Device Functions
Danger
This is historical documentation, and tooling and console operations are no longer available.
Microvisor system calls currently include the following functions for device-oriented operations:
Device Information Functions
Device State Functions
Device Clock Functions
Peripheral-Register Access Functions
Return Values and Errors
All of the functions described below return a 32-bit integer that is one of the values from the standard Microvisor enumeration MvStatus. All possible error values for a given system call are provided with each function’s description.
Success is always signaled by a return value of zero (MV_STATUS_OKAY).
mvGetDeviceId()
Get the device’s unique SID
Declaration
extern enum MvStatus mvGetDeviceId(uint8_t *buffer,
uint32_t length);
Parameters
Parameter |
Description |
|---|---|
|
A pointer to non-secure memory into which the device ID will be written by Microvisor |
|
The size of the buffer in bytes. Must be 34 |
Possible Errors
Error Value |
Description |
|---|---|
|
|
|
|
Description
Every Microvisor-enabled device has associated with it a unique 34-character identifier called an SID. This is set during the production of the microcontroller containing Microvisor. Use this function to read the SID, which can then be used to identify the device in your interactions with the Microvisor Cloud. You may also use it for device identification purposes within your own cloud and mobile apps.
Although the SID is output as Ascii text, it is not a C string. To use the SID characters with C string-manipulation functions, and printf(), ensure your buffer is 35 characters long and terminated with a nul ('\0').
Example
uint8_t buffer[35] = { 0 };
mvGetDeviceId(buffer, 34);
printf("Device ID: %s\n", buffer);
mvRestart()
Restart the application and/or the device
Declaration
extern enum MvStatus mvRestart(enum MvRestartMode mode);
Parameters
Parameter |
Description |
|---|---|
|
The level of restart to perform |
Possible Errors
Error Value |
Description |
|---|---|
|
The call has been made from within an interrupt service routine (ISR) |
|
An unknown |
|
The restart cannot be performed because it will interrupt Microvisor’s |
Description
This call is typically made as part of an application’s support for polite deployment: the means by which it manages staged application and/or Microvisor updates at moments when the system restart the installation of these updates require would interrupt critical tasks being performed by the application. When polite deployment is enabled and the application is notified that an update has been downloaded and staged, it can defer installation if it needs to. When the application knows it is safe to proceed with installation, it calls MvRestart() to begin the installation process.
Currently, only one value of the mode parameter is available: MV_RESTARTMODE_AUTOAPPLYUPDATE. This will cause any update, whether of the application, Microvisor, or both, to be applied immediately via a reset. As such, the call will return only in the case of an error.
mvRestart() may not be called from within in interrupt service routine.
Note
For further guidance, please see the Microvisor polite deployment documentation
mvGetSysClk()
Get the current frequency of the CPU clock
Declaration
extern enum MvStatus mvGetSysClk(uint32_t *frequency);
Parameters
Parameter |
Description |
|---|---|
|
A pointer to non-secure memory into which the frequency will be written by Microvisor |
Possible Errors
Error Value |
Description |
|---|---|
|
|
mvGetHClk()
Get the current frequency of the microcontroller’s Advanced High-performance Bus (AHB)
Declaration
extern enum MvStatus mvGetHClk(uint32_t *frequency);
Parameters
Parameter |
Description |
|---|---|
|
A pointer to non-secure memory into which the frequency will be written by Microvisor |
Possible Errors
Error Value |
Description |
|---|---|
|
|
mvGetPClk1()
Get the current frequency of the microcontroller’s Advanced Peripheral Bus (APB1)
Declaration
extern enum MvStatus mvGetPClk1(uint32_t *frequency);
Parameters
Parameter |
Description |
|---|---|
|
A pointer to non-secure memory into which the frequency will be written by Microvisor |
Possible Errors
Error Value |
Description |
|---|---|
|
|
mvGetPClk2()
Get the current frequency of the microcontroller’s Advanced Peripheral Bus (APB2)
Declaration
extern enum MvStatus mvGetPClk2(uint32_t *frequency);
Parameters
Parameter |
Description |
|---|---|
|
A pointer to non-secure memory into which the frequency will be written by Microvisor |
Possible Errors
Error Value |
Description |
|---|---|
|
|
Register Access Functions
Microvisor includes a set of functions which provide application code with access to the contents of host microcontroller peripheral registers that are claimed by Microvisor. An example is reading the Reset and Clock Controller (RCC) configuration: this is needed by the application to determine the underlying clock speeds and so configure a peripheral, but RCC owned by Microvisor so that it can control key clocks.
Non-secure code, ie. the application, can’t directly read or write these registers, at least not in a way that yields unambiguous values. TrustZone ensures writes from non-secure code are always ignored and reads return zero, but does not inform the application that it has done so. Microvisor therefore provides mediated read and write access to these secure registers.
Warning
Attempts to access peripheral registers outside of these system calls are trapped by Microvisor, which treats them as illegal accesses and restarts the application. This is done to alert the developer, who can then modify their code to prevent the illegal access.
Microvisor maintains a list of registers that the application is able to access through these system calls. These are provided as non-secure mappings; Microvisor translates the value to a secure mapping. If the call does not provide access to a given register, the call returns an error value.
For each valid register, Microvisor also maintains masks of the bits that are readable and the bits that are writable by the application. Bits the application is not permitted to access are unset in reads and unchanged by writes.
Note
These system calls can be used for any register, including those that the application has non-secure access to. If the supplied address references a register that is implicitly accessible to the application, then Microvisor makes the access directly on the non-secure mapping. This is as if the application made the access itself. A consequence of this is that you can use these calls in your cade consistently across all register access operations.
mvPeriphPeek32()
Read the contents of a device peripheral register
Declaration
extern enum MvStatus mvPeriphPeek32(uint32_t *register,
uint32_t *register_value;
Parameters
Parameter |
Description |
|---|---|
|
The non-secure address of the register being accessed |
|
A pointer to non-secure memory into which the register’s contents will be |
Possible Errors
Error Value |
Description |
|---|---|
|
|
|
|
Description
This call reads the contents of one of the microcontroller’s peripheral registers and writes the result to non-secure memory.
Example
int64_t readRegisterOrNegOnError(uint32_t reg) {
uint32_t tmp = 0;
extern enum MvStatus status = mvPeriphPeek32(reg, &tmp);
return (status == MV_STATUS_OKAY ? (int64_t)tmp : -1);
}
mvPeriphPoke32()
Write data to a device peripheral register
Declaration
extern enum MvStatus mvPeriphPoke32(uint32_t *register,
uint32_t mask,
uint32_t xor_value);
Parameters
Parameter |
Description |
|---|---|
|
The non-secure address of the register being accessed |
|
A mask to indicate the bits that will be affected by the write |
|
A value to Exclusive OR with the register’s current contents |
Possible Errors
Error Value |
Description |
|---|---|
|
|
Description
Use this function to update the value held by a microcontroller peripheral register. The call can be used for a variety of different operations, from writing specific values to the register, to performing bit-level changes. The function applies the following logic to the value of the chosen register:
*register = (*register & ~mask) ^ xor_value
and with appropriate mask and XOR values, these operations are possible:
Operation |
Mask Value |
XOR Value |
|---|---|---|
Clear bits |
Bits to clear |
|
Set bits |
Bits to set |
Bits to set |
Toggle bits |
|
Bits to Set |
Change the whole register |
|
New value |