aboutsummaryrefslogtreecommitdiff
path: root/docs/drivers/i2c.md
diff options
context:
space:
mode:
Diffstat (limited to 'docs/drivers/i2c.md')
-rw-r--r--docs/drivers/i2c.md94
1 files changed, 63 insertions, 31 deletions
diff --git a/docs/drivers/i2c.md b/docs/drivers/i2c.md
index 2ef7afccc9..ad74d0e481 100644
--- a/docs/drivers/i2c.md
+++ b/docs/drivers/i2c.md
@@ -16,17 +16,22 @@ You can then call the I2C API by including `i2c_master.h` in your code.
## I2C Addressing {#note-on-i2c-addresses}
-All of the addresses expected by this driver should be pushed to the upper 7 bits of the address byte. Setting
-the lower bit (indicating read/write) will be done by the respective functions. Almost all I2C addresses listed
-on datasheets and the internet will be represented as 7 bits occupying the lower 7 bits and will need to be
-shifted to the left (more significant) by one bit. This is easy to do via the bitwise shift operator `<< 1`.
+I2C addresses listed on datasheets and the internet are usually represented as a 7-bit value. The eighth bit (the least significant bit) controls whether the operation is a read or a write.
-You can either do this on each call to the functions below, or once in your definition of the address. For example, if your device has an address of `0x18`:
+All of the address parameters expected by the driver API should therefore be pushed to the upper 7 bits of the address byte; the driver will take care of setting the read/write bit as appropriate.
+
+This is easy to do via the bitwise left shift operator. For example, if your device has an address of `0x18` you might create a define for convenience:
```c
#define MY_I2C_ADDRESS (0x18 << 1)
```
+Or, you can shift the address ahead of time:
+
+```c
+#define MY_I2C_ADDRESS 0x30
+```
+
See https://www.robot-electronics.co.uk/i2c-tutorial for more information about I2C addressing and other technical details.
## AVR Configuration {#avr-configuration}
@@ -39,12 +44,12 @@ The following defines can be used to configure the I2C master driver:
No further setup is required - just connect the `SDA` and `SCL` pins of your I2C devices to the matching pins on the MCU:
-|MCU |`SCL`|`SDA`|
-|------------------|-----|-----|
-|ATmega16/32U4 |`D0` |`D1` |
-|AT90USB64/128 |`D0` |`D1` |
-|ATmega32A |`C0` |`C1` |
-|ATmega328/P |`C5` |`C4` |
+|MCU |`SCL`|`SDA`|
+|-------------|-----|-----|
+|ATmega16/32U4|`D0` |`D1` |
+|AT90USB64/128|`D0` |`D1` |
+|ATmega32A |`C0` |`C1` |
+|ATmega328/P |`C5` |`C4` |
::: tip
The ATmega16/32U2 does not possess I2C functionality, and so cannot use this driver.
@@ -52,7 +57,7 @@ The ATmega16/32U2 does not possess I2C functionality, and so cannot use this dri
## ChibiOS/ARM Configuration {#arm-configuration}
-You'll need to determine which pins can be used for I2C -- a an example, STM32 parts generally have multiple I2C peripherals, labeled I2C1, I2C2, I2C3 etc.
+You'll need to determine which pins can be used for I2C -- as an example, STM32 parts generally have multiple I2C peripherals, labeled I2C1, I2C2, I2C3 etc.
To enable I2C, modify your board's `halconf.h` to enable I2C, then modify your board's `mcuconf.h` to enable the peripheral you've chosen:
@@ -83,15 +88,19 @@ To enable I2C, modify your board's `halconf.h` to enable I2C, then modify your b
Configuration-wise, you'll need to set up the peripheral as per your MCU's datasheet -- the defaults match the pins for a Proton-C, i.e. STM32F303.
-|`config.h` Overrride |Description |Default|
-|------------------------|--------------------------------------------------------------|-------|
-|`I2C_DRIVER` |I2C peripheral to use - I2C1 -> `I2CD1`, I2C2 -> `I2CD2` etc. |`I2CD1`|
-|`I2C1_SCL_PIN` |The pin definition for SCL |`B6` |
-|`I2C1_SCL_PAL_MODE` |The alternate function mode for SCL |`4` |
-|`I2C1_SDA_PIN` |The pin definition for SDA |`B7` |
-|`I2C1_SDA_PAL_MODE` |The alternate function mode for SDA |`4` |
+|`config.h` Override|Description |Default|
+|-------------------|-------------------------------------------------------------|-------|
+|`I2C_DRIVER` |I2C peripheral to use - I2C1 -> `I2CD1`, I2C2 -> `I2CD2` etc.|`I2CD1`|
+|`I2C1_SCL_PIN` |The pin to use for SCL |`B6` |
+|`I2C1_SCL_PAL_MODE`|The alternate function mode for SCL |`4` |
+|`I2C1_SDA_PIN` |The pin to use for SDA |`B7` |
+|`I2C1_SDA_PAL_MODE`|The alternate function mode for SDA |`4` |
+
+::: tip
+Currently only a single I2C peripheral is supported, therefore the `I2C1_*` defines are used for configuration regardless of the selected peripheral.
+:::
-The following configuration values depend on the specific MCU in use.
+The following configuration values are dependent on the ChibiOS I2C LLD, which is dictated by the microcontroller.
### I2Cv1 {#arm-configuration-i2cv1}
@@ -158,7 +167,7 @@ Send multiple bytes to the selected I2C device.
- `const uint8_t* data`
A pointer to the data to transmit.
