Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Jump to bottom

Update UART programmers guide #1357

Merged
merged 1 commit into from
Nov 3, 2024
Merged

Update UART programmers guide #1357

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
23 changes: 13 additions & 10 deletions doc/src/programmers-guide.md
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -1716,34 +1716,37 @@ Information about the ESP32 UART interface can be found in the IDF SDK [UART Doc

The AtomVM UART implementation uses the AtomVM Port mechanism and must be initialized using the [`uart:open/2`](./apidocs/erlang/eavmlib/uart.md#open2) function.

The first parameter indicates the ESP32 UART hardware interface. Legal values are:
The first parameter indicates the ESP32 UART hardware interface. Valid values are:

```erlang
"UART0" | "UART1" | "UART2"
```

The selection of the hardware interface dictates the default RX and TX pins on the ESP32:

| Port | RX pin | TX pin |
|-------------|--------|-------|
| `UART0` | GPIO_3 | GPIO_1 |
| `UART1` | GPIO_9 | GPIO_10 |
| `UART2` | GPIO_16 | GPIO_17 |

The second parameter is a properties list, containing the following elements:

| Key | Value Type | Required | Default Value | Description |
|-----|------------|----------|---------------|-------------|
| `rx` | `integer()` | no | -1 (`UART_PIN_NO_CHANGE`) | RX GPIO Pin |
| `tx` | `integer()` | no | -1 (`UART_PIN_NO_CHANGE`) | TX GPIO Pin |
| `speed` | `integer()` | no | 115200 | UART baud rate (bits/sec) |
| `data_bits` | `5 \| 6 \| 7 \| 8` | no | 8 | UART data bits |
| `stop_bits` | `1 \| 2` | no | 1 | UART stop bits |
| `flow_control` | `hardware \| software \| none` | no | `none` | Flow control |
| `parity` | `even \| odd \| none` | no | `none` | UART parity check |


These are the usual RX and TX pins for the various UARTs on the ESP32 (as always check your board specs):

| Port | RX pin | TX pin |
|-------------|--------|-------|
| `UART0` | GPIO_3 | GPIO_1 |
| `UART1` | GPIO_9 | GPIO_10 |
| `UART2` | GPIO_16 | GPIO_17 |

For example,

```erlang
UART = uart:open("UART0", [{speed, 9600}])
UART = uart:open("UART0", [{rx, 3}, {tx, 1}, {speed, 9600}])
```

Once the port is opened, you can use the returned `UART` instance to read and write bytes to the attached device.
Expand Down