There are 4/2 USART/UART ports in STM32F407 (Page 15) MCUs as shown in the image. I need 4 UART ports in an application. I wonder if its possible to use 2+2 (UASRT+UART) ports for my purpose in this MCU?enter image description here


Included link to the datasheet. Page 15

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    \$\begingroup\$ The table seems to be pretty clear...4 USARTs or 2 UARTs. Maybe you should provide a link to the relevant documentation. \$\endgroup\$ – Elliot Alderson Feb 19 '19 at 23:20
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    \$\begingroup\$ I think that's just inconsistent labeling on ST's part. Because USART/UART 4/2 means 4 USARTs AND 2 UARTs, whereas SPI/I2S actually means 3 SPIs two of which can be configured as I2S. In datasheets for other STM32s, UART and USART modules are listed separately, but SPI and I2S modules are listed together. If the OP looks in another part of the datasheet he should find a table that lists the features of every USART/UART module, among which is a "synchronous" feature which some will have and others will not. \$\endgroup\$ – DKNguyen Feb 19 '19 at 23:28
  • \$\begingroup\$ Edit: Included link to the datasheet. \$\endgroup\$ – scico111 Feb 19 '19 at 23:34
  • \$\begingroup\$ I take it back. Whoever wrote this particular datasheet didn't even include the important features into the USART feature table (Table 5). They just lumped it all under "standard features". Since they all share the same section in the User Reference Manual, the only way to tell if a module is capable of synchronous operation is to see if it has a USARTx_CK pin. That's just shoddy work on their part. OP shouldn't care about that though since OP wants to use it in asynchronous which they can all do if you just leave the clock disabled. \$\endgroup\$ – DKNguyen Feb 19 '19 at 23:36
  • \$\begingroup\$ Found it, secton 2.2.23 is much more explicit about how many USART/UART modules there are and their clocking options. \$\endgroup\$ – DKNguyen Feb 19 '19 at 23:41

Can STM32F4 USART be used as UART?

Yes. A USART is a UART with an (optional) synchronous clock output.

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  • \$\begingroup\$ So can we say that in all I can have 4+2=6 UART ports on this MCU? \$\endgroup\$ – scico111 Feb 19 '19 at 23:35
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    \$\begingroup\$ Yes. There are a total of six UART peripherals, four of which support additional USART-only features. \$\endgroup\$ – duskwuff -inactive- Feb 19 '19 at 23:37
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    \$\begingroup\$ Yes, section 2.2.23 is much more explicit. In general, don't read too much into those feature tables. Look deeper into the datasheet. \$\endgroup\$ – DKNguyen Feb 19 '19 at 23:40

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