I2C Error Compendium - Revision history

OlliW at 07:23, 29 July 2017

2017-07-29T07:23:08Z

← Older revision		Revision as of 09:23, 29 July 2017
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	It's like a glass of wine: When it's full, it's full. It doesn't matter whether it was filled with Bordeaux, Chianti, or any other mixture. When the glass contains only a tiny bit of Bordeaux, one can add a lot of Chianti before it overflows, but when the glass is nearly full of Bordeaux, only a tiny amount of Chianti will fit before it reaches the overflow point. So, its not possible to tell how much Chianti is acceptable, since this depends on how much Bordeaux is already in the glass, the only thing that can be determined is that the more Chianti you poor in the glass the more likely it will overflow.		It's like a glass of wine: When it's full, it's full. It doesn't matter whether it was filled with Bordeaux, Chianti, or any other mixture. When the glass contains only a tiny bit of Bordeaux, one can add a lot of Chianti before it overflows, but when the glass is nearly full of Bordeaux, only a tiny amount of Chianti will fit before it reaches the overflow point. So, its not possible to tell how much Chianti is acceptable, since this depends on how much Bordeaux is already in the glass, the only thing that can be determined is that the more Chianti you poor in the glass the more likely it will overflow.

	In the STorM32's GUI, you can find I2C errors ~~recorded~~ in the Data Display window, which can be ~~found~~ by clicking on the {{GUI\|Data Display}} button near the bottom of the GUI.		In the STorM32's GUI, you can find I2C errors displayed in the {{GUI\|Dashboard}} tab, the status bar at the bottom of the main window, or in the Data Display window, which can be opened by clicking on the {{GUI\|Data Display}} button near the bottom of the GUI.

	== Ways to Reduce the I2C Error Rate ==		== Ways to Reduce the I2C Error Rate ==

OlliW: /* Ways to Reduce the I2C Error Rate */

2015-11-15T17:10:17Z

Ways to Reduce the I2C Error Rate

← Older revision		Revision as of 19:10, 15 November 2015
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	* add I2C hardening electronics		* add I2C hardening electronics

	* ditch I2C and use [[STorM32 NT Manuals\|STorM32 NT]]		* ditch I2C and use [[STorM32 NT Manuals\|STorM32 NT]], which would be the ultimative solution

	== Capacitive Load ==		== Capacitive Load ==

OlliW: /* Practical Implications */

2015-11-15T17:09:02Z

Practical Implications

← Older revision		Revision as of 19:09, 15 November 2015
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	The probably most simple approach to avoid I2C errors is to lower the voltage, e.g. to run the controller/motors with 2S instead of 3S. This can be very effective, but can come at the cost of low motor torque, and some STorM32 boards do not run with 2S.		The probably most simple approach to avoid I2C errors is to lower the voltage, e.g. to run the controller/motors with 2S instead of 3S. This can be very effective, but can come at the cost of low motor torque, and some STorM32 boards do not run with 2S.

	The alert reader will have noticed that increasing the current in the I2C lines or decreasing the pullup resistors, respectively, helps to diminish both the effects of the capacitive load and induced voltage disturbances. This in fact helps quite considerably, and it is a good idea to use small pullup resistors, e.g. 1k to 2k on the IMU module. One may wonder why not use really small pullup resistors instead of the typical 2k to 10k range. Well, the answer is that the common I2C drivers are not designed to handle currents larger than a few mA (and this in turn is related to the way in which I2C works). Therefore if very small pullup resistors are used this may damage your electronics. Circuitry exists to create low-impedance I2C communications, but it is not used in our low-budget applications.		The alert reader will have noticed that increasing the current in the I2C lines or decreasing the pullup resistors, respectively, helps to diminish both the effects of the capacitive load and induced voltage disturbances. This in fact helps quite considerably, and it is a good idea to use small pullup resistors, e.g. 1k to 2k on the IMU module. One may wonder why not use really small pullup resistors instead of the typical 2k to 10k range. Well, the answer is that the common I2C drivers are not designed to handle currents larger than a few mA (and this in turn is related to the way in which I2C works). Therefore if very small pullup resistors are used this may damage your electronics. Circuitry exists to create low-impedance I2C communications, which can be added to the I2C wiring and may help significantly, but it is not used in our low-budget applications.

