To adapt PScript to the current platform I add an interface to add “built-in” content and a C++ library with some content prepared. This is to make PScript as scalable as possible as built-in content needs to be platform specific and depending on how much Flash/SRAM that is available.
Records
Records are bit-packed and can have fixed addresses making them excellent to overlay IO registers. This open for two types of interface to hardware – one there PScript go low level through pre-defined records and a more abstract interface through functions.
PScript is not object oriented, but to access HW IO we use record names as prefix separated with a “.” (dot) as we would have done if record was object variables.
Example:
GPIOA.pinMode(1, OUTPUT, PULLDOWN)
while true
GPIOA.digitalWrite(0, HIGH)
Sleep(500)
GPIOA.digitalWrite(0, LOW)
Sleep(500)
end
|
This example will toggle GPIOA, pin 0 high/low at ca 1Hz frequency.
To support this I will need (1) a method to add constants like OUTPUT, PULLDOWN etc, (2) a method to add records and a method to add functions with and without object reference. I will return to this as I discuss PScript API. Focusing on records and functions I plan the following list. Arduino have a well designed interface, so using that as a starting guideline will be good. This proposal is based on STM32F405RG, so low level content like registers will differ from MCU to MCU.
Records
| GPIOA, GPIOB, GPIOC, GPIOD, GPIOE, GPIOF etc | GPIO ports with member variables to match registers on MCU. |
| ADC1, ADC2, ADC3 | Analogue to digital conversion. |
| Serial1, Serial2, Serial3, Serial4, Serial5, Serial6 | Serial ports. |
| SPI1, SPI2, SPI3 | SPI ports |
| I2C1, I2C2, I2C3 | I2C ports |
| DAC1, DAC2 | Digital to Analogue conversion. |
| RTC | Real Time Clock |
| TIM1 to TIM14 | HW Timers |
| USB | USB |
| CAN1, CAN2 | CAN ports |
| I2S1, I2S3 | I2S ports |
| RNG | Random Number Generator |
| CRC | CRC |
| ETC | Elapsed Timer |
The only records I am holding back on are some of the core content like clock, dma and wathdogs etc as I will cover those differently. I need to evaluate a bit as I go.
The records are as mentioned MCU specific due to their content, but the interface functions are designed to be portable with one exception – pinMode will be MCU specific. The list below is a brief intro – I will describe syntax and modules in more details later.
| pinMode | Define what we use a specific pin for. |
| digitalWrite | Set GPIO pins |
| digitalRead | Read GPIO pins |
| analogRead | ADC |
| analogWrite | DAC |
| serial1.Open | Open a serial port. Both USB, Serial, SPI, I2C, CAN and I2S can be treated as serial ports with a bytes in/out concept. |
| serial1.Close| | Close a serial port |
| serial1.Send | Send bytes on a serial port |
| serial1.Receive | Receive bytes on a serial port |
| tim1.start | Start a timer |
| tim1.stop | Stop a timer |
| rtc.SetTime | Set time |
| rtc.GetTime | Get current time |
| rtc.SetAlarm | Set alarm clock |
| etc.millis | Get elapsed time in ms. |
| etc.micros | Get elapsed time in micro seconds. |
| rtos.StartThread | Start a function as a thread. |
| rtos.StopThread | Stop a function as a thread |
| rtos.Lock | Lock processing to this thread |
| rtos.Unlock | Unlock so threads/events can execute |
| print, println | Print and print line |
| math | Math functions like cos, tan, sin etc. |
The list will be evaluated and subject for changes. The objective is to provide some functionality to PScript, but at the same time avoid making the package to large.