STM32G4

[rleh]

STM32G4 u(s)art has no tcbgt

For the STM32G4 series only USART1/2/3 support TCBGT, UART4/5 and LPUART do not support it.

[salkinium]

You should check all of them with care, I did this best-effort only!

[salkinium]

Ready for merging? Or do you have more fixes?

[rleh]

I don't know what tcbgt means. It was introduced here: modm-io/modm@6cc4ac4316 Can you explain that?

I removed it because it fixed compilation errors.

Currently the modm-io/modm#287 builds successfully on CircleCI without this changes merged.

[salkinium]

The "tcbgt" feature refers to the availablility of the TCBGT bit in the USART_ ISR registers:

• Bit 25 TCBGT: Transmission complete before guard time flag

The feature descriptions in modm-devices only operate on a comparison of register maps, so that compatible subsets of one larger map can be distiguished. The SPI driver in modm uses this info much better than the UART driver.

[rleh]

STM32G4 Reference Manual (RM0440 Rev 1)

36.7.9 USART interrupt and status register [alternate] (USART_ISR)

• Bit 25 TCBGT: Transmission complete before guard time flag
  • This bit is set when the last data written in the USART_TDR has been transmitted correctly out of the shift register. It is set by hardware in Smartcard mode, if the transmission of a frame containing data is complete and if the smartcard did not send back any NACK. An interrupt is generated if TCBGTIE=1 in the USART_CR3 register. This bit is cleared by software, by writing 1 to the TCBGTCF in the USART_ICR register or by a write to the USART_TDR register.
    • 0: Transmission is not complete or transmission is complete unsuccessfully (i.e. a NACK is received from the card)
    • 1: Transmission is complete successfully (before Guard time completion and there is no NACK from the smart card).
  • Note: If the USART does not support the Smartcard mode, this bit is reserved and kept at reset value. If the USART supports the Smartcard mode and the Smartcard mode is enabled, the TCBGT reset value is ‘1’. Refer to Section 36.4: USART implementation on page 1554.

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[salkinium]

Ugh. #7 is coming to get me. All this data needs to become an order of magnitude better and there needs to be unit tests (or assumption tests) built into this repo.

[salkinium]

This can be closed, right?

[rleh]

Only UART1/2/3 have the TCBGT feature. This is currentyl not representable in modm-devices, see #7.