OlliW: /* Ways to Reduce the I2C Error Rate */

2015-11-15T17:06:50Z

Ways to Reduce the I2C Error Rate

← Older revision		Revision as of 19:06, 15 November 2015
Line 30:		Line 30:

	* reduce the I2C pullup resistors on the IMU module		* reduce the I2C pullup resistors on the IMU module

			* add I2C hardening electronics

	* ditch I2C and use [[STorM32 NT Manuals\|STorM32 NT]]		* ditch I2C and use [[STorM32 NT Manuals\|STorM32 NT]]

OlliW: /* Practical Implications */

2015-11-13T10:35:26Z

Practical Implications

← Older revision		Revision as of 12:35, 13 November 2015
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	Ferrite rings are very commonly used to suppress I2C errors. When placed on the motor wires they reduce the slew rate of the motor signals and thereby their ability to induce fault voltages in the I2C lines. When placed on the I2C lines they can compensate, to some degree, the capacitive load and thereby improve the I2C signal quality.		Ferrite rings are very commonly used to suppress I2C errors. When placed on the motor wires they reduce the slew rate of the motor signals and thereby their ability to induce fault voltages in the I2C lines. When placed on the I2C lines they can compensate, to some degree, the capacitive load and thereby improve the I2C signal quality.

			The probably most simple approach to avoid I2C errors is to lower the voltage, e.g. to run the controller/motors with 2S instead of 3S. This can be very effective, but can come at the cost of low motor torque, and some STorM32 boards do not run with 2S.

	The alert reader will have noticed that increasing the current in the I2C lines or decreasing the pullup resistors, respectively, helps to diminish both the effects of the capacitive load and induced voltage disturbances. This in fact helps quite considerably, and it is a good idea to use small pullup resistors, e.g. 1k to 2k on the IMU module. One may wonder why not use really small pullup resistors instead of the typical 2k to 10k range. Well, the answer is that the common I2C drivers are not designed to handle currents larger than a few mA (and this in turn is related to the way in which I2C works). Therefore if very small pullup resistors are used this may damage your electronics. Circuitry exists to create low-impedance I2C communications, but it is not used in our low-budget applications.		The alert reader will have noticed that increasing the current in the I2C lines or decreasing the pullup resistors, respectively, helps to diminish both the effects of the capacitive load and induced voltage disturbances. This in fact helps quite considerably, and it is a good idea to use small pullup resistors, e.g. 1k to 2k on the IMU module. One may wonder why not use really small pullup resistors instead of the typical 2k to 10k range. Well, the answer is that the common I2C drivers are not designed to handle currents larger than a few mA (and this in turn is related to the way in which I2C works). Therefore if very small pullup resistors are used this may damage your electronics. Circuitry exists to create low-impedance I2C communications, but it is not used in our low-budget applications.

OlliW: /* Ways to Reduce the I2C Error Rate */

2015-09-30T09:28:00Z

Ways to Reduce the I2C Error Rate

← Older revision		Revision as of 11:28, 30 September 2015
Line 30:		Line 30:

	* reduce the I2C pullup resistors on the IMU module		* reduce the I2C pullup resistors on the IMU module

			* ditch I2C and use [[STorM32 NT Manuals\|STorM32 NT]]

	== Capacitive Load ==		== Capacitive Load ==

OlliW: /* Ways to Reduce the I2C Error Rate */

2015-08-23T07:14:33Z

Ways to Reduce the I2C Error Rate

← Older revision		Revision as of 09:14, 23 August 2015
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	* increase spacing between I2C cables and motor wires		* increase spacing between I2C cables and motor wires

	* twist the I2C wires; this can ~~take several forms~~, ~~such as~~ twisting all four together, just twisting SCL and SDL, twisting SCL with GND and SDA with VCC etc.		* twist the I2C wires; this can be done in various ways, e.g. twisting all four wires together, just twisting SCL and SDL, twisting SCL with GND and SDA with VCC, etc.

