I have a STM32F303 connected to a L9616 as displayed below.
The pullup resistor R3 is not present any more. Please ignore it.
Vdd is 3.3V but, as can be seen, I have set Vs to 5V, believing that was necessary to make the CAN BUS work.
With an oscilloscope channel connected between CAN_BUS_H and GND I can see a Tx pulse train, but STM32 HAL reports state 2 and error 43 (0x2B) after transmission. If I understood well, this means 0x20 + 0x10 + 0x1 which leads me to believe that the following three errors are occurring:
#define HAL_CAN_ERROR_EWG (0x00000001U) /*!< Protocol Error Warning */
#define HAL_CAN_ERROR_FOR (0x00000010U) /*!< Form error */
#define HAL_CAN_ERROR_ACK (0x00000020U) /*!< Acknowledgment error
Besides that reported error, the most annoying fact is that I tried many ways to fire the Rx Callbacks on another node with similar configurations, without success.
When investigating the problem I measured, on the reception node, CAN_TX at 3.3V and CAN_RX at 5V. I believe this 5V at CAN RX is, somehow, blinding STM32 from the Rx transceiver signal.
Can you help me with some information? Or could you please share a proved working connection diagram between STM32 and L9616 with me?
Best regards,
Hering
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Accepted Solutions
Hello,
I don't see an issue in the schematics but I have some questions:
- How you did connect ASC pin? (the status of JP1).
- Did you fit JP2 jumper to connect the termination resistor to the bus?
- Is there another node connected to the bus that interacts with your node? If not, you have to connect another node having the same CAN bitrate.
- What is the clock source you are using HSE with an external crystal or HSI?
- Could you please provide your CAN bitrate configuration? CAN prescaler, BS1 and BS2? If you can share your code.
Besides that, I see another issue with the transceiver L9616 which is a 5V transceiver.
According to its datasheet VTXO min is 0.7 x Vs. In your case Vs = 5V -> So VTXO min = 0.7 x 5 = 3.5V that needs to be seen from the STM32. In your case, the latter is supplied by 3.3V and the GPIOs cannot deliver more than VDD = 3.3V. So it's out of spec of the transceiver. You need to supply your transceiver with maximum 4.71V (3.3/0.7) to be in the transceiver's spec.
Hello,
I don't see an issue in the schematics but I have some questions:
- How you did connect ASC pin? (the status of JP1).
- Did you fit JP2 jumper to connect the termination resistor to the bus?
- Is there another node connected to the bus that interacts with your node? If not, you have to connect another node having the same CAN bitrate.
- What is the clock source you are using HSE with an external crystal or HSI?
- Could you please provide your CAN bitrate configuration? CAN prescaler, BS1 and BS2? If you can share your code.
Besides that, I see another issue with the transceiver L9616 which is a 5V transceiver.
According to its datasheet VTXO min is 0.7 x Vs. In your case Vs = 5V -> So VTXO min = 0.7 x 5 = 3.5V that needs to be seen from the STM32. In your case, the latter is supplied by 3.3V and the GPIOs cannot deliver more than VDD = 3.3V. So it's out of spec of the transceiver. You need to supply your transceiver with maximum 4.71V (3.3/0.7) to be in the transceiver's spec.
Thanks a lot for your answer, @SofLit
I provide answers for your questions below.
- How you did connect ASC pin? (the status of JP1).
Currently it is floating. I tried both JP1 possibilities with an external jumper, but saw no noticeable differences in the pulse train on the oscilloscope screen, so I disregarded it. Should I set it in the high bandwidth option (GND)?
- Did you fit JP2 jumper to connect the termination resistor to the bus?
The jumper is fitted, but the resistor is not connected. I have placed two 120 ohm resistors in the bus endings instead. The bus is a vertical PCB which connects the modules.
- Is there another node connected to the bus that interacts with your node? If not, you have to connect another node having the same CAN bitrate.
Yes, there is. Same settings.
- What is the clock source you are using HSE with an external crystal or HSI?
External crystal, 16MHz.
- Could you please provide your CAN bitrate configuration? CAN prescaler, BS1 and BS2? If you can share your code.
Sure:
hcan.Instance = CAN;
hcan.Init.Prescaler = 2;
hcan.Init.Mode = CAN_MODE_NORMAL;
hcan.Init.SyncJumpWidth = CAN_SJW_1TQ;
hcan.Init.TimeSeg1 = CAN_BS1_5TQ;
hcan.Init.TimeSeg2 = CAN_BS2_5TQ;
hcan.Init.TimeTriggeredMode = DISABLE;
hcan.Init.AutoBusOff = ENABLE;
hcan.Init.AutoWakeUp = ENABLE;
hcan.Init.AutoRetransmission = DISABLE;
hcan.Init.ReceiveFifoLocked = DISABLE;
hcan.Init.TransmitFifoPriority = DISABLE;
Again, thank you for your help.
Thank you for these information.
Could you please share your system clock config?
By this statement: "With an oscilloscope channel connected between CAN_BUS_H and GND I can see a Tx pulse train" : do you mean that you are seeing CAN frame transmitted by STM32 or from another node?
What about CAN_BUS_L? Are you seeing an expected signal?
Regarding ASC pin and according to L9616 datasheet, the pin is pulled down to GND through an internal resistor:
I think no need to connect it for the moment. In this configuration you are in High speed config > 250kb/s
Regarding your last question about a transceiver replacement and since your HW is already fixed, I would suggest MCP2561 which is pin to pin compatible with L9616 (unfortunately there is no replacement from ST):
According to its datasheet this transceiver fit exactly your needs. Power supply = 5V and VIH min = 2V < 3.3V
Hello again,
I tried to simulate your config and found that you have a non-common CAN bitrate:
This is your system clock config:
Could you please confirm?
Regarding MCP2561 has STBY pin which consists of putting the transceiver in standby mode. In that case you couldn't transmit/receive any CAN frame. There is an internal pull up resistor connected to that pin (by default standby mode activated). So you need to at least pull STBY pin to the ground.