- `uint16_t length`
- The number of bytes to write. Take care not to overrun the length of `data`.
+ The number of bytes to write. Take care not to overrun the length of `data`.
- `uint16_t timeout`
The time in milliseconds to wait for a response from the target device.
@@ -168,6 +177,29 @@ Send multiple bytes to the selected I2C device.
---
+### `i2c_status_t i2c_transmit_P(uint8_t address, const uint8_t* data, uint16_t length, uint16_t timeout)` {#api-i2c-transmit-p}
+
+Send multiple bytes from PROGMEM to the selected I2C device.
+
+On ARM devices, this function is simply an alias for `i2c_transmit(address, data, length, timeout)`.
+
+#### Arguments {#api-i2c-transmit-p-arguments}
+
+ - `uint8_t address`
+ The 7-bit I2C address of the device.
+ - `const uint8_t* data`
+ A pointer to the data to transmit.
+ - `uint16_t length`
+ The number of bytes to write. Take care not to overrun the length of `data`.
+ - `uint16_t timeout`
+ The time in milliseconds to wait for a response from the target device.
+
+#### Return Value {#api-i2c-transmit-p-return}
+
+`I2C_STATUS_TIMEOUT` if the timeout period elapses, `I2C_STATUS_ERROR` if some other error occurs, otherwise `I2C_STATUS_SUCCESS`.
+
+---
+
### `i2c_status_t i2c_receive(uint8_t address, uint8_t* data, uint16_t length, uint16_t timeout)` {#api-i2c-receive}
Receive multiple bytes from the selected I2C device.
@@ -177,9 +209,9 @@ Receive multiple bytes from the selected I2C device.
- `uint8_t address`
The 7-bit I2C address of the device.
- `uint8_t* data`
- A pointer to the buffer to read into.
+ A pointer to a buffer to read into.
- `uint16_t length`
- The number of bytes to read. Take care not to overrun the length of `data`.
+ The number of bytes to read. Take care not to overrun the length of `data`.
- `uint16_t timeout`
The time in milliseconds to wait for a response from the target device.
@@ -191,7 +223,7 @@ Receive multiple bytes from the selected I2C device.
### `i2c_status_t i2c_write_register(uint8_t devaddr, uint8_t regaddr, const uint8_t* data, uint16_t length, uint16_t timeout)` {#api-i2c-write-register}
-Writes to a register with an 8-bit address on the I2C device.
+Write to a register with an 8-bit address on the I2C device.
#### Arguments {#api-i2c-write-register-arguments}
@@ -202,7 +234,7 @@ Writes to a register with an 8-bit address on the I2C device.
- `const uint8_t* data`
A pointer to the data to transmit.
- `uint16_t length`
- The number of bytes to write. Take care not to overrun the length of `data`.
+ The number of bytes to write. Take care not to overrun the length of `data`.
- `uint16_t timeout`
The time in milliseconds to wait for a response from the target device.
@@ -214,7 +246,7 @@ Writes to a register with an 8-bit address on the I2C device.
### `i2c_status_t i2c_write_register16(uint8_t devaddr, uint16_t regaddr, const uint8_t* data, uint16_t length, uint16_t timeout)` {#api-i2c-write-register16}
-Writes to a register with a 16-bit address (big endian) on the I2C device.
+Write to a register with a 16-bit address (big endian) on the I2C device.
#### Arguments {#api-i2c-write-register16-arguments}
@@ -237,7 +269,7 @@ Writes to a register with a 16-bit address (big endian) on the I2C device.
### `i2c_status_t i2c_read_register(uint8_t devaddr, uint8_t regaddr, uint8_t* data, uint16_t length, uint16_t timeout)` {#api-i2c-read-register}
-Reads from a register with an 8-bit address on the I2C device.
+Read from a register with an 8-bit address on the I2C device.
#### Arguments {#api-i2c-read-register-arguments}
@@ -260,7 +292,7 @@ Reads from a register with an 8-bit address on the I2C device.
### `i2c_status_t i2c_read_register16(uint8_t devaddr, uint16_t regaddr, uint8_t* data, uint16_t length, uint16_t timeout)` {#api-i2c-read-register16}
-Reads from a register with a 16-bit address (big endian) on the I2C device.
+Read from a register with a 16-bit address (big endian) on the I2C device.
#### Arguments {#api-i2c-read-register16-arguments}
@@ -283,16 +315,16 @@ Reads from a register with a 16-bit address (big endian) on the I2C device.
### `i2c_status_t i2c_ping_address(uint8_t address, uint16_t timeout)` {#api-i2c-ping-address}
-Pings the I2C bus for a specific address.
+Ping the I2C bus for a specific address.
-On ChibiOS a "best effort" attempt is made by reading a single byte from register 0 at the requested address. This should generally work except for I2C devices that do not not respond to a register 0 read request, which will result in a false negative result (unsuccessful response to ping attempt).
+On ChibiOS a "best effort" attempt is made by reading a single byte from register 0 at the given address. This should generally work except for I2C devices that do not not respond to a register 0 read request, which will result in a false negative result (unsuccessful response to ping attempt).
This function is weakly defined, meaning it can be overridden if necessary for your particular use case.
#### Arguments {#api-i2c-ping-address-arguments}
- `uint8_t address`
- The 7-bit I2C address of the device (ie. without the read/write bit - this will be set automatically).
+ The 7-bit I2C address of the device.
- `uint16_t timeout`
The time in milliseconds to wait for a response from the target device.