and simplifying protocol
00:53 Problem – receivers listening with no transmitter enabled
03:04 Solution – biasing the bus to above the threshold voltage
06:21 Assumptions – idle voltage, supply voltage, bus load
09:11 Bus Load – receivers as resistor plus termination resistors
12:07 Failsafe Resistors – failsafe current and voltage accross
13:28 Termination Resistors – one has to be recalculated
16:03 Failsafe Load – of failsafe resistors on the bus is significant
18:49 Placement – at one end or both ends of the bus
20:40 Demonstration I – the bus is now always in a defined state
22:29 Failsafe Receivers – are an alternative to failsafe biasing
24:28 Protocol – new version is simpler and saves one MCU pin
28:23 Code – for master and slave is also greatly simplified
32:31 Demonstration II – less action and more throughput
34:28 Wrap-up – next we tackle the full-duplex RS-485 bus, bye
Tutorials youtube.com/playlist?list=PLwq-2MnM58FKn3920rc1V0qoTsQDheTIw
RS-485 – The Basics (1/2): Principles, Topology, Specification, Performance youtu.be/DRR9NUAMKic
RS-485 – The Basics (2/2): Simple Master-Slave Half-Duplex Setup youtu.be/FBA98ks61Dg
RS-485 – The Details (1/4): Timeouts, Addressing, Multiple Slaves youtu.be/ncQ16ht-9nU
RS-485 – The Details (2/4): Failsafe Biasing, Associated Protocol Simplifications youtu.be/ITlgIUTyPVo
RS-485 – The Details (3/4): Full-Duplex Bus, Interleaving Messages youtu.be/N9N53I6ipG0
RS-485 – The Details (4/4): Modbus, PROFIBUS, DMX youtu.be/SzlGJrPhmwE
RS-422 Differential Signaling (Renesas ISL8490, Arduino MCU) – The Basics (1/2) youtu.be/6YWZMRe-7DQ
RS-422 Differential Signaling (Renesas ISL8490, Arduino MCU) – The Basics (2/2) youtu.be/hoZ4D2Tk9Qc
RS-422 Differential Signaling (ISL8490, AdUM121N) – The Details (1/2) youtu.be/__EvQgr3sGA
RS-422 Differential Signaling (ISL8490, AdUM121N) – The Details (2/3) youtu.be/0WHKMjBg1QQ
RS-422 Differential Signaling (ISL8490, AdUM121N) – The Details (3/4) youtu.be/y0wD84uRvbY
RS-422 Differential Signaling (ISL8490, AdUM121N) – The Details (4/4) youtu.be/Xamy60ZRohw
My Code drive.google.com/drive/folders/11rs-fVaGd1o7osX7Kb3Id6G8_kFdO4QJ?usp=sharing
STMicroelectronics, Application Note AN1690, Fail-safe biasing for ST485EB st.com/resource/en/application_note/an1690-failsafe-biasing-for-st485eb-stmicroelectronics.pdf
Texas Instruments, RS-485: Passive failsafe for an idle bus ti.com/lit/pdf/slyt324
Texas Instruments, Application Report, RS-422 and RS-485 Standards Overview and System Configurations focus.ti.com/lit/an/slla070d/slla070d.pdf
#rs485 #arduino #mcu #microcontroller #tutorials #tutorial #how-to #robertssmorgasbord