	* shield the I2C wires; using e.g. a coax cable or wrapping the wires with a self adhesive conductive cloth, "EMI shielding"		* shield the I2C wires; using e.g. a coax cable or wrapping the wires with a self adhesive conductive cloth, "EMI shielding" (where the shield must be grounded to be effective)

	* lower the (motor) voltage		* lower the (motor) voltage

OlliW at 08:09, 30 March 2015

2015-03-30T08:09:09Z

← Older revision		Revision as of 10:09, 30 March 2015
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	It's like a glass of wine: When it's full, it's full. It doesn't matter whether it was filled with Bordeaux, Chianti, or any other mixture. When the glass contains only a tiny bit of Bordeaux, one can add a lot of Chianti before it overflows, but when the glass is nearly full of Bordeaux, only a tiny amount of Chianti will fit before it reaches the overflow point. So, its not possible to tell how much Chianti is acceptable, since this depends on how much Bordeaux is already in the glass, the only thing that can be determined is that the more Chianti you poor in the glass the more likely it will overflow.		It's like a glass of wine: When it's full, it's full. It doesn't matter whether it was filled with Bordeaux, Chianti, or any other mixture. When the glass contains only a tiny bit of Bordeaux, one can add a lot of Chianti before it overflows, but when the glass is nearly full of Bordeaux, only a tiny amount of Chianti will fit before it reaches the overflow point. So, its not possible to tell how much Chianti is acceptable, since this depends on how much Bordeaux is already in the glass, the only thing that can be determined is that the more Chianti you poor in the glass the more likely it will overflow.

	~~You~~ can find I2C errors recorded in the "Data Display" window, which can be found by clicking on the "Data Display" button near the bottom of the GUI.		In the STorM32's GUI, you can find I2C errors recorded in the Data Display window, which can be found by clicking on the {{GUI\|Data Display}} button near the bottom of the GUI.

	== Ways to Reduce the I2C Error Rate ==		== Ways to Reduce the I2C Error Rate ==

Katman at 23:39, 29 March 2015

2015-03-29T23:39:19Z

← Older revision		Revision as of 01:39, 30 March 2015
Line 10:		Line 10:

	It's like a glass of wine: When it's full, it's full. It doesn't matter whether it was filled with Bordeaux, Chianti, or any other mixture. When the glass contains only a tiny bit of Bordeaux, one can add a lot of Chianti before it overflows, but when the glass is nearly full of Bordeaux, only a tiny amount of Chianti will fit before it reaches the overflow point. So, its not possible to tell how much Chianti is acceptable, since this depends on how much Bordeaux is already in the glass, the only thing that can be determined is that the more Chianti you poor in the glass the more likely it will overflow.		It's like a glass of wine: When it's full, it's full. It doesn't matter whether it was filled with Bordeaux, Chianti, or any other mixture. When the glass contains only a tiny bit of Bordeaux, one can add a lot of Chianti before it overflows, but when the glass is nearly full of Bordeaux, only a tiny amount of Chianti will fit before it reaches the overflow point. So, its not possible to tell how much Chianti is acceptable, since this depends on how much Bordeaux is already in the glass, the only thing that can be determined is that the more Chianti you poor in the glass the more likely it will overflow.

			You can find I2C errors recorded in the "Data Display" window, which can be found by clicking on the "Data Display" button near the bottom of the GUI.

	== Ways to Reduce the I2C Error Rate ==		== Ways to Reduce the I2C Error Rate ==

OlliW at 08:10, 13 January 2015

2015-01-13T08:10:22Z

← Older revision		Revision as of 10:10, 13 January 2015
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	<span style="font-size:88%">''by OlliW, with edits by ~~bruce356~~</span>''		<span style="font-size:88%">''by OlliW, with edits by Bruce356</span>''

	I2C errors are probably the most annoying side effect of the technology we are using in our brushless gimbals.		I2C errors are probably the most annoying side effect of the technology we are using in our brushless gimbals.
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	* induced signal disturbances due to capacitive coupling to outside fields		* induced signal disturbances due to capacitive coupling to outside fields

	Importantly, all error sources add up. One therefore can't give decisive threshold values, for example, the length of the I2C wires should not be more than 40 cm long. Without any further error sources one might be able to use much longer wires, but if motor wires are too close to the IMU cabling then shorter wires might be required.		Importantly, all error sources add up. One therefore can't give decisive threshold values, for example, the length of the I2C wires should not be more than 40 cm long. Without any further error sources one might be able to use much longer wires, but if motor wires are too close to the IMU cabling then shorter wires might be required.

	It's like a glass of wine: When it's full, it's full. It doesn't matter whether it was filled with Bordeaux, Chianti, or any other mixture. When the glass contains only a tiny bit of Bordeaux, one can add a lot of Chianti before it overflows, but when the glass is nearly full of Bordeaux, only a tiny amount of Chianti will fit before it reaches the ~~overflows~~ point. So, its not possible to tell how much Chianti is acceptable, since this depends on how much Bordeaux is already in the glass, the only thing that can be determined is that the more Chianti you poor in the glass the more likely it will overflow.		It's like a glass of wine: When it's full, it's full. It doesn't matter whether it was filled with Bordeaux, Chianti, or any other mixture. When the glass contains only a tiny bit of Bordeaux, one can add a lot of Chianti before it overflows, but when the glass is nearly full of Bordeaux, only a tiny amount of Chianti will fit before it reaches the overflow point. So, its not possible to tell how much Chianti is acceptable, since this depends on how much Bordeaux is already in the glass, the only thing that can be determined is that the more Chianti you poor in the glass the more likely it will overflow.

	== Ways to Reduce the I2C Error Rate ==		== Ways to Reduce the I2C Error Rate ==

	Before looking at the I2C errors, here is a brief summary to help reduce problems with the ~~error-prone~~ I2C connection to an IMU module:		Before looking at the I2C errors, here is a brief summary of methods, which help reduce problems with the I2C connection to an IMU module:

	* reduce length of ~~cable~~		* reduce length of I2C cables

	* increase spacing between I2C cables and motor wires		* increase spacing between I2C cables and motor wires

	* twist ~~all~~ wires ~~where possible including the IMU cable(reduces Electromagnetic interference)~~; ~~for the IMU~~ this can take several forms, such as twisting all four together, just twisting SCL and SDL, twisting SCL with GND and SDA with VCC etc.		* twist the I2C wires; this can take several forms, such as twisting all four together, just twisting SCL and SDL, twisting SCL with GND and SDA with VCC etc.

	* shield the wires; using e.g. a coax cable or wrapping the wires with a self adhesive conductive cloth, "EMI shielding"		* shield the I2C wires; using e.g. a coax cable or wrapping the wires with a self adhesive conductive cloth, "EMI shielding"

	* lower the (motor) voltage		* lower the (motor) voltage
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	* add ferrite rings; these can be fitted in various ways, such as, putting the rings on the I2C wires and/or the motor wires, they can be fitted at either ends of the wires.		* add ferrite rings; these can be fitted in various ways, such as, putting the rings on the I2C wires and/or the motor wires, they can be fitted at either ends of the wires.

	* reduce the I2C pullup resistors on the IMU module ~~e.g. to 1k~~		* reduce the I2C pullup resistors on the IMU module

	== Capacitive Load ==		== Capacitive Load ==
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	Capacitive load arises from the cables themselves, and the longer the cables are the higher the capacitive load becomes.		Capacitive load arises from the cables themselves, and the longer the cables are the higher the capacitive load becomes.

	Therefore, for any I2C system there is an "intrinsic" maximum length up to which the I2C communication will work. In practice this maximum length is not achieved, since, as mentioned in the introduction, other I2C error sources may be present reducing the practical length. The capacitive load ~~of the IMU cable~~ depends also on the type of cable. Thin wires for instance have a smaller capacity than thicker wires. In practice, however, there is usually little room to play with this factor.		Therefore, for any I2C system there is an "intrinsic" maximum length up to which the I2C communication will work. In practice this maximum length is not achieved, since, as mentioned in the introduction, other I2C error sources may be present reducing the practical length. The capacitive load depends also on the used type of cable. Thin wires for instance have a smaller capacity than thicker wires. In practice, however, there is usually little room to play with this factor.

	Capacitive load also arises from anything conducting in the near surrounding area of the I2C clock and/or data wires.		Capacitive load also arises from anything conducting in the near surrounding area of the I2C clock and/or data wires.

	This is indeed a major factor, and - fortunately - it is to a high degree under our control. The possible contributors falling into this category are very diverse; they range from things like spacing between the wires themselves or to GND or Vcc, shielding such as in coax wires, twisted or non-twisted wires and the manner in which they are twisted, conducting areas like metal bars or carbon plates to which the IMU module is mounted or the cables are fixed to~~, connectors~~, and so on. It is as it was mentioned, it can arise from '''''anything''''' that is conducting in the surrounding area. Fortunately, the rules which determine the value for capacitance are well known. In a nutshell, the larger the conducting area the larger the capacitance, and the further the distance from the conducting area the smaller the capacitance. This immediately gives us the necessary rules to control, and possibly avoid the problem.		This is indeed a major factor, and - fortunately - it is to a high degree under our control. The possible contributors falling into this category are very diverse; they range from things like spacing between the wires themselves or to GND or Vcc, shielding such as in coax wires, twisted or non-twisted wires and the manner in which they are twisted, conducting areas like metal bars or carbon plates to which the IMU module is mounted or the I2C cables are fixed to, and so on. It is as it was mentioned, it can arise from '''''anything''''' that is conducting in the surrounding area. Fortunately, the rules which determine the value for capacitance are well known. In a nutshell, the larger the conducting area the larger the capacitance, and the further the distance from the conducting area the smaller the capacitance. This immediately gives us the necessary rules to control, and possibly avoid the problem.

	The acceptable capacitive load, from both the cables and the surrounding ~~EMI~~, depends on additional factors, such as the current capabilities of the I2C drivers and the pullup resistors.		The acceptable capacitive load, from both the cables and the conducting surrounding areas, depends on additional factors, such as the current capabilities of the I2C drivers and the pullup resistors.

	== Induced Signal Disturbances ==		== Induced Signal Disturbances ==

	Wires in close proximity to the I2C clock and data lines may, due to capacitive coupling, induce fault voltages in I2C lines and thus disrupt the I2C signals. This again may prevent the electronics from detecting the I2C signals correctly and ~~therefore may~~ bring it into an unexpected state causing I2C errors to occur. The I2C errors due to induced disturbances are often fatal in the sense that it can be difficult for the electronics to recover from these errors.		Wires in close proximity to the I2C clock and data lines may, due to capacitive coupling, induce fault voltages in the I2C lines and thus disrupt the I2C signals. This again may prevent the electronics from detecting the I2C signals correctly and even bring it into an unexpected state, therefore causing I2C errors to occur. The I2C errors due to induced disturbances are often fatal in the sense that it can be difficult for the electronics to recover from these errors.

	For our gimbals, the primary origin of these interferences are from the motor wires. The motor wires carry high voltage signals, high in comparison to the circa 3 volts of the I2C signals, ~~the motor wires~~ are ~~also~~ pulsed with large slew rates. When ~~these signals~~ come close to the I2C lines, ~~the motor wires~~ can easily disturb the signals on the I2C lines.		For our gimbals, the primary origin of these interferences are from the motor wires. The motor wires carry high voltage signals, high in comparison to the circa 3 volts of the I2C signals, which in addition are pulsed with large slew rates. When the motor wires come close to the I2C lines, they can easily disturb the signals on the I2C lines.

	The strength of the induced disturbances depends on some additional factors, such as the current capabilities of the I2C drivers and the pullup resistors.		The strength of the induced disturbances depends on some additional factors, such as the current capabilities of the I2C drivers and the pullup resistors.
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	Ferrite rings are very commonly used to suppress I2C errors. When placed on the motor wires they reduce the slew rate of the motor signals and thereby their ability to induce fault voltages in the I2C lines. When placed on the I2C lines they can compensate, to some degree, the capacitive load and thereby improve the I2C signal quality.		Ferrite rings are very commonly used to suppress I2C errors. When placed on the motor wires they reduce the slew rate of the motor signals and thereby their ability to induce fault voltages in the I2C lines. When placed on the I2C lines they can compensate, to some degree, the capacitive load and thereby improve the I2C signal quality.

	The alert reader will have noticed that increasing the current in the I2C lines or decreasing the pullup resistors, respectively, helps to diminish both the effects of the capacitive load and induced voltage disturbances. This in fact helps quite considerably, and it is ~~also~~ a good idea to use small pullup resistors. One may wonder why not use really small pullup resistors instead of the typical 1k to 10k range. Well, the answer is that the ~~current standard~~ I2C drivers are not designed to handle currents larger than a few mA (and this in turn is ~~also~~ related to the way in which I2C works). Therefore if very small pullup resistors are used this may damage your electronics. Circuitry exists to create low-impedance I2C communications, but it is not used in our low-budget applications.		The alert reader will have noticed that increasing the current in the I2C lines or decreasing the pullup resistors, respectively, helps to diminish both the effects of the capacitive load and induced voltage disturbances. This in fact helps quite considerably, and it is a good idea to use small pullup resistors, e.g. 1k to 2k on the IMU module. One may wonder why not use really small pullup resistors instead of the typical 2k to 10k range. Well, the answer is that the common I2C drivers are not designed to handle currents larger than a few mA (and this in turn is related to the way in which I2C works). Therefore if very small pullup resistors are used this may damage your electronics. Circuitry exists to create low-impedance I2C communications, but it is not used in our low-budget applications.